T •

U. S. DEPARTMENT OF COMMERCE
BUILDING MATERIALS AND STRUCTURES REPORTS

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BMSl Research on Building Materials and Structures for Use in Low-Cost Housing 100 BMS2 Methods of Determining the Structural Properties of Low-Cost House Constructions.. 100 BMS3 Suitability of Fiber Insulating Lath as a Plaster Base 100 BMS4 Accelerated Aging of Fiber Building Boards 100 BMS5 Structural Properties of Six Masonrv Wall Constructions 150 BMS6 Survey of Roofing Materials in the Southeastern States 150 BMS7 Water Permeability of Masonry Walls 100 BMS8 Methods of Investigation of Surface Treatment for Corrosion Protection of Steel 100 BMS9 Structural Properties of the Insulated Steel Construction Co.'s "Frameless-Steel" Constructions for Walls, Partitions, Floors, and Roofs 100 BMS10 Structural Properties of One of the "Keystone Beam Steel Floor" Constructions Sponsored by the H. H. Robertson Co 100 BMS11 Structural Properties of the Curren Fabrihome Corporation's "Fabrihome" Constructions for Walls and Partitions 10^ BMS12 Structural Properties of "Steelox" Constructions for Walls, Partitions, Floors, and Roofs

Sponsored by Steel Buildings, Inc 150 BMS13 Properties of Some Fiber Building Boards of Current Manufacture 100 BMS14 Indentation and Recovery of Low-Cost Floor Coverings 100 BMS15 Structural Properties of "Wheeling Long-Span Steel Floor" Construction Sponsored by

Wheeling Corrugating Co 100 BMS16 Structural Properties of a "Tilecrete" Floor Construction Sponsored by Tilecrete Floors, Inc 100 BMS17 Sound Insulation of Wall and Floor Constructions 100 Supplement to BMS17, Sound Insulation of Wall and Floor Constructions 50 BMS18 Structural Properties of "Pre-Fab" Constructions for Walls, Partitions, and Floors Sponsored by the Harnischfeger Corporation 100 BMS19 Preparation and Revision of Building Codes 150 BMS20 Structural Properties of "Twachtman" Constructions for Walls and Floors Sponsored by

Connecticut Pre-Cast Buildings Corporation 100 BMS21 Structural Properties of a Concrete-Block Cavity-Wall Construction Sponsored by the National Concrete Masonry Association 100 BMS22 Structural Properties of "Dun-Ti-Stone" Wall Construction Sponsored by the W. E. Dunn Manufacturing Co 100 BMS23 Structural Properties of a Brick Cavity-Wall Construction Sponsored by the Brick

Manufacturers Association of New York, Inc 100 BMS24 Structural Properties of a Reinforced-Brick Wall Construction and a Brick-Tile CavityWall Construction Sponsored by the Structural Clay Products Institute — 100 BMS25 Structural Properties of Conventional Wood-Frame Constructions for Walls, Partitions,

Floors, and Roofs 150 BMS26 Structural Properties of "Nelson Pre-Cast Concrete Foundation" Wall Construction

Sponsored by the Nelson Cement Stone Co., Inc 100 BMS27 Structural Properties of "Bender Steel Home" Wall Construction Sponsored by The

Bender Body Co 100 BMS28 Backflow Prevention in Over-Rim Water Supplies 100 BMS29 Survey of Roofing Materials in the Northeastern States 100 BMS30 Structural Properties of a Wood-Frame Wall Construction Sponsored by the Douglas

Fir Plywood Association 100 BMS31 Structural Properties of "Insulite" Wall and "Insulite" Partition Construction Sponsored by The Insulite Co 150 BMS32 Structural Properties of Two Brick-Concrete-Block Wall Constructions and a Concrete- Block Wall Construction Sponsored by the National Concrete Masonry Association, 100 BMS33 Plastic Calking Materials 100 BMS34 Performance Test of Floor Coverings for Use in Low-Cost Housing: Part 1 100 BMS35 Stability of Sheathing Papers as Determined by Accelerated Aging 100 BMS36 Structural Properties of Wood-Frame Wall, Partition, Floor, and Roof Constructions with

"Red Stripe" Lath Sponsored by The Weston Paper and Manufacturing Co 100 BMS37 Structural Properties of "Palisade Homes" Constructions for Walls, Partitions, and

Floors, Sponsored by Palisade Homes 100

[List continued on cover page III]
UNITED STATES DEPARTMENT OF COMMERCE . Jesse H. Jones, Secretary

NATIONAL BUREAU OF STANDARDS • Lyman J. Briggs, Director BUILDING MATERIALS

and STRUCTURES

REPORT BMS92

Fire-Resistance Classifications

of Building Constructions

Report of Subcommittee on Fire-Resistance Classifications

of the

Central Housing Committee on Research, Design, and Construction

ISSUED OCTOBER 7, 1942

The National Bureau of Standards is a fact-finding organization;

it does not "approve" any particular material or method of construction. The technical findings in this series of reports are to be construed accordingly.

UNITED STATES GOVERNMENT PRINTING OFFICE • WASHINGTON • I942

FOR SALE BY THE SUPERINTENDENT OF DOCUMENTS, WASHINGTON, D. C. PRICE 25 CENTS
Forewo r d

The object of this report is to present a classification of building construction

based on essential features having a bearing on the restricting and retarding effect on

fire offered by the different types. The classes within each type are differentiated by

the degree of fire resistance of structural members. As an assistance in applying these

classifications, data are included from surveys of combustible contents of buildings

and from fire tests of building constructions and materials conducted at this Bureau

and other laboratories. The report should be of value in presenting building classifica- tions and pertinent related data on the basis of which restrictions on size, location,

and structural components of buildings can be applied to give a required degree of safety

with the economical use of a wide range of acceptable materials.

Lyman J. Briggs, Director.

fn]
Fire-Resistance Classifications of Building Materials

Report of Subcommittee on Fire-Resistance Classifications of the Central Housing

Committee on Research, Design, and Construction

John W. Dunham, Chairman, William J. O'Connor, Vice-Chairman,

Public Buildings Administration. Federal Housing Administration.

S. H. Ingberg, Technical Adviser to Subcommittee,

National Bureau of Standards.

Bert M. Thorud, Charles N. Diener,

United States Housing Authority. Home Owners' Loan Corporation.

With Acknowledgement to Previous Members of the Subcommittee

Colin O. Skinner, Howard S. Gay,

United States Housing Authority. Public Works Administration.

and to

Martin Goerl, John C. Lamb,

National Bureau of Standards. United States Housing Authority.

Mary Fidelia Taylor,

Secretary.

ABSTRACT

A classification of building construction from the standpoint of fire safety is presented by a committee

of representatives of Federal agencies concerned with

the design, construction, and operation of buildings.

By considering only the basic properties having a bearing on fire hazard and fire resistance, four types were found sufficient to cover the whole range of building

construction. Within each type are two or more classes which are defined by the fire resistance required for

their structural members. In chapter I this classifica- tion is outlined and information given on how it can be

applied with reference to the fire severity obtaining for

given structural and occupancy conditions. Chapter

II contains a discussion of the types of restrictions and

limitations generally incorporated in building codes,

with particular reference to their application to the

classification of building types herein presented.

Chapter III gives results of surveys of combustible

contents of buildings housing typical occupancies as a

basis for estimation of fire severity, In chapter IV

are given available fire-resistance ratings of building

constructions and fire-resistance classifications of roof- ing materials.

[1]
CONTEN T

S

Page

Foreword n

Introduction 4 Chapter I. A fire-resistance classification of building types 5

1. Types of construction 6

(a) Type I. Fireproof construction 6

(b) Type II. Incombustible construction. 7

(c) Type III. Exterior-protected construction 8

(d) Type IV. Wood construction 9

2. Fire severity 9

3. Fire-resistance ratings 10 Chapter II. Restrictions and limitations in their relation to types of construction . . 10

1. Location with respect to fire zones 11

2. Restrictions based on height of building. _ 11

(a) Fireproof construction 12

(b) Incombustible construction 12

(c) Exterior-protected construction 13

(d) Wood construction ; — 14

3. Restrictions on location with respect to common property lines or adjacent

buildings construction 14

4. Restrictions based on area of building 16

(a) Fireproof construction 16

(b) Incombustible construction 17

(c) Exterior-protected construction 17

(d) Wood construction 17

5. Restrictions on type of materials in building members and building finish 18

6. Restrictions based on degree of fire resist- ance of structural members 19

7. Restrictions based on occupancy 19 Chapter III. Survey of combustible contents of buildings 20 Chapter IV. Fire-resistance ratings for building construction and materials 25

1. Fire-resistance ratings for load-bearing

masonry walls : 25

(a) Test conditions 25

(b) Sources of data 26

(c) Extension and interpolation of test results 26

(d) Effect of plaster 26

(e) Combustible members framed into wall 27

(f) Fire-resistance ratings 27

2. Fire-resistance ratings for masonry parti- tions 29

(a) Test conditions 29

(b) Sources of data 29

(1) Magnesium oxysulfate woodfiber blocks 29

(2) Hollow glass blocks 29

(3) Gypsum blocks 29

(4) Structural clay tile 29

(5) Hollow concrete units 29

(c) Fire-resistance ratings 30

Page

Chapter IV. Fire-resistance ratings for building construction and materials—Continued

3. Fire-resistance ratings for steel-framed

partitions and steel-framed brick-ve- neered walls 31

(a) Test conditions 31

(b) Source of data 31

(c) Plaster 31

(d) Fire-resistance ratings 31

4. Fire-resistance ratings for wood- and metal- framed partitions 32

(a) Test conditions 32

(b) Sources of data 32

(c) Interpolation of test results 32

(d) Framing 32

(1) Wood framing 32

(2) Metal-framed, hollow parti- tions 32

(3) Metal-framed, solid parti- tions 32

(e) Firestopping 33

(f) Mineral-wool fill 33

(g) Board facings and plaster bases 33

(h) Plaster 33

(i) Fire-resistance ratings 33

(j) Partition facings as fire-protective

finishes over wood framing 35

5. Fire-resistance ratings for walls and parti- tions with cement-asbestos facings 35

(a) Test conditions 35

(b) Source of data 35

(c) Firestopping 35

(d) Fire-resistance ratings 35

(e) Facings as fire-protective finishes over wood framing 35

6. Fire-resistance ratings for prefabricated

and built-up partitions 36

(a) Test conditions 36

(b) Sources of data. _ . 36

(c) Assembly of prefabricated wood

panels 36

(d) Flameproofing 36

(e) Load-carrying ability of built-up

and prefabricated wood or steel partitions 36

7. Fire-resistance ratings for columns 37

(a) Test conditions 37

(b) Effect of plaster 37

(c) Sources of data - 37

(1) Timber columns 37

(2) Round cast iron columns 37

(3) Steel pipe columns 37

(4) Structural steel columns (unprotected) 37

(5) Structural steel (solid section) partly protected with

concrete 37

[2]
Page

Chapter IV. Fire-resistance ratings for building construction and materials—Continued

7. Fire-resistance ratings for columns—Con.

(c) Sources of data—Continued

(6) Structural - steel (latticed) partly protected with concrete 37

(7) Structural steel solidly protected with concrete 37

(8) Structural steel protected

with hollow tile and concrete 38

(9) Structural steel protected

with hollow tile 38

(10) Structural steel protected

with brick 38

(11) Structural steel protected

with hollow cinder concrete blocks 38

(12) Structural steel protected

with plaster 38

(13) Structural steel protected

with gypsum 38

(14) Reinforced concrete col- umns 38

(d) Fire-resistance ratings 38

8. Fire-resistance ratings for floor constructions 40

(a) Test conditions 40

(b) Source of data 40

(c) Plaster 40

(d) Fire-resistance ratings for woodjoist floors 40

(e) Fire-resistance ratings for steeljoist floors 41

(f) Fire-resistance ratings for steel- plate floors 41

(g) Fire-resistance ratings for cellular

steel floors 42

9. Fire-resistance classification of roof coverings 43

(a) Basis of classification 43

(b) Sources of data 43

(c) General requirements 43

(d) Lists of acceptable roof coverings 44

(1) Built-up roof coverings 44

(2) Prepared roof coverings 45

Appendix A. Summary of restrictions and limi- tations in six typical building codes based on types of construction:

I. Classifications 48

1. New York:

(a) Classification of structures by

type of construction 48

(b) Classification by occupancy.. 48

2. Boston:

(a) Types of construction 48

(b) Occupancies classified 48

Tage

Appendix A. Summary of restrictions and limi- tations in six typical building codes based on types of construction- Con.

I. Classifications—Continued

3. Minneapolis:

(a) Types of construction 48

(b) Classification of buildings_ _„_ 49

4. Atlanta:

(a) Classification of buildings by

construction . 49

(b) Classification of buildings by

occupancy 49

5. Denver:

(a) Types of construction 49

(b) Occupancy classification 49

6. Seattle:

(a) Types of construction 50

(b) Occupancy classification 50

II. Location with respect to fire zones 50

1. Number of zones, including an unrestricted area 50

2. Restrictions and limitations:

(a) New York 50

(b) Boston 50

(c) Minneapolis 50

(d) Atlanta 50

(e) Denver 50

(f) Seattle 50

III. Permissible spacing from adjacent construction or property lines 51

1. New York 51

2. Boston 51

3. Minneapolis 51

4. Atlanta . 52

5. Denver 52

6. Seattle *_ 52

IV. Permissible heights and areas of build- ings 52

1. New York 52

2. Boston 53

3. Minneapolis 55

(a) Height limitation 55

(b) Area or combined height and

area limitations 55

4. Atlanta 56

(a) Heights of buildings 56

(b) Allowable floor areas 56

(c) Frame buildings outside of

fire limits 57

5. Denver 57

(a) Restrictions based on types

of construction 57

(b) Restrictions based on occu- pancy 57

6. Seattle 58

(a) Maximum building heights. _ 58

(b) Maximum building areas 58

V. Permissible materials 59

1. New York 59

2. Boston 60

[3]
Page

Appendix A. Summary of restrictions and limi- tations in six typical building codes based on types of construction—Con.

V. Permissible materials—Continued

3. Minneapolis 61

4. Atlanta 62

5. Denver 63

6. Seattle 63

VI. Required degree of fire resistance of structural members 65

1. New York 65

2. Boston 65

3. Minneapolis 65

4. Atlanta 65

5. Denver 65

6. Seattle 66

VII. Permissible occupancies 66 h New York 66

2. Boston 66

3. Minneapolis 66

4. Atlanta - 66

5. Denver 66

6. Seattle 67 Appendix A. Summary of restrictions and limi- tations in six typical building codes based on types of construction—Con.

Page

VIII. Discussion of current building code restrictions in their relat ion to types of construction 67

1. Classification of buildings by type

of construction 67

2. Occupancy classifications 67

3. Fire zoning 67

4. Spacing from adjacent construction

or property line 67

5. Height and area limitations 67

6. Permissible materials 68

7. Required fire resistance 68

8. Permissible occupancies 68

Appendix B. Methods of estimating fire-resis- tance periods 69

Section 1. General method of estimating the ultimate fire-resistance periods of walls and partitions 69

Section 2. General method of estimating

the ultimate fire-resistance periods of columns 69

(a) Protected metal columns 70

(b) Reinforced concrete columns. 70

Section 3. Applications made in the present

report _• 70 INTRODUCTION

The purpose of this report is to present to

architects, engineers, and public officials re- sponsible for fire safety in buildings, a classifi- cation of building constructions which repre- sents the recommendations of the Subcommittee, a discussion thereof, and certain factual

data which have been assembled by the Subcommittee. The report is not proposed as a

fire-protection section of a building code, but

it is intended to indicate some of the changes

from current practice that should be considered

in writing or revising building codes and to supply some of the factual data necessary to a proper consideration of the changes indicated.

It appears desirable that codes should be

written to permit the use of new systems of

construction where they can be demonstrated

to be comparable in performance to the systems

now described in current codes in terms of materials.

The Subcommittee believes that the idea of designing some buildings for the full fire severity

corresponding to the occupancy and others for a given established fire resistance, is a logical

advance in fire protection engineering. It

offers no more complications as regards possible occupancy changes and code requirements

than does the idea of designing buildings for predetermined live loads. For example, buildings designed for residential use with live loads

in the neighborhood of 40 lb/ft2 cannot be used

for heavy mercantile occupancy, and it is illogical to require them to be designed for the same fire severity.

The subdivision of types of construction is proposed in order to embrace the useful range

of resistance that is obtainable within each type

and to provide a convenient means of designating the position of a particular construction

within that range. Chapter I offers a classification of building

types from the standpoint of fire safety. The

relations between combustible contents, fire severity, and fire-resistance ratings are outlined

and a method of evaluating the combustible

contents of a building is given.

Chapter II contains a discussion of the re- strictions and limitations which experience indi- cates should be applied to buildings with respect

to occupancy and construction for the purpose

of limiting the use of the several constructions

to situations in which a satisfactoiy degree of

[4]
safety from fire can be attained economically.

The discussion is supplemented by the illus- trative summary of restrictions and limitations on construction in six typical building codes,

which comprise appendix A. They are pre- sented as giving a typical cross section of cur- rent building codes, not necessarily ideal nor

illustrative of the recommendations of the

Subcommittee.

Chapter III summarizes the findings of ac- tual surveys of combustible contents of buildings for a number of typical occupancies. This

material is considered to be a reliable guide in

making an estimate of the probable combustible

contents of projected occupancies similar to those surveyed.

Chapter IV presents a tabulation of fire- resistance ratings for building constructions and

materials. Derivations of the values are indicated in that chapter and in appendix B. This

tabulation is for use in selecting constructions

that will fulfill the given requirements and

enables a choice to be made in a range of constructions having a required fire-resistance

rating.

For definitions of terms used in this reportreference is made to BMS91, A Glossary of

Housing Terms (1942).

CHAPTER I. A FIRE-RESISTANCE CLASSIFICATION OF BUILDING TYPES

The fire-resistance classifications of building

types heretofore generally have been defined in terms of established constructions and materials.

The classification contained in this chapter is based on performance in fires and fire tests, graduated within each type. Materials are

differentiated only as regards combustibility or incombustibility

.

The Fireproof type includes all buildings of incombustible structure which will either withstand complete combustion of their contents

without collapse or which will have a general

fire-resistance rating of 4 hr and in addition

other safeguards designed to prevent a more

severe fire. Within this type, the classification

is such that a building may be designed to have

a fire resistance corresponding to the fire severity that may be created by the occupancy.

This eliminates the common practice of requiring a uniform fire resistance for all Fireprooftype buildings, which results in excessive resist- ance for occupancies having light combustible

contents and insufficient resistance where the

combustible contents are very heavy. Economies are thus made possible in the former case and increased protection is required in the

latter for buildings classed as Fireproof.

It is assumed that in setting the required

degree of fire resistance for Fireproof buildings,

due consideration will be given to possible

changes in occupancy and tenancy that may

increase the amount of combustibles above that

estimated for the occupancy immediately con- templated, this applying particularly to manufacturing, mercantile, and storage buildings.

As a further control, the fire rating of floors in such buildings can be posted, as is now being

done for permissible loading. A higher fire resistance for the lower floor or floors may also be in order for construction such as office buildings and apartment buildings in commercial districts, considering possible use for mercantile and similar occupancies. The sur- veys (chapter III) also indicate a large range

in combustible contents of office buildings,

depending on the relative amount of space

used for record filing and storage and the type

of equipment provided for the purpose. The

effective fire exposure from paper records is greatly decreased with incombustible containers (see page 10).

For buildings or portions of buildings used

for residential purposes, the combustible contents were found to be uniformly within the

low range. Even with concentrated furniture

storage, they were equivalent to no more than

15 lb /ft2. The same applies for schools and

hospitals except for small storage areas usually

in basements. Such buildings and others

housing occupancies corresponding to them in

combustible contents can be regarded as strictly

Fireproof provided the protection is adequate

for the fire hazard presented even if the construction is rated no more than 1 hr. The

damage from fires in such buildings will be

largely to contents and building finish, although

damage not causing collapse of any structural

member may occur. As a further safeguard,

Fireproof buildings with the lower fire ratings
can be limited in height so that if any subsequent use should result in greater fire severity

they would present no greater hazard than

buildings of nonfireproof types.

The three other types are each subdivided

into two classes which with differentiation in

height and area limitations will assist in obtaining safe and economical application for each

type. The %-hr limit was chosen for the A

class, since it is attainable with less exacting

details of protection than the 1-hr rating and is near the maximum practically attainable with

types III and IV, considering the possibility

of spread of fire at junctions of floor, wall, and

partition constructions.

The Incombustible type covers the range of buildings of incombustible structure from unprotected construction to that having a general

fire-resistance rating of % hr. Although this construction will not of itself contribute to a

fire, structural collapse should be expected in a fire of severity exceeding that indicated by

the titles of the subtype.

The Exterior-Protected type covers the range

from ordinary masonry wall and wood-joist

construction to and including mill construction.

A fire in this type of building will eventually

involve the structural members and produce

collapse unless extinguished. The general rat- ings given in the titles of the subtypes indicate a time within which extinguishment might be

expected to prevent collapse.

Wood construction has been extended to include combustible constructions having considerable fire resistance. The remarks in regard

to the Exterior-Protected type also apply to

this type.

Although no requirements for exterior protection are indicated for the Incombustible and

Wood construction type buildings, it is assumed

that they will be restricted in location with

respect to common property lines unless such

protection is provided. If Incombustible buildings are built to a property line on which

another building can be built, it would be in

accord with requirements for Fireproof and

Exterior-Protected buildings to require 2-hr

exterior protection. The requirements for exterior protection and location with respect to common property lines should also take into

account the size of the building in making

allowance for the lower hazard from small

structures such as private garages.

The party- and fire-wall requirements for buildings of the nonfireproof types are in- tended to afford protection to the construction on one side after collapse from fire on the other

side and ensuing prolonged fire and heat ex- posure from burning debris. The thicknesses

needed are in most cases no more than required

for stability even as supported by the construction framed in on the unexposed side. For a given amount of combustible contents the

requirements for the Incombustible type are higher than for the Exterior-Protected and

Wood construction types, since the incombustible floor constructions after collapse tend

to confine the heat from the burning debris and

cause prolonged fire exposure on a proportionately greater height above the base of the wall.

1. Types of Construction

The following definitions divide buildings

into types with respect to fire resistance as follows

Type I. Fireproof construction.

Type II. Incombustible construction.

Type III. Exterior-Protected construction.

Type IV. Wood construction.

The requirements for roof covering set forth

herein are to be regarded as the minima for the

several building types. Where a* higher class

is required by the local fire zoning, the covering

of such higher class shall be applied. The

relation of combustible contents to fire severity

is indicated on page 7.

(a) Type I. Fireproof Construction

That type of construction in which the

structural elements are of incombustible materials with fire-resistance ratings sufficient to withstand the fire severity resulting from complete combustion of the contents and finish in- volved in the intended occupancy but not less than the rating specified in table 1, and for

which the roof coverings are as specified

hereafter.

[6]
Table 1.—Minimum fire-resistance ratings of structural elements for type I construction

Subtype I-A IB I-C I-D I-E I-F

General fire-resistance rating in hours Over

4 4 3 2 V/z 1

Weight of combustibles, lb/ft 2 Over

of floor area 35 35 30 20 15 10

Exterior walls—outside exposure: Distance from common property-line or other buildings on the same property: Under 10 ft (including common-property-line hr hr hr hr hr hr

walls) 2 2 2 2 2 2 From 10 to 20 ft 1H l\i l]4 More than 20 ft 1 1 1 1 1 1 Exterior walls—inside exposure _ (») 4 3 2 m 1 Interior bearing walls ('») 4 3 2 m 1 Columns, girders, trusses (?) 4 3 2 m 1 Floor construction (" 4 3 2 1 Roof construction i> (*) 4 3 2 m. 1 Fire walls, fire division walls, and party walls 0 (») 4 3 2 2 2 Fire-resistive partitions. . 1 1 1 1 1 1 Interior partitions d enclosing: Public hallways - 1 1 1 1 1 1 Public stairways and other

vertical openings .__ 2 2 2

9 l'/2 1 Other permanent partitions (?) (-) (•) (?) (?) (•)

« When the combustible contents exceed 35 lb/ft2

: These structural elements shall be designed to have a fire-resistance rating sufficient to withstand the fire severity resulting from complete combustion of the contents; or These structural elements shall be designed to have fire-resistance ratings as indicated in table 1 for 35 lb/ft - and additional safeguards shall be provided in accordance with any one of the

following:

(1) The height shall be limited to 50 ft for warehouses and 75 ft for other buildings.

(2) The combustibles shall be placed wholly or partly in incombustible containers so that the expected fire severity is re- duced to the equivalent of 4 hr or less. (See table 6.) (3) Automatic sprinklers shall be provided in the area where the

excess combustibles occur.

(4) Automatic fire detection shall be provided for the building or

fire area, together with a standpipe and hose system.

•> In type I buildings, unprotected incombustible roof framing and

sheathing may be used to enclose an unusable attic space, provided that

the construction separating the attic from the story below is of incombustible materials with a fire-resistance rating against fire exposure from

below, not less than that specified for floor construction in table 1. Where every part of the roof framing is more than 20 ft above a floor having total combustibles not in excess of 6 lb/ft2 of floor area, roof framing may be unprotected, or an incombustible ceiling thereon of no re- quired fire resistance may be used.

° The required fire resistance shall be determined by the combustible

content on the side of the wall on which it is the higher. In the rase of party walls, and fire-division or fire walls serving as party walls, if subse- quent adjoining construction and occupancy require a higher fire resist- ance than originally incorporated, the fire resistance of such walls shall be increased to meet the new condition.

d The rating shall apply for fire exposure on the side away from the publie space or vertical opening. For fire exposure on the other side the fire- resistance rating shall be not less than } 2 hr.

e No required fire-resistance rating. To be of incombustible material.

Roof Coverings for Type I Construction.—

Buildings of type I construction shall have roof

coverings which meet the requirements prescribed for class 1, 2, or 3 roof covering in

chapter IV.

(6) Type II. Incombustible Construction

That type of construction which has exterior

walls, bearing walls, floor and roof construction,

and other structural members, of incombustible

469723°—42 2 [ 7

materials all assembled to have fire-resistance

ratings as given in the titles of the following

subtypes, and roof coverings as specified hereafter. In type II-A buildings, unprotected incombustible roof framing and sheathing may be

used to enclose an unusable attic space, provided that the construction separating the attic

from the story below is of incombustible materials with a fire-resistance rating against fire exposure from below not less than % hr. Type II-A. Incombustible construction, %

hr. Type II-B. Incombustible construction,

less than % hr. Fire walls and party walls shall be groundsupported and of masonry or other incombustible construction, suitably proportioned as to strength and stability, and shall have fire- resistance ratings not less than those given

below. Connections of building members with

such walls shall be made so that failure of the

floor or roof construction due to fire on one side

will not cause collapse of the wall. The fire resistance of the wall construction shall be not

less than as given in the following table, the

first column of which is based on the total combined weight of combustible contents for all stories plus any in the construction itself.

Table 2.Minimum fire-resistance ratings for fire walls and party walls for type II construction

Minimum fire resistance Total weight of combustibles,

lb/ft 2 of ground area Lower

8 ft 8 to 20 ft above base Over 20 ft above base

Less than 25.. . . hr

v/%

4

hr

2 hr2 25 to 50 2H 2

50 to 75 5 3 2

75 to 100. _ 6 4 2M

100 to 150.. ._ 8 5 3 150 to 200 9 6 3%

200 to 250 — 10 8 4 Over 250 12 10 5

Note.—The wall heights are to be measured from the average interior ground level at the base of the wall.

Thicknesses corresponding to higher fire- resistance ratings than given in the above

table may be required on the score of stability.

Interior walls and partitions enclosing public stairways and other vertical openings and

exits from them in type II-A buildings shall

]
conform with the requirements for fire walls

and party walls from the standpoint of type of construction and shall have a minimum fire- resistance rating of 2 hr. Walls and bottom

and top enclosures for public stairways and

other vertical openings and exits from them for type II-B buildings may be of the same general

type as the interior construction and shall have

a minimum fire-resistance rating of % hr. The

connections to adjoining construction having a lower fire-resistance rating shall be such that

the fire resistance of the enclosure shall be mamtained. Interior partitions enclosing public hallways

shall have fire-resistance ratings of not less than

% hr. Common property-line walls may be of the same general type as the exterior walls, but

shall have fire resistance against exterior fire exposure of not less than 2 hr. Roof Coverings for Type II Construction.—

Buildings of type II construction shall have

roof coverings which meet the requirements

prescribed in chapter IV for class 1, 2, or 3

roof covering.

(c) Type III. Exterior-Protected Construction

That type of construction in which the exterior walls, party walls, and fi're walls are ground-supported and of masonry or other in- combustible construction, suitably proportioned

as to strength and stability, and the interior

framing is partly or wholly of wood or other

similar materials, all assembled to have fire- resistance ratings not less than the minima in- dicated in table 3, and having roof coverings as specified hereafter.

Table 3.Minimum fire-resistance ratings of structural elements for type III construction

Subtype

General fire-resistance ratings in hours

Exterior walls: Distance from common property line or other buildings on the same property: Under 10 ft (including common

propertv-Hne walls) From 10 to 20 ft _ Over 20 ft Fire-resistive partitions

Interior bearing walls Columns, girders, trusses _ Floor construction Roof construction

Interior partitions enclosing: Public hallways

III-B

In type III-A buildings, unprotected roof

framing and sheathing may be used to enclose an unusable attic space, provided that the construction separating the attic from the story

below has a fire-resistance rating against ex- posure from below of not less than % hr. Fire walls and party walls shall have minimum fire-resistance ratings, as given in table 4, based on the total combined weight of combustible contents for all stories plus any in the

construction itself. The fire resistance of the

wall shall be taken as limited by any combustible members projecting into it from the protected area. Floor and roof members shall release as required for Type II construction.

Table 4.Minimum fire-resistance ratings for fire ^valls and party walls of type III buildings

Minimum fire resistance Total weight of combustibles, lb/ft 2 of ground area Lower 8 ft 8 to 20 ft above base Over 20 ft above base

Less than 50 hr

4

hr. 2hr 2

50 to 75 2J4 2H

3

2 75 to 100 5 2

100 to 150 6 .m

in

2M

150 to 200 8 3 200 to 250 10 4 Over 250 12 5

Note.—The wall heights are to be measured from the averge interior ground level at the base of the wall. Walls enclosing public stairways and other

vertical openings and exits from them, for type III-A buildings shall be of the same

general type as fire walls and party walls with

fire-resistance ratings of 2 hr, and the top enclosure shall have a fire-resistance rating of not

less than 1 hr. Walls and bottom and top

enclosures for public stairways and other vertical openings and exits from them, for type

III-B buildings may be of the same general

type as the interior construction and shall have

a minimum fire-resistance rating of % hr. The

connections to adjoining construction having a lower fire-resistance rating shall be such that

the fire resistance of the enclosure will be

maintained.

Interior partitions enclosing public hallways

shall have fire-resistance ratings of not less than

%hr.

Roof Coverings for Type III Construction.—

Buildings of type III construction shall have

roof coverings which meet the requirements

prescribed in chapter IV for class 1, 2, or 3

[8]
roof covering subject to the following limitations:

(1) When the distance of the building from

other buildings or lines on adjacent property on which other buildings may be built is less than 12 ft, class 1 or 2 roof coverings shall be

provided.

(2) When the distance of the building from

other buildings or lines on adjacent property on which other buildings may be built is 12 ft or more, class 1, 2, or 3 roof covering shall be

provided.

(d) Type IV. Wood Construction

That type of construction which has exterior

and bearing walls and floor and roof construction, wholly or partly of wood or other combustible materials, all assembled to have fire- resistance ratings as given in the titles of the

following subtypes and roof coverings as specified hereafter.

In type IV-A buildings, unprotected roof

framing and sheathing may be used to enclose an unusable attic space, provided that the

construction separating the attic from the

story below has a fire-resistance rating against

exposure from below not less than % hr. Type IV-A. Wood construction, % hr. Type IV-B. Wood construction, less than

% hr. The requirements for fire walls and party

walls shall be the same as for type III construction.

Walls and bottom and top enclosures for

public stairways and other vertical openings

and exits from them may be of the same general

type as the interior construction and shall have

a minimum fire-resistance rating of % hr. The

connections to adjoining construction having a lower fire-resistance rating shall be such that

the fire resistance of the enclosure will be

maintained.

Interior partitions enclosing public hallways

shall have fire-resistance ratings of not less than % hr. Roof Coverings for Type IV Construction.—

Buildings of type IV construction shall have

roof coverings which meet the requirements

prescribed in chapter IV for class 1, 2, 3, or 4

roof covering subject to the following limitations:

(1) When the distance of the building from

other buildings or lines on adjacent property on which other buildings may be built is less than 12 ft., class 1, 2, or 3 roof covering

shall be provided.

(2) When the distance of the building from

other buildings or lines on adjacent property on which other buildings may be built is 12 ft. or more, class 1, 2, 3, or 4 roof covering shall be provided.

2. Fire Severity

Fire severity is used herein as a measure of

the intensity and duration of a fire. It is ex- pressed in terms of time of exposure equivalent

to that in the standard furnace test as defined

in American Standards Association Standard

A-2, 1942.

It has been found from burn-out tests per- formed in fireproof structures with various concentrations of combustibles having a calorific value in the range of wood and paper (7,000 to 8,000 Btu/lb) and assembled to represent building occupancies, that the relation between the

amount of combustibles present and the fire severity is approximately as given in table 5. Table 5.

Relation of amount of combustibles to fire severity

Average weight of combustibles, lb/ft* of

floor area

Fire se- verity

Average weight of combustibles, lb/ft* of

floor area

Fire se- verity

5

hr H

3A

1m2

30

Ar

34>S 67H

.... 40

10 50

15 60

20

It is considered sufficiently accurate in computing combustible contents to take wood,

paper, cotton, wool, silk, straw, grain, sugar, and similar organic materials at their actual

weights and to take animal and vegetable oils, fats, and waxes, petroleum products, asphalt,

bitumen, paraffin, pitch, alcohol, and napthalene at twice their actual weights.

When the calorific value of combustibles

differs greatly from that of wood or paper, or where the combustibles are stored in steel or equivalent incombustible containers, a corre- spondingly corrected weight should be used in

[9]
determining expected fire severity from the fore- going table. It is considered sufficiently accurate to use

the percentages, as given in table 6, of the

weights of enclosed combustibles stored in steel containers in estimating the fire severity.

Table 6.

Effective combustible contents of steel containers

Type of container

Part of combustibles in containers

Less than

one-haif

One-half

to three- fourths

More

than

three- fourths

Backed and partitioned shelving Shelving with doors and transfer cases.

.

Filing cabinets and desks. .. Safes and cabinets of 1 hour or more fire- resistance rating .:

Percent

7560

40

0

Percent

755020

0

Percent

7525

10

0

In computing combustible contents, concentrations higher than the average over con- tinuons areas exceeding 500 ft2 or exceeding 25

percent of the floor area between fire separations, whichever is the smaller, shall be considered separately, otherwise the average for the entire area shall apply. With special construction or containers provided as indicated

in table 6 for areas where the concentration is decidedly above the average, it will, in general,

not be necessary to increase the fire resistance

of the construction of the whole building to give protection against such localized hazards.

The data on combustible contents of buildings as contained in chapter III indicate the

range which generally can be expected to be

associated with the various occupancies sur- veyed.

In apartments and residences, even with

combustible floors and other woodwork, the

amount of combustible contents was found to be relatively light, with the average below 10

lb/ft2 of floor area. In areas containing con- centrated furniture storage, the combustible

contents were found to be no moi'e than 14 or 15 lb/ft2

, which includes allowance for a woodfinish floor and wood trim.

In schools the average amount of combustible

contents in classrooms, gymnasiums, and most

laboratories was found to be well within 10

lb/ft2 of floor area. In areas such as storage

rooms, file rooms, paint shops, libraries, stock

rooms, etc., the concentrations varied greatly

with the type of combustibles encountered, but

the areas with high concentrations constituted

only a small percentage of the total. In office buildings the surveys indicate that

the combustible contents in from 80 to 90 per- cent of the building will come within 20 lb/ft2 of floor area. This would include such areas

as offices and reception rooms, even those containing files. In rooms used exclusively for

filing or library purposes, the combustible

contents might run as high as 80 lb/ft2

. The survey of hospitals indicates that the

amount of combustible contents is light, with

the average below 5 lb/ft2 for the greater per- centage of the building. Concentration of

combustibles such as was found in laundries, rooms used for clothes storage, and supplies

did not exceed 20 lb/ft2

. The amount of combustible contents in

warehouses was found to vary considerably,

according to the type of contents stored.

This would indicate that warehouses require

individual study and consideration in relation

to the intended use.

3. Fire-Resistance Ratings

The fire-resistance rating of a structural

element is the length of time that it performs

satisfactorily in the standard furnace test. Unless otherwise indicated, the fire-resistance

ratings specified are for fire exposure on either

side of walls, partitions, and floors and on the

lower side of roof construction. Fire exposure

from below only is assumed for floors or ceilings

under unusable attic spaces, the rating being

based only on absence of collapse or occurrence

of openings allowing free passage of flame and

hot gases through the construction.

Although almost all the data on fire resistance

of floor constructions were obtained with fire exposure from below, a few tests with fire above

the floor indicate a comparatively less severe exposure to the construction for a given fire condition.

CHAPTER II. RESTRICTIONS AND

LIMITATIONS IN THEIR RELATION

TO TYPES OF CONSTRUCTION

The essential conditions which can be provided by design for the safety of life and

property against loss by fire in a building are

[10]
structural resistance to collapse due to fire and to spread of fire, sufficient exit facilities,

and adequate facilities for extinguishment.

The degree of safety in a given case is dependent

on the extent to which the foregoing conditions

are realized.

The major factors which will determine the extent to which the above conditions can be

attained are the hazards due to location,

occupancy, and contents; the height and area

of the buildings; the size of areas not effectively

separated with respect to fire; and the materials and construction of the building. It is usual, therefore, to apply restrictions and

limitations to certain of these factors for the

purpose of obtaining safe conditions to the

degree considered economically possible and

desirable from a public standpoint.

The degree of restrictions and limitations

which have been applied vary considerably, and

the Subcommittee is not here proposing any

definite recommendations but the subject is discussed in general terms. The following general classes of limitations

have been applied to types of buildings differ- entiated by the materials, design, and degree

of fire resistance of their component parts.

Location with respect to fire zones. Permissible height of building.

Permissible spacing from adjacent construction or property lines. Permissible area of building or area within

fire subdivision walls. Permissible materials in building members

and building finish. Required degree of fire resistance of structural members.

Permissible occupancies.

The following discussion will be referenced

to the types of buildings defined in the pre- ceding chapter and is intended to be suggestive

in obtaining a safe application thereof. It will be limited to considerations of safety from fire only. It is recognized that other restrictions

may be applied from the standpoint of general

zoning regulations.

1. Location With Respect to Fire Zones

From the standpoint of fire zoning, cities are generally subdivided into one or two fire

[1

zones and an unrestricted area. In the larger

cities two fire zones may be justified in which new construction is restricted to the Fireproof

type within the inner zone, except that other

types may be permitted if rigidly limited in height and area. In the outer fire zone, besides fireproof buildings, those built with

structural members of incombustible materials

irrespective of the fire resistance thereof, and

those with exterior ground-supported masonry

walls and interior non-fire-resistive construction, are permitted to the limits of height and

area applicable for these types. Outside of

the fire zones all types of construction are permitted to the respective limits of permissible

height and area. In cities subdivided into

only two districts the restrictions outlined

above pertaining to outer fire zone are generally

applied to construction within the fire limits. Restrictions not necessarily directly connected

with permissible types of construction are also applied with respect to roof materials, which

may also be applied outside of fire limits.

This is deemed justified on account of the

possibility of rapid spread of fire in the more

combustible and less fire-resistive construction

prevailing outside of fire limits. The main object of the restrictions is to re- duce to a practical minimum the possibility of

rapid spread of fire. This has been found desirable and necessary not only within congested high-value districts but also in residential districts, based on experience in numerous

conflagrations from the beginning of historic

times up to the present. The provision of exterior self-supporting walls of incombustible

materials is a considerable measure of protection but has not prevented conflagrations where

buildings are near the limits of permissible

heights, closely spaced, and with the larger

amounts of combustible contents, even with

good fire-fighting facilities. For such conditions the Fireproof type has proved, however,

to be very effective.

2. Restrictions Based on Height op

Building

In applying restrictions of this class, some

consideration apparently should be given to the required fire resistance of building members,

permitting buildings having constructions with

U
the higher ratings to be built to relatively

greater heights.

(a) Fireproof Construction

In general no restrictions as to height have

been applied to the Fireproof type of building,

except for occupancies deemed specially hazardous. This may be justified on the basis that

the building should withstand a fire completely

consuming all combustible contents and trim

without collapse of structural members, or that

for the higher amounts of combustible contents,

the fire resistance incorporated in the building,

in combina tion with its fire-extinguishing equipments and the public fire protection, is deemed

adequate to prevent such collapse.

Structural protection against fire exposure

from the outside also is assumed and can be

provided without difficulty, since the lack of

confinement for the products of combustion will prevent high exposure temperatures over long

periods. While exposure from radiation may

be intense, this will be limited in time to the

most active stage of the fire. The resistance

against exterior fire exposure is usually limited

by the openings in fire-exposed walls. Although

opening protectives are required for major

buildings where the openings are within 30 to 50 ft from exposing construction or openings,

it is recognized that under severe fire conditions

fires can be communicated through unprotected

openings at greater distances. The opening

protectives generally required do assist materially in preventing communication of fire where large buildings are closely spaced.

Greater spacings will decrease materially the

degree of fire fighting from within and without

required to prevent ingress of fire. Another reason for the very moderate re- strictions on height applied to the Fireproof

building is its inherent advantages in point of

limiting the spread of fire and smoke, resulting

in greater safety to occupants and less difficulty

in extinguishing fire. With incombustible floor construction of the required degree of fire re- sistance and enclosed vertical openings, the fire will be prevented from spreading from floor to

floor through interior channels and the travel

of smoke will be greatly restricted. For other

than the lighter amounts of combustible contents, fire may be communicated from floor to

floor through unprotected exterior wall openings, but this can be prevented with moderate

fire-fighting effort. The building is relatively

safe for entry by fire-fighting forces, and fire- fighting equipment can be provided within the

building with the outlets and connections so located or protected as to give good assurance

of its availability in case of fire. These properties of the construction also

enable conditions having a bearing on the

safety of occupants to be evaluated with a good

degree of reliability. While with non-fireresistive construction it is generally considered

necessary to provide for exit of all occupants

from the building or fire-division thereof within a given time, the greater barrier to spread of

fire and smoke offered by the floors and other

subdividing constructions in Fireproof buildings

makes it necessary to provide means for immediate exit only from the area directly in- volved. This greatly reduces the required

capacity of stairs which otherwise would be

prohibitive for high buildings.

With occupancies involving large amounts of

flammable liquids or other readily combustible

materials, the building construction affords less protection and the application of height restric- tions is justified irrespective of the type of construction. Fires in such contents progress

rapidly, with production of large volumes of smoke and gases that may be forced into protected exit ways, making them untenable,

hence the need of facilities for prompt egress of occupants. Fire-fighting operations are more

difficult and hazardous than for fires in ordinary combustibles, and explosions, even if not

violent, may endanger the stability of the

building. Without special provisions, no building presents any considerable resistance to explosive effects, although the Fireproof building has generally less inherent weakness in this respect than those of other types, and with

proper choice of materials and design and

provision of suitable vents, its resistance can be

greatly increased.

(b) Incombustible Construction

While the Fireproof building must have sufficient structural protection, and other associated facilities, if needed, to assure freedom

from collapse due to fire, such restriction does

[12]
not apply to those of the Incombustible type.

Hence, provision for prompt egress of occupants

must be made. Also, the possibility of con- ducting fire-fighting operations from within the

building is not assured unless the fire is of low or moderate severity or is controlled in its early

stage. The general limit of height to which an

effective fire department hose stream can be

directed from the ground to fight fires in a

building is near 50 ft. This can be increased some 30 ft by mounting the hose on the first section of the aerial ladder. Any added range

would have to be obtained with hose towers, the

limit of height of which is near 100 ft. At this height the water pressure available from the

pumpers and safely carried by the hose lines,

becomes a limiting factor. These considerations will limit the height to which buildings

other than those of the Fireproof type can be

safely built. Buildings of the Incombustible type with

structural connections or adequate ties between

the exterior and interior framing would present

little hazard due to possibility of collapse onto

adjacent property when failure occurs, assuming

that the ratio of least lateral dimension to height of building is not excessive, since there

would be a tendency for the framing to be pulled

inwards. For self-supporting exterior walls,

such as of masonry, on which interior construction is supported and secured with only the

usual forms of ties or anchorage, the conditions

from the standpoint of hazard to adjacent

property would be substantially the same as

for the Exterior-Protected building outlined

below.

The incombustible floor and roof constructions in collapsing tend to blanket the fire and

prevent hazard to the surroundings from flying

brands. Although the resistance of unprotected members to collapse due to fire is comparable with what obtains for unprotected

wood-joist construction, fire and smoke are better confined. The absence of any consequential amount of combustible materials in the structural members and accordingly, in the

materials forming the boundaries of any concealed spaces formed by them, further removes

conditions inducive to rapid spread of fire. It also would be expected that irrespective of

any restrictions applied, the amount of combustible insulation, finish, and trim would be

less than for wood interior construction. These

all have a bearing on the safety of occupants

and the ease with which fires can be controlled

in then early stages.

As protected to obtain given fire-resistance

ratings, Incombustible construction would be

the equivalent in this respect to similarly protected Wood construction except that where

failure under load or other structural collapse

is not involved, the incombustible constructions

would continue to present a barrier to the spread

of fire and smoke for a longer period after limiting technical end points, such as temperature

rise on the unexposed side, have been reached.

(c) Exterior-Protected Construction

In an effort to prevent the conflagrations that

repeatedly have devastated centers of population, buildings in closely built-up areas have

been required to have exterior and party walls

of masonry. These walls are required to be

self-supporting in the sense that they are carried

directly on their foundations, and as supported

laterally by the floor and roof constructions, are stable under the normal lateral forces to which they are subjected. Such stability also can be regarded as maintained under exterior

fire exposure, and protection to interior construction and building contents can be given

substantially as for the other building types

discussed above. To achieve such protection

in the same degree, care must be taken in the

details employed at the eaves, cornices, and

projecting dormers or towers, to eliminate

possibility of ready ingress of fire through open

spaces or spaces sheathed or filled only with

combustible materials. The ends of combustible members projecting into the walls must

have sufficient thickness of protective material

to the outside to prevent ignition from the

exposing fire, a condition generally attained

without difficulty in exterior walls but which

may be a limiting factor in the protection given

by party and fire walls. The effect of unprotected and protected wall openings on the

protection afforded by the wall construction is the same as for the other building types.

When the interior construction of ExteriorProtected buildings collapses because of fire, the stability of the exterior walls of multistory

[13]
buildings is largely destroyed. The heat from

the fire causing expansion of the inner face

will deflect the top of the wall outward thus

increasing its instability, and collapse to within

a storj'-height or two from the ground is to be

expected in a fire consuming the interior construction and contents. This instability of the

walls under fire exposure from within the building introduces an element of hazard to adjacent

property and to firemen, for buildings of any

considerable height. The protection given

adjacent construction is limited by this condition and even heavy built-up or metal roof

coverings exert little blanketing effect in a

severe fire, since they are consumed or dis- integrated into then component units. This,

as well as the practical heights to which fire- department hose streams can be applied, is a

consideration that limits the height of buildings of this type.

From the standpoint of safety to occupants,

facilities for egress from the building or fire subdivision thereof within a limited time,

need to be provided. Protected stair shafts

increase the allowable time for egress and also serve as a protection for fire-fighting operations.

It is apparent, however, that the height of the

building must be restricted for these reasons,

as well as on the score of hazard to adjacent

construction. Even with its limitations this building type has served very effectively in preventing ready communication of fire from

building to building. With a moderate degree

of public protection, fires in buildings presenting the lighter degrees of hazard, such as those

of the residential type, can be controlled without

much likelihood of spread to adjacent construction. No separate classification is made for the

heavy timber or mill construction type since

its fire resistance in the lower range as unprotected is not higher than the %-hr limit designated for the present type and attainable with

protected interior wood constructions framed

with lighter members.

(d) Wood Construction

The essential difference between this type of

construction and that designated as ExteriorProtected is in the exterior framing and facing.

The latter may vary from wood or metal siding

to masonry veneer, and the sheathing against

which they are placed may be of combustible or largely of incombustible materials. As for the

preceding type, there may be also a wide range

in combustibility and fire resistance of the

interior construction and finish, greatly affect- ing the safety of occupants and the ease with

which fires can be controlled in their early

stages or prevented from spreading to adjacent

construction.

Although the higher range in exterior protection attainable may approximate that with

Exterior-Protected construction, masonry ve- neer is less stable than solid masonry walls and

with combustible exterior finish the building is more vulnerable to exterior fire exposure.

These considerations justify further restrictions

in height for this type, although the hazard

to occupants with the same type of interior

framing and finish may not be much different

from that obtaining for the Exterior-Protected

type.

3. Restrictions on Locations with Respect

to Common Property Lines or Adjacent

Buildings

The objects of these restrictions apparently

are to decrease the possibility of rapid spread

of fire and afford a space between buildings for

fire-fighting operations. It does not appear to have been practical by such restrictions to achieve much assurance that the walls of a

building will not collapse on adjacent buildings

or property when the building or its interior

construction is destroyed by fire. The restrictions that have been applied refer

mainly to Wood construction, walls of which

have been required by building codes or other

restrictions to be located from 1% to 10 ft from

the common property line or from 2% to 20 ft from the adjacent building, the most usual

range being 3 to 5 ft for the former and 6 to 10

ft for the latter. In many codes the restriction

is applied to the Avail concerned rather than to the whole building, the wall located within a given distance from the common property line or adjacent building being required to have a

specified fire-resistance rating. It is questionable whether requirements thus phrased achieve.

[14]
the desired object, since the matters of interest are quite apparently the material in the wall

and its stability, which are not necessarily

directly determined by its fire-resistance rating.

Very few restrictions have been applied in

this respect to buildings of the Fireproof or Exterior-Protected type where the walls con- cerned are without openings. Where there are openings, or for places of public assembly, a minimum distance to the common property

line or between buildings has been required, for the latter to afford a passage for egress. From the standpoint of the hazards with

which restrictions of this class are concerned,

it is apparent that buildings of the Fireproof

type give the greatest protection. The next in

order would be those of the Incombustible or the Exterior-Protected type, depending on conditions. Where there is a space between the

buildings, those of the Incombustible type with

members having %-hr or greater fire-resistance

rating may present the lesser hazard. This

concerns degree of hazard to adjacent property

from collapse of building and building walls and

the blanketing effect on the fire of floor and

roof constructions both before and after col- lapse. Where the building extends to the

common property line, there are advantages in

favor of the Exterior-Protected type over the

Incombustible type unless similarly protected,

particidarly if the buildings where they adjoin

are of approximately the same height and

depth. Whether the adjoining walls are built as party walls or as individual common-propertj^-line walls, a fair assurance of stability of

the party wall or adjacent common-propertyline wall is had when the construction on one

side or the other collapses because of fire. This assumes that the floor and roof constructions on

both sides are tied into the wall in such manner

as to give the required degree of support to the

wall when exposed to fire from the outside, but

in the case of party walls, collapsing members

are released to an extent that will enable the

wall to retain its stability and fire resistance. It appears that walls of buildings of the

Incombustible and Wood construction types

when built to the common property line should

conform with the requirements for party and

common-property-line walls of buildings of the

Exterior-Protected type, from the standpoint

of both stability and fire resistance. Although

the stability of walls of buildings of the Fireproof type is assumed established at least for the applicable fire-resistance rating, their fire- resistance rating as party walls should at least correspond to the expected fire severity for the

adjacent area in the original building. If subsequent construction on the other side

introduces a higher fire severity, the fire resistance of the wall should be correspondingly

increased.

For common-property-line walls a uniform

requirement of 2 hr is applied on the assumption

that a wall subsequently built in contact with

it will have equal fire resistance. If the two

walls so constructed do not in combination meet

the requirements for a party wall in the given

location, the fire resistance thereof should be

increased or some of the other provisions under

table 1, footnote (a) applied. The fire resist- ance of exterior walls other than commonproperty-line walls is based on ability to support

load and retain stability under fire exposure

and on temperature rise only as it concerns fire exposure from the outside.

The practice of permitting unmodified walls

of the designs typical for Incombustible and

Wood construction type buildings as party and

common-property-line walls does not appear

justified, even where the wall and construction on each side have up to 1-hr fire-resistance

ratings. For occupancies involving the lower

amounts of combustible contents in buildings

of the Incombustible type, no great hazard may

be involved but it may be increased with

changes in occupancy. Wood construction,

irrespective of its fire resistance, will eventually

collapse in any fire involving a considerable

portion of the construction or building contents, assuming no fire extinguishment. Even

with good fire fighting, fire and smoke are likely to be communicated through concealed spaces

in the construction, the firestopping of which

cannot be fully assured. Some improvement

is obtainable with double construction at the

common property line, with an intervening

continuous fire barrier in the form of incombustible fire-resistive blankets or similar separations, designed to remain in place when the

construction on either side collapses. However, in general, party and common-property469723°-—42 3 [15]
line walls conforming with the requirements for Exterior-Protected construction constitute more

effective barriers.

Requirements based on distance from the

common property line can be made unduly

restrictive unless tempered with respect to

size of building. Thus, a certain separation

deemed proper for buildings several stories

high cannot with justification be applied to small one-stoiy buildings, such as private

garages. Such buildings, even if of Wood

construction, particularly with incombustible

facings, can safely be permitted closer to the

common property line or similar adjacent

building. Assuming some separation, incombustible unprotected buildings of such size present less hazard from this standpoint than

those with masonry walls and combustible roof

construction.

4. Restrictions Based on Area of Building

The objects of regulations of this type are to

restrict the spread of fire, obviate conditions

unduly hazardous to occupants from the standpoint of egress, and to provide access for fire- fighting purposes. The practice of permitting

greater areas for buildings fronting on two or more streets than for those with a single frontage may be justified on the score of access for

fire-fighting equipment, although the additions

generally permitted on this score in building

codes appear relatively large. Under some

regulations, areas having a long street frontage

are permitted to be larger than those having a

greater ratio of depth to frontage, presumably

for the same reason. Buildings or groups of

buildings located some distance back of any

public street front but having improved roads

or streets leading up to them equal to public

streets, will in general give accessibility to fire apparatus equivalent to frontage on two or more public streets. Increases in permissible areas of 50 to over

100 percent are generally allowed if automatic

fire-extinguishing equipment is installed. Some

regulations restrict such permissible increases

to business buildings, garages, and other commercial types. In a few regulations, low buildings are permitted larger areas than those that can be built to the limit of permissible height,

although there has been no general systematic

application of this principle. For non-fireresistive construction, the hazard from spread

of fire appears to be fully as much a function

of the volume of the building or fire subdivision

thereof as of the ground area occupied.

In applying area restrictions, some allowance

might be made for the required fire resistance

of building members by allowing buildings with

members of the higher ratings to have larger

undivided areas.

(a) Fireproof Construction

Buildings of this type are generally unrestricted as to area, with the exception of those

considered specially hazardous, such as public

garages. It is a question whether a number of

other occupancies involving large amounts of

combustible materials or readily flammable

materials do not present as great or greater

hazard. The inherent protection given by

Fireproof construction is recognized where light or moderate contents of ordinary combustible

materials are involved, but for higher concentration or more readily combustible materials

the retarding effect of the construction is of

less import. This construction has the advantage that structural fire subvidision can be

made with good assurance that the subdividing

construction will fully serve its purpose, assuming its fire-resistance rating is adequate for the

conditions presented. The full value of fire- proof construction can be attained only where

such subdivision is logically applied. However,

many occupancies require such large areas from

the standpoint of operating conditions, of the

order of several hundred thousand square feet,

that any restrictions applied above such limits

would have little meaning. Examples are

certain types of metal working and assembly

plants. If the contents are largely incombustible and there is a minimum of combustible

building finish and trim, such large areas would

present no greater hazard than smaller spaces

with higher combustible content. For others,

the safety to property and under some conditions, to occupants, can be appreciably improved by judicious subdivision. The safety

from the standpoint of emergency egress in

establishments such as retail stores would be

greatly increased with at least one subdividing

construction for large areas.

[16]
Assuming an occupancy that can be safely

permitted without restriction as to area or within a given permissible area, it appears illogi- cal to stipulate in effect further subdivision of

this area by requiring ordinary room partitions

to have given fire-resistance ratings. This

applies especially where the whole area is covered by the same occupancy or tenancy.

Such partitions, if wholly or largely of incombustible materials, will retard the progress of

fire to some extent, but there appears no justification for requiring a fire-resistance rating.

It is recognized that partitions serving as protection for shafts and egress corridors should

be required to have some degree of fire resistance.

For egress corridors this need be no greater

than one-half to one hour. Considering that

shafts may be used by fire-fighting forces, a

greater protection for them is justified. The

actual fire exposure on the shaft side of protected enclosures is very light, justifying in

general a lower limit of fire resistance for the

enclosing construction exposed from the inside

than from the other. The same applies also to some extent for corridor partitions.

(6) Incombustible Construction

With this as with other buildings not of the

Fireproof type, collapse in whole or part may

occur from fire exposure and hence the need of providing protected ways of egress for occupants. This may be a limiting consideration

from the standpoint of permissible area, since

the distance to any exit must be limited and

vertical exit ways are located preferably on or near exterior walls. This type of building affords more favorable

conditions than those of combustible interior

construction in restricting the spread of fire and for fire-fighting operations in case collapse

does not occur, or before it occurs in fires taxing

the building constructions beyond their ulti- mate fire resistance. Beyond this stage, al- though the fire may be subdued by the collapsed

incombustible constructions, fire fighting is made more difficult, since hose streams are diverted by them and fire spread to portions

that have not collapsed and are within the same fire area can with difficulty be prevented.

Such buildings if of one story are generally

unrestricted as to area and height even if

structurally unprotected. This may be jusli- fied as far as light-hazard occupancies are concerned, but for the larger amounts and more

hazardous types of contents, restrictions apparently should be applied, considering what

is done in the case of other buildings not of the

Fireproof type.

(c) Exterior-Protected Construction

The same considerations from the standpoint

of area limitations apply in general as for buildings of the Incombustible type. The interior

construction will afford somewhat greater

opportunity for rapid spread of fire and on

this account the individual areas might logically

be restricted to a little greater extent than for buildings of the Incombustible type. Unless

the floors are of heavy laminated wood, or of lighter construction having fire-resistive plaster or other equally effective soffit protection, the

vertical spread of fire will be less restricted.

To obtain the protection premised with the

exterior wall construction, it appears that all walls forming a boundary of the building, in- cluding walls bordering on interior courts,

should be constructed the same as the exterior

walls. The practice of permitting interior- court walls to be of wood frame appears inconsistent, even if protected to give 1-hr fire resistance, considering the decreased protection

from fires in adjacent wings. Further, court

walls thus constructed would not qualify as boundaries for fire subdivisions based on area.

(d) Wood Construction

Although it may appear that there is no

decided difference between buildings of this

type and Exterior-Protected buildings in fea- tures governing area restrictions, actually as constructed a considerable degree of distinction

is discernible. The undivided areas for the

latter type generally will be distributed in wings separated by courts or light wells, the

required incombustible self-supporting walls of

which will retard appreciably the spread of

fire, as compared with combustible construction,

and spread to adjacent construction is rela- tively more readily prevented with self-supporting exterior walls. However, considering that

buildings of the Wood construction type are

also more restricted as to height, justification

[171
for the large differences in permissible area

often applied as between the two types, is not

readily apparent. In some regulations the

permissible size of buildings of this type is conditioned on distance from the nearest com- mon property line.

5. Restrictions on Type op Materials in

Building Members and Building Finish

As far as the type of materials in structural

portions of buildings is concerned, this is largely

defined for the different types of construction.

Thus, in buildings of the Fireproof and Incombustible types as defined herein, all structural

members are required to be of incombustible

materials irrespective of the degree of fire resistance. For the Exterior-Protected type

the requirement for incombustible materials is limited to the exterior wall construction and

certain subdividing constructions such as party

walls, fire walls, and shaft enclosures. For

Wood construction, there would be no requirements as to materials except for subdividing

constructions, although it is implied that no

materials more readily flammable than wood

can be used at least in structural members.

Accordingly, from this standpoint, the materials would be restricted in their use by the

requirements pertaining to the different types

of construction.

As concerns materials in building finish and

trim, restrictions based thereon have been

applied, although not to the extent that might

be justified. Thus, according to the New York

Building Code, no untreated combustible finish

floors or trim can be used in buildings over 150

ft high. Otherwise, in type I buildings generally, wood finish floors and the usual amount of wood trim can be used. This, however, should

not be taken as implying that such buildings can

be finished over the whole or the larger portions

of the interior surfaces with combustible materials. This would introduce a much greater

hazard than their use in doors, baseboards,

moulding, and similar trim which does not

constitute a large percentage of the wall area and does not afford ready opportunity for the

spread of fire. As a concession in this direction, some codes permit interior partitions of wood, or wood and glass, in areas not exceeding 5,000 ft2

. This will in general include subdividing partitions only, corridor partitions being otherwise

required to be of incombustible materials.

It is apparent that the application of combustible trim over any considerable portion of the

interior surfaces of buildings greatly increases

the fire hazard irrespective of the degree of fire resistance of building members. Such trim will accelerate the spread of fires started in combustible contents that otherwise might be easily

restricted to the room or area in which they

originate. After air temperatures have been

built up to or near the ignition temperature,

rapid spread of fire can take place on combustible finishes and veneer of no greater thick- ness than %2 in. The prohibition of readily combustible curtains and other decorations in places

of public assembly is fully justified on the basis

of experience. Many fires disastrous from the

standpoint of life loss have occurred in them

even where the building itself suffered little damage.

Although for the non-fire-resistive building

types, building codes apply few restrictions in

point of materials for interior finish, it is con- ceded that a wide range in safety to life as well as

to property is presented by the different materials used for the purpose. In the evolution of modern building construction a decided improvement in this respect was achieved by the

substitution of plaster for wood finish. The

more recent introduction of materials in sheet

form, as readily or more readily combustible

than wood, has modified this trend.

Of materials used on the exterior of buildings,

those used for roof covering are generally the

subject of restrictions from the standpoint of

spacing of buildings, type of construction, and

occasionally occupancy. This has been done

with the object of limiting the community fire hazard. Also, such restrictions may be re- quired in order that the exterior construction

may achieve a given resistance against fire exposure from the outside. The wall finishes applied to wood construction present a considerable range in this respect, including as they

do masonry veneer, stucco, metal, or wood

finish. Little recognition has been given in building codes to the difference in the fire hazard thus presented except for requirements

in relation to spacing from the lot line or adja- cent buildings.

[18]
6. Restrictions Based on Degree of Fire

Resistance of Structural Members

Restrictions on the above score have been

applied mainly in the different uses permitted

for the different types of building constructions.

Whereas buildings of the Fireproof type can be

constructed to have a high degree of fire resist- ance, that of the other types is necessarily

limited from the standpoint of practicability

with the types of materials available. In some

codes, buildings essentially of the Fireproof

type are placed ha two classes, a higher degree of

fire resistance being required for one than for the

other. Those to which the lower requirements

pertain are however limited as to height and

area, whereas few restrictions in these respects

are applied for the more fire-resistive type. In

the code developed by the Pacific Coast Building Officials Conference, the dividing line in

point of permissible height is placed at 85 ft. and in other codes recommended requirements

have nearly the same limitations.

Assuming that Fireproof buildings are designed to withstand a complete biirning-out of

contents and combustible trim without collapse,

there should in effect be no limitations imposed on the score of degree of fire resistance other

than in its relation to the expected fire severity

for the given building. However, considering

that public control over the amount of combustible contents in a given building can be

exercised only within limits even where the

occupancy is subject to control, and further,

that the degree of fire resistance of building

members cannot be achieved within very

definite limits, there is justification for applying more rigid restrictions to buildings with the

lower degree of fire resistance, particularly from

the standpoint of height.

For buildings generally associated with the

lower range in combustible contents, such as

residential and office buildings, it does not

appear justifiable even from this standpoint to apply an unduly large factor of safety. Where

the expected fire severity is in the range % to iy2 hr, a 2-hr requirement for high buildings

should give good assurance of stability under

fire conditions. It is noted that fire-resistance

ratings are based on the performance of members near the lower range in size. For the

larger size of members used in all but the upper

stories of such high buildings, there would be

considerable increase in fire resistance above the

nominal ratings for the same kind and thickness

of protecting materials. Also, the structural

continuity inherent in the type of construction

increases the margin of safety on stability

above that indicated in test furnaces for comparable fire exposure and loading of segregated

columns, beams, and floor and wall assemblies.

For buddings other than those of the Fireproof type it is apparent that even in the range

of fire resistance up to % hr a decided difference

in hazard to life and property is presented that

would justify recognition in height and area

limitations. Present restrictions are based

largely on the use of the ordinary type of in- terior constructions having fire resistance of

less than % hr.

7. Restrictions Based on Occupancy

The fire hazard of an occupancy can be

evaluated in terms of the number and concentration of occupants, whether or not such occu- pants are able-bodied and free or confined or

restrained, and the degree of combustibility and

amount of combustible building contents asso- ciated with the occupancy. The larger places

of public assembly have been restricted to buildings of the Fireproof type according to some regulations, although distance of the main

assembly floor above ground, facilities for exit,

and interior finish apparently would be at least equally important. Where the occupants are restrained as in prisons, reformatories, and

insane asylums, rigid restrictions on construction and interior finish of buildings appear

justified, considering that disastrous fires from

the standpoint of loss of life have occurred even

in one-stoiy buildings where these conditions were unfavorable. Similar, although less rigid

restrictions with respect to permissible type of

construction, have been applied for hospitals

and schools. Many codes that permit several

types of construction for such occupancies

apply different restrictions to the respective,

types in point of height and area. It is apparent

that buildings housing hazardous occupancies

should be restricted to some extent in point of permissible type of construction, although

[19]
other considerations—such as spacing from

other buildings, height and area of building, and

the provision of adequate exits—may be more

important.

The largest loss of life in burning buildings occurs in those housing occupancies of the

residential type, including hotels, apartment

buildings, and other types of multifamily

dwellings as well as private dwellings.

Although associated with the lower range in

combustible contents and concentration of occupants, there is apparently a considerable

hazard at night when the occupants are asleep.

The limitation in point of height for residential

buildings of other than the Fireproof type has

been variously placed at 3 to 6 or 7 stories. Considering that the application of firestopping

to prevent communication of fire through the

concealed spaces in wood framing cannot be

assured, it appears that a reasonable degree of safety in the higher buildings having such

framing is difficult to obtain. The increased

safety with incombustible floor and other subdividing interior construction has been abundantly indicated by the fire record. Also, there

would be less objection to more rigid requirements in this respect if the required fire resis- tance of buildings recognized as fully fireproof

for the purpose were proportioned with respect

to the relatively low fire severity to be expected

from the occupancy.

CHAPTEK III. SURVEY OF COMBUSTIBLE CONTENTS OF BUILDINGS

As an assistance in applying fire-resistance

requirements, surveys were made under the

auspices of the Central Housing Committee of combustible contents associated with repre- sentative types of occupancies or buildings.

In tests that have been conducted to obtain

information on the intensity and duration of

fires in buildings, it has been indicated that

there is a fairly definite relation between the

amount of combustible contents and the result- ing fire severity. This is applicable for the

buildings having the main structural elements

of incombustible materials of fire resistance

sufficient to preserve their integrity in a fire consuming all the combustible contents. Considering the wide range in weight of the

combustible contents to be found in buildings,

it appears logical to proportion the fire resist- ance of structural members with reference

to the severity of fires that can occur within

them.

In the surveys (see tables 7 to 17) the weights were obtained by weighing furniture and other

contents in sufficient number to enable the total weight within an area to be computed. The

weight of the combustible flooring and trim was determined from the thickness and area, which method was also applied for fixed furni- ture and other contents that could not be

weighed.

For a given room the doors, windows, frames,

and trim are included in general at one-half

then- total weight. The combustible contents

and area of closets have been averaged with

those of the room served by the closet. The

total weight of the combustible contents of

metal lockers, filing cabinets, etc., is included.

No weight is included for possible escaping

illuminating gas. In school surveys the contents of the storage rooms represent the maximum weight ordinarily stored therein. Pupils'

desks are assumed to be empty. The weight

of pupils' wearing apparel is not included.

In small areas, such as closets in residential

building's, concentrations considerably higher

than the average were found, this being reflected to some extent in the average for the rooms

which they served. A summary of combustible

contents of such closets is given in table 8. Considering the small areas and the fact that

closet doors if not open are generally of type

that will burn through inside of 10 minutes,

it is apparent that then- contents should

be averaged with that of the adjoining room or hall. It is seen that the greater portion of the combustibles is in trim, lining, and

shelving.

These surveys indicate the range in combustibles associated with the occupancies covered. Thus, for residential buildings, the

weight of combustible contents is uniformly

light. The same applies for school and office buildings except for areas used for filing or

storage, which generally constitute only a small percentage of the total area. For warehouses the range is wider, although the concentration has some relation to the type of

[20]
Table 7.

Summary data for apartments and residences Table 7.

Summary data for apartments and resi- dences—Continued

Survey No.Floor

area

Combustible contents

Movable property

Floor

Exposed wood- work Tota

other than

floor

Entire apartment or residence P lb/ft2 lb/ft' Ib/fl- lb/ft' A-l... 695 3.1 3 3.6 9.7 A-2 670.5 2.5 3 2.8 8.2 A-3 544 2.4 2.7 3.4 8.5 A-4 604. 5 2.7 3 2.6 8.2 A-6 : 519 3.4 3 2.9 9.3 A-7 _ 647 4.0 3 2.7 9.7 A-8.-- 431 3.4 3 3.6 10 A-9 514 3.5 3. 2.9 9.4 A-10 734 3.7 1.9 2.9 8.5 A-ll 734 2.9 1.9 2.8 7.6 A-12 748 4.9 0 2.7 7.6 A-13... 529 4.6 3 1.5 9.1 A-17 796 3.1 3 2. 2 8.3 Average 3.4 2.6 2.8 8.8

Basement

A-l 783 0.8 0.0 0.2 1.0

Bathroom

A-l 58 1.2 3.0 1.0 5.2 A-2 60 0.4 2.2 7.4 10.0 A-3 _. 35 .1 0.0 1.9 2.0 A-6 __ 42 1.2 . 5 7.1 8.8 A-7- 35 0.5 3.0 3.0 6.5 A-8 35 .8 3.0 3.0 6.8 A-9 35 1.

1

3.0 3.0 7.

1

A-10 42 1.5 3.0 2.8 7.3 A-ll _.. 42 1.5 3.0 2.8 7.3 A-17 47 1.6 3.0 4.5 9.1 Averace 1.0 3.7 7.0

Bedroom and bedroom closets combined

A-l_-_ A-l___

A-2°._ A-3_._

A-6_..

A-7-._ A-7... A-84 .- A-9.-_

A-10, - A-104 _ A-U_-

A-ll»_ A-12._

A-13»_

A-13"- A-17.-

A-17..

Average.

110 3.7 3.0 3.1 9.8

136 5.4 3.0 4.6 13.0

86 3.9 3.0 1.9 8.8

188 4.1 3.0 2.3 9.4

133 7.3 3.0 2.5 12.8

128 6.5 3.0 2.2 11.7

145 6.7 3.0 2.0 11.7

133 5.0 3.0 3.2 11.2

138 6.2 3.0 4.0 13.2 112 4.8 3.0 2.6 10.4

161 3.8 3.0 3.1 9.9

112 6.6 3.0 2.6 12. 2

161 4.3 3.0 2.2 9.5

154 3.8 0.0 3.0 6.8

144 4.4 3.0 1.6 9.0 80 7.2 3.0 1.5 11.7

126 4.2 3.0 1.8 9.0

126 2.5 3.0 1.8 7.3

5.0 2. 6 10.4

Dining room

A-2-. — 132 2.9 3.0 1.9 7.8 A-4 137.5 3.6 3.0 0.7 7.3 A-12 224 3.0 0.0 3.5 6.5 Average 3.2 2.0 7.2

A-l.- A-l..

A-2-.

A-3_.

A-4__

A-6__ A-7..

A-8..

A-9..

A-10. A-ll.

A-17.

Average.

Combustible contents

Survey No.

Floor

area Movable property

Floor

Exposed wood- work

other than

floor

Total

Hallway

ft 2 21

1186

25

81526742

2827

27

20

lb/ft' 2.6

1.0

2.1

1.0 5.4 0.0

.0

.0

.0.0

.0

.0

1.0

lb/ft' 3.0

3.0 3.0

3.0

3.0

3.0

3.0

3.0

3.0

3.0

3.0

3.0

lb/ft' 6.5

9.7

2.4

7.4 0.6

6.8 5.8

8.1 5.5

7.7

7.7 9.5

Kitchen

Library

Storeroom (apartment house)

A-5__ A-5..

A-14. A-15.

A-16.

A-17. Average.

264

301 432

1,221

1, 446

6.2

2.4

8.8

8.0

10.0

2.8

6.4

0.0

.0

.0

.0

.0

3.0

1 No closets.

1 Two closets.

6.5

A-l 109 1.6 3.0 6.1 10.7 A-2 152 0.7 3.0 2.4 6.1 A-3 47.5 .2 0.5 4.0 4.7 A-4 _ 148.5 .7 3.0 4.2 7.9 A-6._ 96 1.0 3.0 2.6 6.6 A-7 90 2.1 3.0 3.2 8.3 A-9 137 0.5 3.0 3.0 6.5 A-10 171 .5 1.0 1.4 2.9 A-ll 171 1.8 1.0 1.7 4.5 A-13 103 3.8 3.0 1.4 8.2 A-17 87 0.7 3.0 4.5 8.2 Average 1.2 3.1 6.8

A-12._ - 146 10.6 2.4 13.0

Living room

A-l 250 3.3 3.0 1.9 8.2 A-2... 132 4.8 3.0 2.6 10.4 A-3 233 3.3 3.0 2.0 8.3 A-4 237.5 4.3 3.0 1.3 8.6 A-6.. _ _.- 175 3.5 3.0 0.6 7.

1

A-7 167 3.0 3.0 .7 6.7 A-8 213 3.6 3.0 1.9 8.5 A-9 167 4.6 3.0 1.1 8.7 A-10 217 6.8 0.0 3.5 10.3 A-ll.-- 217 1.4 .9 3.4 5.7 A-12 224 4.4 .0 2.1 6.5 A-13 202.5 4.3 3.0 1.6 8.9 A-17 283 3.9 3.0 0.9 7.8 Average . 3.9 1.8 8.1

0.0

.0.2

.0

.0

1.8

0.3

Vestibule

A-2 22.5 2.2 3.0 4.4 9.6

[21]
materials that are stored. It is probable that

similar conditions obtain for stores, manufacturing establishments, and other commercial

occupancies.

In the summary tables are given the areas, and in some cases the percentages of the total area, over which a given concentration or range

in combustibles was found. The concentration

is expressed in pounds per square foot of floor area, assumed uniformly distributed, and applicable for materials, such as wood and paper, that

have calorific values in the general range 7,000

to 8,000 Btu/lb for the dry material. Where

combustibles differing markedly in calorific value from the above were present, their weights were modified to give the equivalent weight

of a material having a calorific value of 8,000

Btu/lb.

Table 8.

Summary for closets in residential buildings

Closets Average

floor area

Movable property

Floor Other wood- wort

Total

Type Number Average Maxi- mum

Mini- mum

ff Iblff Iblff Iblff Ib/ff Ib/ff Iblff Clothes 28 8. 75 5.

1

2.7 11.6 19.4 30.2 10.2 Linen 9 4. 77 11.7 3.0 21.4 36.1 49.3 26.2 Kitchen 1 5. 00 4.0 3.0 23.2 39.2

Table 9.

Summary data for offices

Combustible contents

Survey Nb;

Floor

area Movable property

Floor

Exposed

wood- work

other than

floor

Total

Office (only)

Iblff 0-17 ff

285

122

Ib/ff 3.8 4.9Ib/ff 3.3

0

Iblff1.7 2.1Iblff8.8 0-28_.__ 7 Average _ . 4.4 1.9 7.9

Office and reception room

0-6 _ _ 0-21 Average

289 2922.6

2.4

03.31.7

3.

1

4.3

8.8

2.5 2. 4 6.6

Table 9.

Summary data for offices—Continued

Combustible contents

Survey No.

Floor

area Movable property

Floor

Exposed

wood- work

other than

floor

Total

Office and light files

0-1 ff Ib/ff Iblff Iblff Iblff 656 10.7 0.0 1.2 11.9 0-2 336 8.6 .0 2.1 10.7 0-3 336 9.9 .0 2.7 12.6 0-4 1,321 3.8 .0 2.9 6.7

0-5 467 10.2 3.3 2.2 15.7 0-7 739. 5 5.7 .0 1.8 7.5

0-8 739. 5 8.1 .0 0.8 8.9 0-10 742. 5 2.9 .0 .9 3.8

0-11 775. 5 8 .0 .9 8.9 0-13 448 6.4 3.3 1.4 11.

1

0-15 323 4.6 3.3 1.5 9.4 0-16 170 11.5 3.3 1.9 16.7 0-18 388 3.9 3.3 4.8 12 0-19 233 5 3.3 1.7 12 0-20 : 263 9.5 3.3 2.4 15.2 0-22 304 4.1 3.3 3.7 11.1 0-23 199 9.7 3.3 2.9 15.9 0-29 1,284 6.7 .0 0.1 6.8

0-34 2, 031 5.9 .0 .1 6 0-36 104 9.8 3.0 2.8 15.6 Average 7.3 1.9 10.9

Files (heavy)

0-9 0-12

0-14

0-25

0-30

0-31 0-32.

0-33

0-37

Average. _.

1,508 855

1,064 225

9, 550

7, 742

4, 220

2, 041 226

30.3

85.9

23.9

23.6

33.1 28.9

37.2 48.4

61.8

.0.0

3.3 3.3

.0

.0.0

.0 3.0

0.5

.0

.9

1.7 0.1

. 5

30.8

85.9

28.

1

28.6 33.2

29

37.3

48. 5 65.3

41.5 .4 42.9

Law office and library

0-26

0-27 „

369

187

1617.7 0

0

1.9 1.9

17.9

19.6 Average 16.9 1.9 18.8

Library

0-24

0-35 Average

459

2, 533 30.4

19.7 3.30

1.6 035.3

19.7

25.

1

0.8 27.5

Table 10.The percentage of usable floor area in office buildings having combustible contents within given

limits

Combustible contents for usable

floor area

Building 1 Building 2 Build- ingsBuilding 4 Building 5 Building 6

Iblff 0to6

Percent

65

100

25

Percent Percent Percent. Percent Percent

6 to 10 10 to 30

_

30 or more... 0to8 0

1674

10

8 to 10 10 to 15

15 or more

0 to 10 12. 5 7511.4 83

1.6

36

61

1

72.5

8

3 10 to 20

20 to 30

20 or more -. 12.5

30 to 50 4 2

30 or more. . ... 16.5 Total 100 100 100 100 100 100

[22]
Table 11.

Summary data for rooms in school buildings in the District of Columbia, Chevy Chase, Md., and

Bethesda, Md.

Table 11.

Summary data for rooms in school buildings

in the District of Columbia, Chevy Chase, Md., and

Bethesda, Md.—Continued

Combustible contents

Room Survey

no. Room

area Movable property Floor

Exposed wood- work

other than

floor &

Total

40-W b ft'8, 245

lb/ft1 0. 46

lb/ft2 2.6

lb/ft 1 0.6

lb/ft 1 3. 06 Do 44- R 6, 300 1. 75 2.6 .6 4. 95 Do,... 49-CC d 2, 250 0.6 6.2 1.2 8.0

5 598 0. 94 3.8 0.8 5.64

A rt rfirvm 36-R 880 7.1 2.6 2.5 12.2 Do 55-B~"C" 1,024 5.8 1.0 0.5 7.3

Average -- 952 6.5 1.8 1.5 9.8

Bookkeeping 34-R 704 7. 2 2.6 2.2 12.0 Mechanical drawing

Tvpewritine 37-R

33-R. ...

1, 364

704

6. 0 6.22.

6

2.6

2.

0

2.2

10. 6 11.0

Average 924 6.5 2.6 2.

1

11.2

Geography 35-R 704 2.7 2.6 2.2 7.5 Music 47-CC. 782 1. 5 2.

6

2.

6

6.

7

Physics lecture 30-R._._ 736 3.0 6.0 2.0 11.4

Average. . 741 2.4 3.7 2.3 8.5

Typical classroom 4-C ' ._- 765 3. 2 2. 6 1. 3 /. 1 Do 14-W.___ 770 2.

8

2.6 1.1 6. 5 Do 26-R. .. 704 1.7 2.6 2.0' 6.3 Do 41-M 788 3.7

2.8

2.6 2. j 8. 3 Do 48-CC. 828 1.0 4.4 8.2 50-B 759 2.1 1.0 1. 9 5.0

Average /oy 2.7 2.

1

2.1 6.9

45—R 9, 350

4, 428

A Q U. oft Q 2. 5 ==

9. 7 Gymnasium auditori- um.

51-B .35 2.6 2.1 5.

1

Average.. 6, 889 0.33 4.8 2. 6 7. 4

Biology laboratory Do

1-C 20-W—

.

1,020

1,232

891

8 0 L4

2 6 2^6

1 5 L0

12.

1

5^0 Do-._ 27-R 6.1 2.6 2.0 10.7 Do - 53-B 1, 024 4. 5 1.0 0. 4 5. 9

Average 1, 042 5 0 2 2 1 ^ 8 4 Chemistry laboratory.

.

Do —

3-C

28-R

980

828

4.8

6.9

2.6 2.61.5

1.4 8.9

10.9 Do 54-B 1,024 3.5 1.0 0.8 5.3

944 5.1 2.1 1.2 8.4

Clothing laborat ory Foods and clothing lab- oratory.

25-W.... 52-B

1.170

1, 542

5. 2 3.5

2.6

1.0

1.0

3.3 8.87.8

Average 1,356 4.4 1.8 2.2 8.3

Physics laboratory 22-W... 880 1.3 2.6 1.2 5.1 Do - -- 29-R 828 5. 4 2.6 1. 5 9. 5

Average 854 3. 35 2.6 1.4 7.3

Library reading room... Do

11-C...

23-W-_.

3, 180 1,653

1, 736

4 2 7^7 2 g L0

3 4

1.7

10 2 io!4 Do 31-R 9.8 2.6 2.5 14.9 Do 56-B 1,265 7.4 1.0 0.3 8.7 Average 1, 959 7.3 1.8 2.0 11.1

Library stack room Do ... 12-C...

24-W....

528

132 32.825.8

2.6 1.01.2 13.6 36.6 40.4 Do 32-R 132 26.7 2.6 1.5 30.8

Average.. 264 28.4 2.1 5.4 35.9 Lunch room 43-M.... 587 2.6 2.6 1.5 6.7

Office, and file room

Office, home economics.

Office, publications

38-R....

21-W.... 10-C

276

253

1 272

36.3

12. 5 6.9

2.6

3.6

3.6

0.1

1.2 6.0

39.0

17.3

16.5

i lombustible contents

Ex- Room Survey Room Mov posed

no. area able woodprop- Floor work Total

erty other than

floor tt

ft 1 tb/ft2 Ih/ff H'lft 2 lb/ft' Oil ice, teachers. . 2-C 500 6.4 2.6 2.5 11.5 Average 325 15. 5 3.1 2.5 21.1

Storeroom, janitor's 19-W.... 529 16 8 0 0.2 17. 0 Do... 39-R 445 41.6 0 1.2 42.8 DO _. 42—M 86 49. 2 2.

6

3.

2

- Average 353 35. 9 0. 87 1.5 38. 3

Storeroom, lumber 6-C 684 24. 9 0 0.3 25. 2 Do 16-W 276 62. 5 2.6 1.

1

66. 2

480 43. 7 1. 3 0. 7 45.

7

Storeroom , paint .. . . 7-C 115 1.

1

2.6 23. 6 27. 3 Do 17-W.._. 253 6.

9

2.6 2.5 12.0 Average 184 4.0 2.6 13.1 19.7

Storeroom, paper. .. . 8-C 720 92.2 0 0.8 93.0

Tin UO - 13-W 129 112.7 0 .6 103. 3 Average.. 425 97. 5 0 0.7 98.2

Storeroom, textbook 9-C 560 227.0 0 1.0 228.0 Do 18-W„... 945 42. 5 0 0.3 42.8 Do 40-R 794 164. 1 2.6 . 9 167.6 Do 57-B.... 60 255.8 0 0 255. 8 Average 590 172.3 0.7 0.6 173.6 Woodworking shop 5-C 1,917 4.8 2.6 0.4 7.8 Do.. -. 15-W___. 851 7.4 2.6 1.0 11.0 Average 1,384 6. 1 2.6 0.7 9.4

» Doors, windows, baseboard, moulding, etc.

b w—\Voodrow Wilson High School.

0 R—Theodore Roosevelt High School.

d CC—Chevy Chase Elementary School.

• B—Bethesda Chevy Chase High School.

1 C—Central High School.

i M—Ben W. Murch Grade School.

Table 12.

Data taken from certain schools in Washington, D. C, and vicinity showing the percentage of usable

floor area having combustible contents, between certain

limits, in pounds per square foot, and the area of each

floor

Combustible contents

for usable floor area Base- ment Groundfloor First

floor Secondfloor Thirdfloor

Entire

build- ing

Bethesda-Chevy Chase Senior High School (Main Building), Bethesda, Md.

16/ft' 0 to 4.9

Percent Percent Percent

34. 14

62. 83 3.03

Percent

31. 10

65. 35 3.06

0.49

Percent Percent

32. 62

64. 08

3.04

. 26

5 to 9.9-.

10 to 14.9 255.7 (text book store- room)

Total _ 100 100 100

Usable floor area » ft2 ft2 ft2 13, 138

ft'

12, 039

ft' ft'

24, 177

See footnotes at end of table.

4G9723"—42 4* [23]
Table 12.

Data taken from certain schools in Washington, D. C, and vicinity showing the percentage of usable

floor area having combustible contents, between certain

limits, in -pounds per square foot and the area of each

floor—Continued

Combustible contents

for usable floor area Base- ment Ground

floor Firstfloor Second

floor Third

floor

Entire

build- ing

Central High School, Washington , D. C.

lb/ft' 0 to 4.9.. __ -

Percent

88. 34

Percent

72. 61

Percent 67.20Percent 44.20

Percent

55. 87

Percent 66.39

5 to 9.9 9.16 16. 38 25. 19 42.15 38. 85 25. 37

10 to 14.9 4. 98 7. 14 9. 95 4. 06 5.29

15 to 19.9- - .29 .66 0. 19

25 (storerooms).. 2.50 3. 65 0.47 1.77 1. 22 2.00

36.6 (book stack room) 1.27 0. 21 93 (paper storage) 1.26 .33

288 (text book storage) .83 .22

Total 100 100 100 100 100 100

Usable floor area

ft' 42,298ft' 67, 813

ft'

57, 814

ft' 41, 600

ft' 45, 094

ft' 254, 619

Theodore Roosevelt High School (Main Building), Washington, D. C

lb/ft' 0 to 4.9_.

5 to 9.9_ _ 10 to 14.9

Percent 71.97

24. 68

Percent Percent 47.81

25. 47

25. 32

Percent

39. 33 42.81

15.80

Percent

36. 80

32. 81

28. 16

Percent

50. 34 31.03

16. 21 15 to 19.9 1.32 0.26

25 (storerooms). - 0.55 1.23 1.57 .77

30.8 (book stack room) 0.83 .21 39 (office and files) - 0.85 .22

42.8 (storeroom) 1.20 .34

167.6 (text book store- room) 2. 15 .62

Total _.. 100 100 100 100 100

Usable floor area

ft' 35, 970ft' ft'

32, 420

ft' 32, 245

ft' 25, 154

ft' 125, 790 Woodrow Wilson High School (Main Building), Washington, D. C.

Per- Per- Per- Per- Per- PerIblft' cent cent cent cent cent cent

0 to4.9__ 69.12 62. 46 49. 67 35.81 54.60

5 to 9.9_ _ 21. 31 24. 93 38. 96 53. 82 34.41

10 to 14.9 7. 52 7. 38 9. 96 6. 17 15 to 19.9 1. 64 2. 13 0.95

25 (storerooms) - 6. 51 1.40 0.96 0.41 2. 35

40 (text book storage) 0.90 .90 0.24

40.4 (book stack room) .22

42.8 (text book storage) .

.

3.06 .76

66.2 (wood storage) 0.77 .20

103.3 (paper storage) .38 .10

Total 100 100 100 100 100

ft' ft' ft' ft' ft' Usable floor area 35, 165 34,249 31, 959 31,600 130,973 Chevy Chase Elementary School, Chevy Chase, Md.

Iblft' Oto 4.9- —

Percent 82.68

17. 32

Percent Percent

36. 57

57. 15 6.28

Percent

34. 60 65.40

Percent Percent 50.83

47. 11 2.06

5 to 9.9-.

10 to 14.9 Total-. 100 100 100 100

Usable floor area k

ft'

12, 992

ft' ft'

13, 179

ft'

13, 927

ft' ft' 40,098 Ben W. Murch Grade School, Washington, D. C.

lb/ft' Oto 4.9--. _..

Percent Percent Percent

36. 96

57. 98

5.06

Percent

39. 32

59. 08

Percent Percent

38. 14 58.53 2.53

0. 80

5 to 9.9 10 to 14.9 55 (janitor's storeroom) 1.60 Total 100 100 100

Usable floor area • ft' ft' ft'

15, 670

ft'

15, 639

ft' ft'

31, 309

Excludes attic, and basement, which latter contains boiler room only.

' Exclusive of a temporary wooden corridor.

c Exclusive of basement, which contains boiler room only.

Table 13.

Summary data for Medical and Surgical

Building, St. Elizabeths Hospital

Occupancy

Combustible contents

>

33

a > p o

o g

Total

Administrative

Administrative office

ft' Iblft' lb/ft' lb/ft' lb/ft' Iblfl1 6 915 6.30 1.80 8. 10 13. 40 2. 40

Doctors' office. 3 945 5. 70 2. 90 8. 60 14. 40 5. 10 Waiting rooms 3 495 1.40 1.80 3.20 4. 10 2. 10 Nurses' offices and rooms

.

13 1,728 3. 10 1.90 5. 00 12.50 3. 10 Nurses' training school. _ 12 3, 613 2. 20 1.80 4.00 14.50 1. 10 Nurses' infirmary-. 11 1,599 0. 85 2.15 3.00 3.45 2. 50 Library and conference. _ 1 704 5.20 2.50 7.70

Service

Corridors 26 15, 103 2.60 2.65 3.20 0.80 Heating and mechanical

services.. .. - ._ 4 1,009 0.14 0.43 0.51 1.70 0.30

Refrigeration. . _ 5 775 1.90 1.85 3. 75 12. 70 0.0 Kitchen. 7 3, 259 0. 20 0. 33 0. 53 4. 65 0. 10 Laundry. „ 2 336 4.40 0.60 5.00 12.40 3. 80

Janitors' closets and supplies 10 989 1.00 1.40 2.40 7.75 0.90

Stores _ 14 11, 675 1.70 4.00 5.70 19.40 1. 50 Lockers and toilets 8 1,766 0.90 0.50 1.40 2.90 1. 20

Clinical

Surgery __ ... 13 4,307 0.70 1.10 1.80 10.60 0.20 Minor surgery and casts. . 2 390 2. 10 1.10 3.20 3. 80 2.20 Therapy and laboratories- 4 978 2. 80 1.60 4.40 7.30 2.50

Clinics.. 33 7, 421 2. 00 1.90 3.90 21.60 0.50 Dormitories. 32 11,223 0.90 1.60 2.50 3. 60 1.70 Rooms, single 28 3, 511 0.80 1.50 2. 30 3.20 1. 80 Rooms, disturbed patients'. 8 1,016 0.40 2. 50 2.90 3. 20 2.20 Day and waiting rooms.

.

3 720 0.80 2.40 3. 20 3. 80 2.50 Porches, patients' 6 3, 566 0.90 0.40 1.30 2. 30 0. 90

Sterilizers and clothing

stores 4 545 1.40 4.00 5. 40 5. 80 5.00 Pharmacy, dispensary and stores 5 1, 172 5.80 1.90 7. 70 11.50 6. 80 Diet kitchens and patients' dining rooms... 9 1, 755 1.20 2.40 3. 60 5.20 2.70 Lavatories, etc . 22 2,304 0.50 1.40 1.90 5.40 0.30

» Combustible floor finish where present was H-in. thick linoleum, assumed to give equivalent of 1 lb/ft2 combustible material. Table 14.

Summary of part of data for Neuro-psychiatric Continued Treatment Building, St. Elizabeths Hospital

Occupancy

Combustible contents

is S oo o o o

Total

Administrative b

Administrative offices ft' lb/ft* lb/ft' lb/ft' Iblft' lb/ft' and records 2 218 3.4 1.6 5.0 7.3 2.7 Waiting room. 1 128 1.7 1.5 3.2 3.2 3.2

» Combustible floor finish where present was !4-in. thick linoleum, assumed to give equivalent of 1 lb/ft2 of combustible material.

b Two office rooms temporarily vacant having 604 ft3 area are not

included.

[24]
Table 14.

Summary of part of data for Neuro-psychiatric Continued Treatment Building, St. Elizabeths Hospital—Continued

c Combustible contents

Occupancy

room

its

area

Movable

property

-c « c 5f

03 .5 Total

Number

of

un

Total

floor

Woodwork

floor

covei

Average

Maximum Minimum

Service

ft'9

lb/ft' lb/ft' Iblft' Iblft1 Iblft' lblft> Corridors 8, 176 0.0 2.4 2.4 3.2 0.2 Heating and mechanical

2 612 . 7 0.3 1.0 3.3 .8 Laundry rooms and

clothes storage . _ 12 916 12.5 .6 13.1 23.0 1.3 Janitors' closets and supplies. P

1 32 2.9 1.4 4.3 4.3 4.3 Storage room. 1 1,320 2.1 0.0 2.1 2.1 2.1 Lockers, toilets, and bar- ber shop.. _- _ 9 2, 605 0.1 0.1 .2 1.4 0.0

Clinical

Treatment room . 5 4.976 2.4 0.

1

2.5 7.5 0.3 Dormitories..- 13 7, 197 0.7 .8 1.5 4.

1

.5 Single rooms ... 23 2,093 .5 1.6 2.

1

2.5 1.

1

Sitting rooms and porches. 8 7, 680 .7 0.1 0.8 3.1 0.7

Patients' clothing 1 594 .5 .0 .5 0.5 .5 Lavatories, baths, etc 1 360 .0 .1 .1 . 1 .1

Table 15.Summary data for Tuberculosis Infirmary,

St. Elizabeths Hospital

ft 1-4 o

03 Combustible contents

room

its

csCDa Q

o

o.

>>

a « s

.5 Total Occupancy t-i

Number

Total

floi

Movable

ert

Woodwoi

floor

co\

Average

Maximui Minimur

Administrative office and ft1 lb/ft2 Iblft' lb/ft' lb/'t' Iblft' Vilffi records 2 264 0.5 3.0 3.5 3.5 3.5 Doctors' offices .... 2 344 .9 2.0 2.9 3.5 2.3 Attendants' offices.

.

2 248 .3 3.4 3.7 4.4 2.9 Waiting rooms 2 560 .1 1,3 1.4 1.4 1.4

Service

Corridors 2 3,440 0.0 1.2 1.2 1.2 1.2 Mechanical services and

incinerator. . . 3 720 .3 0.2 0.5 0.8 0.3 Kitchens and dining rooms. 3 1,436 .7 1.0 1.7 2.4 .3

Janitors' closets and supplies. 7 476 3.1 3.4 6.5 15.8 4.1 Barber shops, lockers, and toilets _ . 2 624 0.2 1.2 1.4 1.7 1.3

Clinical

Treatment room and

medical supplies. 2 188 0.7 1.0 1.7 2.0 1.5 Dormitories 17 4, 535 .8 2.0 2.8 4.0 1.9 Single bed rooms. . 22 2,312 .5 3.2 3.7 4.0 2.6 Rooms for disturbed

patients.. 2 272 .4 3.3 3.7 3.7 3.7 Porches, patients 4 4,656 .0 1.3 1.3 1.3 1.3

Sterilizers and clothing... 7 1,542 1.7 2.3 4.0 12.7 0.8 Lavatories, baths, etc 8 1,437 0.0 0.5 0.5 0.6 .4

» Combustible floor finish when present was H-in.-thick linoleum, assumed to give equivalent of 1 lb/fts combustible material.

Table 16.

Distribution of combustible contents, Si. Elizabeths Hospital

Combustible contents for usable

floor area

Medical and

Surgical Building

Continued Treatment

Building

Tuberculosis Infirmary

lb/ft' 0 to 4.9. Percent

82.

1

15.4 1.6 0.5

.4

Percent

91.0 7.6

0.7

Percent

93.2 0.3

1.8

4.4 0.3

5 to 9.9 _ 10 to 14.9 15 to 19.9 20 or more .7

ft' 84,535

ft' 36, 964ft'23,92s

Table 17.

Summary data for three warehouses

Combustible contents

Survey

No. Portion of building Floorarea Movable property

Floor

Exposed wood- work

other than

floor

Total

[Basement...

ft'

33, 890

lb/ft' 172.9lb/ft' 6.2lb/ft' " <S ~ lb/ft' 179. 1 1st floor 34, 900

32, 592 23,448

10, 225

223.7 9.7 0 233.4 W-l»„ 2d floor... 105.8 204.0

10 k0.4 116.2 3d floor 6.2 0 210.2 3d floor 61.6 0 0 61.6 3d floor (total) 33, 673 160.8 4.3 0 165. 1

Entire building. ._ 135, 055 166.8 7.5 '0. 1 174.4

[1st floor — 46, 158 44,957

45, 677

45, 677

6.8 0 0 6.8 2d floor 13.6 0 1 14.6 W-2« 3d floor 4 0 1.2 2.2

5.2 4th floor 12.7 0 14.9 5th floor 45, 677

45, 677 8.4 0 1.9 10.3 6th floor 12.2 0 3.8 16.0

Entire building. .

.

273, 823 9.6 0 1.5 11.

1

(1st floor. . 17, 442 17,442

17,442

17,442

0 0 0 0 W-3d J 2d floor 16.2

16.0 0

0

0.8 2.3

17 13d floor 18.3

I 4th floor 10.6 0 2.1 12.7

Entire building. __ *52. 326 14.3 0 1.7 16

» W'-l—Warehouse for printing department,

k Wood partition of 3,360 fbm.

' W-2—Warehouse for department store.

<i W-3—Warehouse for department store.

• Not including first floor which is used only for merchandise in transit.

CHAPTER IV. FIRE-RESISTANCE RATINGS FOR BUILDING CONSTRUCTION

AND MATERIALS

1. Fire-Resistance Ratings for Load-Bearing Masonry Walls

(a) Test Conditions

The fire tests cited below were conducted in

substantial accord with the Standard Specifications for Fire Tests of Building Construction

and Materials, ASA No. A2-1934. According

to this specification, average indicated furnace

temperatures are required to conform to the

[25]
following values within allowable tolerance

limits: 1,000° F at 5 min,

1,300° F at 10 min,

1,550° F at 30 min,

1,700° F at 1 hr,

1,850° F at 2 hr,

2,000° F at 4 hr,

2,300° F at 8 hi-, and continues at 2,300° F. The fire-resistance period is taken to be

reached if: (1) An average temperature rise of 250° F

or a maximum rise of 325° F, measured with

thermocouples under asbestos pads, is attained on the unexposed side of the wall.

(2) Passage of heat, flame, or gases hot

enough to ignite cotton waste occurs.

(3) Failure under the design load occurs

(load-bearing constructions only).

Walls must also stand the fire and hosestream test and, for load-bearing construction,

the loading test within 72 hi' after the completion of the fire-and-hose test. Most of the. brick test walls were laid up in 1:1:6 portland cement-lime mortar. Some solid walls were laid up in 1:3 portland cement or 1:3 lime mortar, these proportions being based on volume of cementing materials to that of damp

sand. They were tested restrained within the

panel frame, unrestrained with freedom for ex- pansion and deflection at sides and top, or under a constant working load of 160 lb/in. 2 of gross area, except that the 4-in. walls without

pilasters were loaded to 80 lb/in. 2 The ratings

for 8-in. or heavier solid walls can be taken to apply if laid in any of these mortars. For 4-in. solid walls and all hollow walls the mortar mix

should be not leaner than 1:1:6 proportion.

The structural tile walls were laid in 1:1:4 and those of concrete blocks in 1:1:6 portland

cement-lime mortar. The respective ratings

given should be taken as applying where mortar

mixes not leaner than these are used. The

walls were loaded during the fire test to 80 lb/in. 2 of gross area. The hollow brick walls with 70 percent of solid material were loaded to 120 lb/in. 2 and

with 87 percent of solid material to 160 lb/in. 2 of gross area. The brick cavity wall made up of 2 wythes of brick laid flat with a % in. metal tie

between them for each 3 ft2 of surface is rated

for an average working load of 40 lb/in. 2 of gross area which may be applied eccentrically

to give a maximum stress at the fire-exposed

surface of 80 lb. /in. 2

(b) Sources oj Data

(1) Fire resistance of hollow load-bearing viall

tile, BS J. Research 2, 1 (1929) RP37.

(2) "Fire resistance of concrete masonry

units" by Carl A. Menzel, Portland Cement

Association, January 1934.

(3) Original data from National Bureau of Standards tests of brick and heavy structural

tile (clay or shale) walls, partly summarized in Letter Circulars LC 228 and 229.

(4) Underwriters' Laboratories tests of concrete masonry walls.

(5) Unpublished results of recent tests of concrete masonry walls at the National Bureau

of Standards.

(c) Extension and Interpolation of Test Results

When the test data were directly applicable,

the ratings were taken generally at a little below the average of the test results where there was an appreciable variation. A few ratings are based on limited interpolation and extension of a line of related test data made by the

method given in section 1 of appendix B.

(d) Effect of Plaster

The constants for use in the formula for determining the fire resistance of plastered walls

given near the end of section 1 of appendix B

were derived from available test results, and

all the ratings for plastered walls were made by

the use of this formula. The average thickness

of plaster applied in the different series of

tests ranged from % to % in. The thickness for

which ratings are given are those most likely to obtain in building construction considering

what must be done to obtain a true surface.

Thus ratings for plastered brick and concrete block walls are for %-in. plaster thickness and

in the case of structural clay tile for %-in. thickness. Ratings for other thicknesses can be

obtained by substituting the appropriate

constants in the formula.

Tests of four hollow concrete-unit walls show

the effect of one coat of plaster on the fire- exposed side to be about the same as for one

[26]
coat of plaster on the unexposed side. No tests have been made with plaster on the unexposed

side only of clay hollow-tile walls. However,

the ratings given in the table for plaster on one

side are believed to have sufficient margin of safety to be applicable for either condition.

(e) Combustible Members Framed into Wall

The fire-resistance period, when combustible

members are framed into the wall, is taken to be

reached when an average temperature rise of

325° F, or a maximum rise of 422° F, is attained

at a point 3% to 4 in. from the side not exposed

to fire. Average test results show that the ratings for unplastered Avails into which combustible members project will be the following parts of the

rating for the same unplastered walls not thus

modified. These factors may be applied where

definite test data are lacking.

(1) All walls with 1 cell in wall thick- ness two-fifths.

-in. walls with 3 cells in wall thickness two-fifths.

8-in. walls with 2 units in wall thickness two-fifths.

8-in. solid walls two-fifths.

All walls with 2 cells in wall thick- ness one-half.

All 12-in. walls (except walls with

1 or 2 cells in wall thickness) two-thirds. If such walls are plastered with K-in. 1:3 sanded gypsum plaster on the side opposite the

(2) 8-

(3)

(4)

(5)

(6)

framing, add % hi if the rating for combustible

members framed into the unplastered walls is 2% hr or less, and add 1 hr if the rating is 3 hr

or more. For plaster thickness these

increments are somewhat greater, as indicated

in the ratings for walls of clay or shale structural

tile. For plaster on the same side as the framing and for plaster on one side of walls with combustible members entering from both sides, no

increase in fire resistance due to the plaster can

be assumed, since the wall may be exposed to

fire on the unplastered side. If hollow spaces (cells) surrounding the ends

of combustible members are filled solidly with

masonry the rating will be the same as for in- combustible or no members framed into the

wall, except that the rating cannot exceed the

rating for solid walls of the same thickness with

combustible framing. These limits can be

taken as follows:

8-in. walls unplastered 2 hr.

8-in. walls plastered on fire-exposed side or both sides 2J4 hr. 12-in. walls unplastered 7 hr. 12-in. walls plastered on fire-exposed side or both sides 8 nr.

(J) Fire-Resistance Ratings

Fire-resistance ratings for masonry walls are given in tables 18 to 23, inclusive. All are rated

as load-bearing unless otherwise noted.

Table 18.Load-bearing brick walls

Nominal wall thickness

8_.

12.

12

9 to 10.

4

12.

Type of wall

Soliddo

do Hollow Rolok

do Hollow Rolok Bak.

do Cavity

Soliddo

do

do... do

do.

Material

Clav or shale. do

do

dodo

do

do

do

Concrete do

do. Sand-lime dodo

Ultimate fire-resistance period

Incombustible members

framed into wall or no

framed-in members

No plaster

hr

5

» 102H

54

10

5m6

13m7

i> 10

Plaster on one

side

G »10

36

5

106

2

7

141Yi 8

b 10

Plaster on two

sides

hr

712

4

7

8

16

39

b 12

Combustible members framed into wall

No plas- ter

hr

2H

8

"iy2

Plaster on

exposed

side

hr

2>2 9w4

2J4

» Based on load failure. If based on temperature rise, the fire-resistance period would bo 12 hr for the unplastered wall, 13 hr for plaster on one side, and 15 hr for plaster on both sides.

b Based on wall failure at 10 hr. If based on temperature rise, the fire-resistance period would be 14 hr for the unplastered wall, 15 hr for plaster oc one <i«. and 17 hr for plaster on both sides. Note.—Not less than 3-£-in. 1 : 3 sanded gypsum plaster is required to develop the above ratings for plastered walls.

[27]
Table 19.

Load-bearing walls of clay, or shale, cored

bricks Table 21.

Load-bearing brick-faced walls of clay, or

shale, structural tile

Nominal wall thickness

Units

in

wall

thickness

Cells

in

wall

thickness

Minimum

percentage

of

solid

materials

in

units

Ultimate fire-resistance period

Incombustible members framed

into wall or no

framed-in members

Combustible members

framed

into wall

No

plaster

Plaster

on

one

side

Plaster

on

two

sides

No

plaster

Plaster

on

exposed

side

in. Ar hr Ar hr hr 8 1 1 70 2K 3 4 1 VA

12 ____ 1 2 70 5 6 7 3 4 8 . 2 2 87 5 6 7 2 m 12 3 3 87 "10 "10 -12 8 9

* Based on load failure. If based on temperature rise, the fire-resist ance

period would be 11 hr for the unplastered wall, 12 hr for plaster on one

side, and 14 hr for plaster on both sides. Note.—Not less than A in. of 1:3 sanded gypsum plaster is required

to develop the above ratings for plastered walls. Table 20.- -Load-bearing walls of clay, or shale, struc- tural tile

Nominal wall thickness

ra. 8

88

8

8

8

8

8

12

1212

12

12 L 12

16

16

16

1616

16

2

2

2 2or3 2or3

2 or 3

2 or 3 2or3 2or3

22

2

2

3 or 4

3 or 4

3 or 4 3or4

3

3

3

3 or 4

3 or 4

3 or 4

4 or 5 4 or 5 4 or 5

5 or 6

5 or 6

5 or 6

Ultimate fire-resistance period

Incombustible members framed

into wall or no

framed-in members

hrW

iy2 W2

IS

22K

32M

3VA

IV.

4

! 55

6

7

10

^2

hr2

2VA

32K

3V/i

4VA

44

45

6

6

7

10

11

Ar

3

3VA

43K

44

54

5

6

78

9

10

1112

13

Combustible members

framed

into wall

Ar

1V4

*A

3A

l

22^

3

22Al 3

4

4

55

« a

hrVAm

o1A

lli M2

3SA

4

33A

4

5

56

6

The percentage of solid material in units given above, in the case of walls built up of units of different designs,' is to be taken as the weighted

average for the units at the courses in the wall where the average per- centage is the lowest, i Notes.—All tile is to conform with ASTM specifications from the standpoint of strength and absorption. Not less than H-ia. of 1 : 3 sanded gypsum plaster is required to develop

the above ratings for plastered walls.

Nominal

wall Description

Ultimate fire- resistance period

thickness No

plaster Plasterinside

in. 8 4-in. 40 percent solid tile plus 4-in. brick

face.

8-in. 40 percent solid tile plus 4-in. brick

face.

8-in. 70 percent solid tile plus 4-in. brick

face.

Ar3H

6

Ar

4

12 7

12 « 10

a Based on w

r all failure under load. If based on temperature rise, the ultimate fire-resistance period would be 11 hr for the unplastered wall and 12 hr for the wall plastered on one side. Note.—Not less than $6-in. of 1:3 sanded gypsum plaster required to develop the above ratings for plastered walls.

Table 22.

Load-bearing furred and cavity walls of

clay, or shale, structural tile

Ultimate fire- resistance Nominal period wall Description

thickness Plaster Plaster on one on two

side sides

in. Ar Ar 8 - 8-in. 40 percent solid tile plus 2-in. fur- ring tile - 5

10._ — Two 3M-in. 40 percent solid tiles with

2-in. air space between 4

Note.—Not less than %-in. Portland cement plaster or stucco outside and 5£-in. gypsum plaster inside is required to develop these ratings.

Table 23. -Load-bearing walls of cored concrete masonry

units

Units in wall thickness a_

3 0

Ultimate fire-resist- ance period

Incombustible or no members

framed

into wall

s

Combustible members

framed

into wall

S a

P4

A. Units made with expanded slag or pumice aggregates

in. Percent

Ar Ar Ar Ar hr

6 1 70 3 4 5

6 1 76 3H 4 5 8 1 55 3 4 5 W 8 1 62 4 5 6 m 2

10 1 60 5 6 7 2 2H

10 2 2 62 4 5 6 m 2 Cavity type 2-in. air space.

[28]
Table 23.

Load-bearmg v>alls of cored concrete masonry

units—Continued

Units in wall thickness

a

0

f

sol unit

w

O 4> 0ao

intag

;oiicr is

& H 1-4 a

9 oj a" CO O

3

Ultimate flre-resist- ance period

Incombustible or no members

framed

into wall

a °

Combustible members

framed

into wall

B. Units made with expanded burned clay or shale, crushed limestone,

air-cooled slag, or cinders

10

-in. brick face.

2%-in. brick face. 2Cavity type 2-in. air space.

hr Ar ftr Ar Ar

52 2 2H 3K U IK

62 2H 3 4 l IK

70 3 4 5 IK 2 60 4 5 6 1H 2

55 4 5 6 IK 2 62 5 6 7 2 2K

65 3K 4 5 IK IK

65 7 8 9 4 5 62 5 6

62

62

43H5

4 5 IK 2

C. Units made with calcareous sand and gravel. Coarse aggregate, 60 percent or more calcite and dolomite

10' 2„ 2 62 IK IK 5 IK IK

Cavity type 2-in. air space.

D. Units made with siliceous sand and gravel. Ninety percent or more

quartz, chert, or flint

8 1 1 54 K H H % K

12 1 1 57 5/l2 5/\2 6 Ms 2K

12 2 2 55 5 6 7 2 2K

Note.—Not less than"K-in. 1 :3 sanded gypsum plaster is required to develop the above ratings for plastered walls.

2. Fire-Resistance Ratings for Masonry

Partitions

(a) Test Conditions

The fire tests upon which the ratings are based were conducted in substantial accord

with the Standard Specifications for Fire Tests

of Building Construction and Materials, ASA

No. A2-1934, the fire-resistance period being

taken to be reached if any of the following

occurs:

1. An average temperature rise of 250° F

or a maximum rise of 325° F, measured with

thermocouples under asbestos pads, is at- tained on the unexposed side of the partition.

2. Structural collapse or passage of flame

or of gases hot enough to ignite cotton waste. For a full rating the requirements of the

hose-stream test also must be met. Partitions

having ratings of less than 1 hr require no

hose-stream test. Those having ratings of 1 hr

or more require a hose-stream test after a fire exposure equal to one-half the rating period,

except that for ratings of more than 2 hr the

fire exposure before the hose-steam test need

not be of more than 1-hr duration.

(6) Sources of data

(1) Magnesium oxy'sulfate wood-fiber blocks.—

The ratings were taken directly from the results

of fire tests conducted at the Underwriters'

Laboratories and the National Bureau of Standards. The material is shredded wood (excelsior)

bound with magnesium oxysulfate cement.

(2) Hollow glass blocks. —The rating was

taken directly from the results of fire tests conducted at the Underwriters' Laboratories.

The rating given is for glass blocks used as

partition material and not as an opening

protective.

(3) Gypsum blocks.—The ratings were based on fire tests conducted at the Underwriters'

Laboratories and Ohio State University (Ohio

Engineering Experiment Station Bulletin No.

104, A Study of the Fire Resistance of Building

Materials, January 1940, and more recent

tests), the ratings being limited by considerations of the stability of the partition when

exposed to fire rather than by temperature rise on the unexposed side.

(4) Structural clay tile. —The ratings repre- sent the lower averages of the results of fire tests conducted at the National Bureau of

Standards and Ohio State University (Ohio

Engineering Experiment Station Bulletin No.

104, A Study of the Fire Resistance of Building

Materials, January 1940).

[29]
(5) Hollow concrete units.—The ratings repre- sent the lower averages of the results of fire tests conducted at' the National Bureau of

Standards and by the Portland Cement Association (Tests of the Fire Resistance and

Strength of Walls of Concrete Masonry Units,

January 1934). These results, as for structural

clay title, have been interpolated and extended

according to the principles outlined in appendix

B, section 1, chiefly for the ratings of some of the plastered constructions.

(c) Fire-Resistance Ratings

Fire-resistance ratings for masonry partitions are given in tables 24 to 26, inclusive. They

are aU rated as nonhealing.

Table 24.

Miscellaneous nonb ear ing masonry partitions

Description

Ultimate fire-resist- ance period No

plaster

Plaster on both

sides Magnesium oxysulfate wood-fiber blocks »

2-in. blocks laid in Portland cement-lime mortar

ftr ftr

1 3-in. blocks laid in portland cement-lime mortar 2

Hollow glass blocks

8- by i

7A-in. blocks 'A 7A-m. thick, weight 4 lb each; Portland cement-lime mortar, horizontal mortar

joints reinforced with metal lath Yt Gypsum blocks k

2-in. solid blocks. 1 3-in. blocks not less than 70-percent solid... 1 2

3

6

4-in. hollow blocks . .. . 5-in. solid blocks. 4 "Not less than J4-in. thickness of 1:3 sanded gypsum plaster is re- quired to develop the above ratings for plastered partitions.

k Laid in 1: 3 sanded gypsum mortar. Voids in hollow blocks to be not more than 30 percent. Not less than M-in. thickness of 1:3 sanded gyp- sum plaster is required to develop the above ratiDgs for plastered partitions. Table 25.

Structural clay tile partitions

[Laid in portland cement-lime mortar]

Ultimate fire resistance period

Description No plaster Plaster on unex- posed side Plaster on fire-ex- posed side Plaster on both

sides 4

(A) (B) (A) (B) (A) (B) (A) (B)

One cell in wall thickness

ftr min hr min ftr min ftr min ftr min ftr min ftr min ftr min

3-in. partition, units not less than 50-percent solid . .... 0 10 0 20 0 20 0 20 0 30 0 45 0 45

4-in. partition, units not less than 40-percent solid ... . 10 20 20 25 30 45 45

4-in. partition, units not less than 50-percent solid. 15 25 25 30 45 1 1 1 15

6-in. partition, units not less than 30-percent solid 15 20 25 35 45 1 1 15 1 30

6-in. partition, units not less than 40-percent solid ... 20 25 30 40 1 1 05 1 15 1 30

Two cells in wall thickness

4-in. partition, units not less than 50-percent solid.. ... ...

4-in. partition, units not less than 60-percent solid . 6-in. partition, units not less than 45-percent solid . ..

25

3045

30

35

1

35

40

1

45

1

1 15

1

1 15

1 15

1 IS

1 30

1 30

1 15

1 30

1 30

1 30

22

Double shells plus one cell in wall thickness

4-in. partition, units not less than 45-percent solid 20 25 30 35 45 1 1 15 1 30

One cell in wall thickness, cells filled with broken tile, crushed stone, slag, cinders, or sand, mixed with mortar

4-in. partition, units not less than 40-percent solid . 6-in. partition, units not less than 30-percent solid1 15

2

1 15

2

1 30

2 30

1 30

2 30

1 45

2 30

1 45

2 30

2 30

3 30

2 30

3 30

Notes.—Ratings in column (A) are for dense hard-burned clay or shale tile- Ratings in column (B) are for medium-burned clay tile. All shale tile are classed under (A). Not less than 56-in. thickness of 1: 3 sanded gypsum plaster is required to develop the above ratings for plastered partitions.

[30]
Table 26.

Partitions of hollow concrete units

[Ratings based on one unit and one cell in wall thickness]

Ultimate fire-resistance period

Partition No

plaster

Plaster on one

side

Plaster on two

sides

A. Units made with expanded slag or pumice aggregates

3-in. partition, unit not less than 73 percent

solid...

4- in. partition, units not less than 62 percent

solid

4-in. partition, units not less than 73 percent

solid

6-in. partition, units not less than 49 percent

solid

6-in. partition, units not less than 62 percent

solid

6-in. partition, units not. less than 73 percent

solid

ftr ftr 1 m

m m

m 2

114 2

2 23^

3 4

ftr2

5

B. Units made with crushed limestone, blast furnace slag, cinders, and

expanded burned clay or shale

3-in. partition, units not less than 73 percent

solid H m 4-in. partition, units not less than 65 percent

solid. ... . ... . 1 2

4-in. partition, units not less than 73 percent

solid.. 1M m 2

6-in. partition, units not less than 49 percent

soild M m 2

6-in. partition, units not less than 62 percent

solid .. m 2 2^

6-in. partition, units not less than 73 percent

solid .. . ... 2H 3 4

C. Units made with calcareous sand and gravel. Coarse aggregate, 60 percent or more calcite and dolomite

4-in. partition, units not less than 62 percent

solid... % m

D. Units made with siliceous sand and gravel

quartz, chert, or flint Ninety percent or more

4-in. partition, units not less than 73 percent

solid -. a M i

Note.—Not less than }^-in. thickness of 1 : 3 sanded gypsum plaster is required to develop the above ratings for plastered partitions.

3. Fire-Resistance Ratings for SteelFramed Partitions and Steel-Framed

Brick-Veneered Walls

(a) Test Conditions

The fire tests upon which the ratings are based were conducted in substantial accord with

the Standard Specifications for Fire Tests of Building Construction and Materials, ASA No.

A2-1934. (See under section 1 (a), "FireResistance Ratings for Load-Bearing Masonry

Walls," or under section 4 (a), "Fire-Resistance

Ratings for Wood- and Metal-Framed Partitions.")

(b) Source of Data

The ratings given herein were taken directly

from the results of fire tests conducted at the

National Bureau of Standards.

(c) Plaster

Plaster proportions are given hi the tables as weight of diy plaster to dry sand. The ratings can be taken to apply if a finish coat is included

in the given plaster thickness. See "FireResistance Ratings for Wood- and Metal-Frame

Partitions," page 33, for the method of

measuring plaster thickness. The plaster

thickness is taken from the back of flat lath

and the back of the flat portion of ribbed lath. Plaster noted as "neat" is to taken as unsanded

wood-fiber gypsum plaster.

(d) Fire-Resistance Ratings

The ratings given in tables 27 and 28 are for the indicated facings secured to lightweight

steel studs not less than 3 in. in depth. The

spacing of the studs will be governed by the

loading, the ratings being for loads developing

a stress of not more than 7,270 lb/in. 2 of the

net area of the steel studs for the partitions and

5,120 lb/in.2 for the brick-veneered walls. The

spacing of the studs is to be such as to afford

adequate rigidity to the metal-lath or gypsumplaster base. All constructions are rated as load-bearing and designated as "combustible"

only when noted.

Table 27.

Steel-framed partitions

Partitions faced on both sides withM-in. sanded gypsum plaster, 1: 2for scratch coat and 1:3 for brown coat, on metal lath M-in. sanded gypsum plaster, 1 : 2 for scratch and brown

coats %-in. sanded gypsum plaster, 1 : 2 for scratch coat and 1:3 for brown coat, on metal lath %-in. sanded gypsum plaster, 1:2 for scratch and brown

coats, on metal lath _.. K-in. neat gypsum plaster on metai lath

1-in. neat gypsum plaster on metal lath

Ultimate

fire-resist- ance period

ftr

1

1IK »2m

» For partitions loaded not to exceed 5,120 lb/in.2 of stud area the rating

is 2}^ nr.

469723°—42 5 [31]
Table 28.

Steel-framed brick-veneered walls

Brick-veneered walls faced a? indicated

On one side, of 1-in. magnesium oxysulfate wood fiber- board sheathing attached to studs, 1-in. air space, and 3?i-in. brick secured with metal ties to steel frame every fifth course. Inside facing of %-in. 1:2 sanded gypsum plaster on metal lath secured di- rectly to studs Same as above except with yi-ia. vermiculite plaster

for inside facing.^ On one side, of H-in. wood fiberboard sheathing next

to studs, ?i-in. air space formed with ?4-by 1%-in. wood strips placed over the fiberboard and secured

to the studs; paper-backed wire lath nailed to these

strips, 3^4 -in. brick veneer held in place by filling a H-in. space between the brick and paper-backed lath with mortar. Inside facing of 5i-in. neat gypsum

plaster on metal lath attached to 5i6-in. plywood

strips secured to edges of the studs. Rated as "combustible" on account of the sheathing. On one side, of paper-backed wire lath attached to studs and 334-in. brick veneer held in place by filling a 1-in. space between the brick and the lath with

mortar. Inside facing of 1-in. paper-enclosed

mineral-wool' blanket weighing 0.6 lb/ft 2 attached

to studs, metal lath or paper-backed wire lath laid over the blanket and attached to the studs, and %-

in. sanded gypsum plaster, 1:2 for the scratch and

1 : 3 for the brown coat _.

Ultimate fire- resistance period

Plaster

side exposed

m

2

Brickfaced

side exposed

ftr

4. Fire-Resistance Ratings for Wood- and

Metal-Framed Partitions

(a) Test Conditions

The fire tests upon which the ratings are based were conducted in substantial accord with

the Standard Specifications for Fire Tests of

Building Constructions and Materials, ASA

No. A2—1934, the fire-resistance period being

taken to be reached if: (1) An average temperature rise of 250° F or

a maximum rise of 325° F, measured with

thermocouples under asbestos pads, is attained on the unexposed side of the partition.

(2) Passage of heat, flame, or gases hot

enough to ignite cotton waste occurs.

(3) Failure under the design load occurs

(load-bearing constructions only).

For a full rating the requirements of the hosestream test must be met. Partitions having

ratings less than 1 hr require no hose-stream

test. Those having rating of 1 hr or more re- quire a hose-stream test after a fire exposure

equal to one-half the time of the rating, except

that for ratings of more than 2 hr the fire exposure before the hose-stream test need not be

of more than 1-hr duration.

Partitions involving material which burns

freely during the fire test or continues to flame

after the furnace fire is shut off are rated as "combustible."

Only wood-stud partitions were tested under

load, the loading being on the basis of 360 lb/in. 2 of the net area of the studs.

(b) Sources of Data

Results of fire tests of 147 wood- and metalframed partitions conducted at the National

Bureau of Standards (see Building Materials

and Structures Report BMS71) and 9 fire tests of wood frame partitions conducted at the

Underwriters' Laboratories were used as a basis for the ratings given herein.

(c) Interpolation of Test Results

Most of the ratings were taken directly from

the test results and represent the lower averages

of results of tests in the case of duplicate or

similar partition tests. Some of the ratings for partitions having facings of sanded gypsum

plaster on metal lath were interpolated ac- cording to the method given in appendix B,

section 1. Partitions which were not subjected

to the hose-stream test have been given ratings on the basis of comparisons made with similar

partitions that have qualified under the hosestream test. Accordingly, all partitions rated can be taken as having met such requirements.

(d) Framing

(1) Wood framing.—Ratings are for 2- by

4-in, (nominal size) wood studs (No. 1 Common or better) set edgewise and having 2- by

4-in. wood plates at top and bottom and

stayed transversely at midheight with wood

blocking.

(2) Metal-Framed, Hollow Partitions.—Ratings are for any usual type of nonbearing metal

framing providing not less than 2-in. air space.

(3) Metal-Framed, Solid Partitions.—Ratings

are for %-in. channel framing or, in the case of sprayed-on portland cement mortar, reinforcement of 4-in. square mesh of No. 6 gage wire

welded at intersections (no channels).

[32]
(e) Firestopping

The actual protection given by a partition

construction may be less than the rated fire resistance because of passage of fire around the

borders of the partition. To prevent this occurrence the spaces in the wood framing adjoining the partition must be closed or filled, preferably with incombustible material.

(/) Mineral-Wool Fill

For the ratings here given "mineral-wool fill" can be taken as rock-wool bats weighing not less than 1.0 lb/ft2 of wall surface, glass-wool bats

at 0.6 lb/ft2

, or rock wool blown in and weighing

not less than 2.0 lb/ft2 of wall surface. "Wall

surface" above applies only to surface of filled space. Where particular methods of securing

the fill in place are required, this is noted in the

tables.

(g) Board Facings and Plaster Bases

"Fiberboard" can be taken as wood or cane

fiberboard of light or medium density, the minimum weights being as given in the tables. "Metal lath" can be taken as expanded metal,

wire lath, or paper-backed expanded metal or wire lath, the weights to be as usually specified

for the different types of construction. Other

types of board facings and plaster bases are as given in the tables.

(h) Plaster

Plaster measurements are taken from the face

of the plaster base except that for metal lath the

thickness is measured from the back of the lath. For corrugated or ribbed plaster bases the thick- ness is taken as the average thickness of plaster

applied to the base. Plaster proportions are given in the tables as weights of dry plaster to dry sand, the first ratio being for the scratch coat

and the second for the brown coat. The ratings can be taken to apply if a finish coat is included

in the given plaster thickness. Mixtures richer

in plaster can be substituted for those given.

Where other aggregates than sand are used,

these are indicated, the last figure in the combination being for the sand. Plaster noted as "neat" is to be taken as unsanded wood-fiber

gypsum plaster.

Volumes of loose damp sand corresponding to the required weights of dry sand, assuming dry

sand to weigh 100 lb/ft3

, are given in table 29,

which is arranged for convenient use with half

bags and full bags of gypsnm plaster, Keene's

cement, hydrated lime, and portland cement as plaster components of the mix.

Table 29.Required volumes of damp sand, assumed

shoveled in, for given weights of dry sand

Percentage of moisture in sand

Weights of dry sand

25lb

50

lb

100

lb 200

lb 300

lb 94lb

188 lb 282

lb

376

lb

ft3 ft" ft3 ftl ft3 ft3 ft3 ft3 ft3 0.25 0.50 1.00 2. 00 3.00 0.94 1.88 2. 82 3. 76 .28 .56 1.12 2. 24 3. 36 1.05 2. 10 3.16 4. 21 .30 .60 1. 20 2.40 3. 60 1.13 2.26 3.38 4. 51

.31 .63 1.26 2. 52 3. 78 1.18 2.37 3. 55 4. 74 .32 .64 1.28 2. 56 3. 84 1.20 2. 40 3. 61 4. 81 .31 .63 1.26 2. 62 3.78 1.18 2.37 3.55 4. 74 wl .30 .61 1. 22 2. 44 3. 66 1. 15 2.30 3.44 4.59

12 . 29 .58 1. 16 2. 32 3. 48 1.09 2.18 3.27 4. 36 Average, 2 to 10 .31 .62 1.25 2.50 3. 75 1. 17 2. 35 3. 52 4. 70

The percentage of moisture is obtained by

dividing the loss of weight on drying at a temperature above 212° F by the dry weight of the

sample. Where the moisture content of the

sand is not known but it is damp, although not

so wet that water comes out of it, the values

given in the last line of the table can be used

with a fair degree of approximation.

The volume in cubic feet of containers used

for measuring sand may be determined by di- viding the increase in weight due to filling with

water by 62.4.

(i) Fire-Resistance Ratings

All partitions, the ratings for which are given

in table 30, are assumed to have identical fac- ings on both sides and are rated as load-bearing

unless otherwise noted. They are designated

as "combustible" according to the test specifications on account of the wood framing.

133]
Table 30.

Wood-framed partitions

[Rated as load-bearing except as noted]

Description-. . Ultimate fire-resistance period

Thickness of board or plaster in facing %-in. %-in. %-in. %-in. 1-in.

Facings of Boards Without Plaster

Fiberboard weighing 0.7 lb/ft 2 hr min hr min

10

1530

hr min

20

35

45

hr min hr min

Fiberboard weighing 1.1 lb/ft 2 __ __ Flameproofed fiberboard weighing 1.6 lb/ft 2 as treated Tonguc-and-grooved wood boards Tongue-and-grooved wood boards with mineral-wool fill ._ _ . Tongue-and-grooved wood boards with asbestos paper weighing 30 lb/100 ft 2 between

boards and studs _. - .. .._ Gypsum wallboard _ _ ... ... Gypsum wallboard with mineral-wool fill _ _ _. _ 25 4045

1

1 Gypsum wallboard with mineral-wool fill, rated as nonbearing- _ _ Gypsum wallboard with mineral-wool bats nailed to studs ._

Facings of Plaster on Wood Lath

1:2, 1:3 gypsum plaster

1:2, 1:3 gypsum plaster with mineral-wool fill. 1:6, 1:7.5 lime plaster

1:5, 1:7.5 lime plaster with mineral-wool fill...

30

3045

Facings of Plaster on Board Plaster Bases

1:2, 1:2 gypsum plaster on %-in. fiberboard weighing 0.7 lb/ft 2__ _ _ 1 : 2, 1 : 2 gypsum plaster on %-in. flame-proofed fiberboard weighing 2.8 lb/ft 2 as treated- - 1:3, 1:3 gypsum plaster on 1-in. magnesium oxysulfate wood fiberboard Neat gypsum plaster on %-in. plain gypsum lath.

1:2, 1:2 gypsum plaster on %-in. plain gypsum lath with 1%- by 1%-in. metal lath pads

nailed 8-in. centers vertically, 16-in. centers horizontally.

1:2, 1:2 gypsum plaster on %-in. perforated gypsum lath, one %-in. diameter hole or

larger per not more than 16 in. 2 of lath surface

1:2, 1:2 gypsum plaster on %-in. gypsum lath, plain, indented, or perforated other than

as above

35

45

45

Facings of Plaster on Metal Lath

1:2, 1:3 gypsum plaster

1:2, 1:3 gypsum plaster with mineral-wool fill 1:2, 1:2 gypsum plaster

1:2, 1:2 gypsum plaster with mineral-wool fill Neat gypsum plaster Neat gypsum plaster rated as nonbearing

1:2, 1:3 Portland cement plaster

1:1/30:2, 1:1/30:3 Portland cement and asbestos fiber plaster.

1:5, 1:7.5 lime plaster

2:1:8, 2:1:10 lime and portland cement plaster

2:1:8, 2:1:12 lime and Keene's cement plaster

The steel-framed hollow partitions listed in

table 31 have facings on both sides of plaster on metal lath. They are rated as nonbearing

partitions on account of the nonbearing types

of framing used.

Table 31.Steel-framed hollow partitions, nonbearing

[Facings of plaster on metal lath]

Thickness of plaster ___ . %-in

1:2, 1:3 gypsum plaster

1:2, 1:2 gypsum plaster _ 1:%. 1:% gypsum plaster Neat gypsum plaster . 1:2, 1:3 Portland cement. _ 1 : 1/30 : 2, 1 : 1/30 : 3 portland cement and asbestos

fiber plaster

Ultimate fire-resistance period

hr hr % 1 1%

1 1% 1% 1% 2 i% 2 2%

% %

U 1

The steel-framed solid partitions covered in

table 32 are also rated as nonbearing on account

of the framing used, which was of %- or 1-in. hot-rolled or strip-steel channels.

Table 32.

Steel-framed solid partitions, nonbearing

[Body and facings of plaster on metal lath]

Thickness of plaster _ 2 in.

1:2%, 1:2% gypsum plaster on 1 in. mag- nesium oxysulfate wood fiberboard...

1:2, 1:2 gypsum on % asbestos lath (soft) 1:2, 1:3 gypsum plaster on metal lath

1:2, 1:2 gypsum plaster on metal lath

1:1, 1:1 gypsum piaster on metal lath 1:%, 1:% gypsum plaster on metal lath Neat gypsum plaster on metal lath

1:2, 1:3 portland cement on metal lath

1:4, 1:4 portland cement sprayed on wire mesh.

4.5:1:7, 4.5:1:7 Portland cement, sawdust, and

sand sprayed on wire mesh

2% in. 2% in.

Ultimate fire-resistance period

-wftr hr

-1 %% 1 % 1 1 1 1% 1%

1% 1% 2 1% 2 2%

% %

a

i

[34]
(j) Partition Facings as Fire-Protective Finishes

over Wood Framing

Temperature measurements taken on the face

of the studs during tests of partitions in which

the framing was of wood indicated the effec- tiveness of the facings in affording protection

to combustible members. In conformity with

the tests specifications, the limit of protection

is assumed to be reached when an average temperature rise of 250° F above the initial occurs on the face of the wood supports, or a rise at any one thermocouple location of 325° F. The

ratings for this condition are given in table 33.

Table 33.Fire-protective finishes over wood framing

Facings

)4-in. flberboard _ _ J<£-in. flberboard flameproofed

J4-in. flberboard with ^-tn. 1:2, 1:2 gypsum plaster

7/i-in. flameproofed flberboard with J^-in. 1:2, 1:2 gypsum

plaster ... 5^-in. gypsum wallboard gypsum wallboard.. _ %-in. plain or indented gypsum lath with H-in. 1:2, 1:2 gypsum plaster

5-6-in. perforated gypsum lath with yi-in. 1:2, 1:2 gypsum

plaster Wood lath with J/j-in. 1:2, 1:3 gypsum plaster Wood lath with J^-in. 1:5, 1:7.5 lime plaster Metal lath (no paper backing) with %-in. 1:2, 1:2 gypsum

plaster Metal lath (no paper backing) with M-in. neat gypsum

plaster Metal lath (no paper backing) with 1-in. neat gypsum

plaster... Metal lath (no paper backing) with %-m. 1:5, 1:7.5 lime

plaster Metal lath (no paper backing) with M-in. Portland cement

plaster Paper-backed metal lath with %-in. 1:2, 1:3 gypsum

plaster

1-in. magnesium oxysulfate woodfiberboard with 3^-in. 1:3, 1:3 gypsum plaster

Limit of protection

510

15

30

10

15

30

15

15

15

30

35

10

10

20

20

5. Fire-Resistance Ratings for Walls and

Partitions With Cem ent-Asbestos Facings

(a) Test Conditions

The fire tests upon which the ratings are based were conducted in substantial accord with

the Standard Specifications for Fire Tests of Building Construction and Materials, ASA

No. A2-1934. (See (a) under section 1, "FireResistance Ratings for Load-Bearing Masomy

Walls", or (a) under section 4, "Fire-Resistance

Ratings for Wood- and Metal-Framed Partitions.")

(b) Source oj Data

The ratings given herein were taken directly

from the results of fire tests conducted at the

National Bureau of Standards.

(c) Firestopping

The actual protection given by a wall or partition construction may be less than the rated

fire resistance because of passage of fire around

its borders. To prevent this occurrence, the

spaces in any wood framing adjoining the wall or partition must be suitably closed or filled, preferably with incombustible material.

(d) Fire-Resistance Ratings

The ratings given in table 34 are for the indicated facings applied to 2- by 4-in. wood studs

of No. 1 Common or better grade, set edgewise,

spaced 16 in. on centers, having wood plates at top and bottom, and stayed transversely with

wood blocking located to form support at the

horizontal joints of the board facings. The

loading is not to be in excess of 360 lb/in. 2 of the net area of the studs. When the cementasbestos boards or shingles are secured by countersunk nails, the holes drilled for the nails

should be 0.02 to 0.03 in. smaller than the nail

head and care should be taken that the nails are driven so as not to injure the cementasbestos material. For the boards in the test partititions, 6d casing nails were found to be the

most suitable, particularly if the heads are to be

countersunk. The weights of mineral-wool

bats per square foot refer to the net area of the

filled space and are to be taken as the minimum.

All ratings are as load-bearing constructions, ex- cept as noted, and the "combustible" designation applies to all on account of the wood

supports.

(e) Facings as Fire-Protective

Wood Framing

Finishes Over

Temperature measurements taken on the

face of the studs during the tests indicate the

effectiveness of the facings in affording protection to combustible members. In conformity

with the test specifications, the limit of protection is assumed to be reached when an average

temperature rise of 250° F above the initial occurs on the face of the wood supports, or a

rise of 325° F at any one thermocouple location.

The protection periods found for this general

type of partition are given in the last column

of table 34.

[ 35
Table 34.

Cement-asbestos facings

"Ulti- Protec- mate tion Facings fire resist- period

for ance wood

period framing

(A) Partitions faced on both sider withfio-in. cement-asbestos board Same as above filled with full-thick mineral-wool bats weighing 1 lb/ft2 4-in. strips of ?s-in. gypsum boards over edges of studs under facings of fte-in. cement-asbestos boards, fill- ing of mineral-wool bats weighing 2 lb/ft2 Same as above rated as nonbearing

%6-in. cement-asbestos boards over %-in. gypsum wall- board

%6-in. cement-asbestos boards over VS-in. gypsum

sheathing Same as above rated as nonbearing

hr min

10

40

1 15

1 30

hr min

5

20

20

(B) Exterior walls faced as indicated

Outside facing of ?4-in. wood sheathing, asbestos felt weighing 14 lb/100 ft 2 and %2-in. cement-asbestos

shingles. Inside facing of ?'i6-in. board consisting of

^fe-in. wood fiber faced with %-m. cement-asbestos. Outside facing to fire Same as above with inside facing to fire Outside facing same as above. Inside facing of 4-in. strips of %-in. gypsum board over the edges of the studs under facing of ?ls-in. cement-asbestos board.

Filled with full-thick mineral-wool bats weighing 1 lb/ft2

. Outside facing to fire Same as above with inside facing to fire Same as above except gypsum board strips were J-S-in. thick and mineral-wool bats weighed \% lb/ft2

. For

fire exposure on either side ... 1 15

20

15

20

15

20

6. FlRE-RESI STANCE RATINGS FOR PREFABRICATED and Built-up Partitions

(a) Test Conditions

The fire tests upon which the ratings are based were conducted in substantial accord

with the Standard Specifications for Fire Tests

of Building Construction and Materials, ASA

No. A2-1934. (See (a) under section 1, "FireResistance Ratings for Load-Bearing Masonry

Walls," or (a) under section 4, "Fire-Resistance

Ratings for Wood- and Metal-Framed Partitions.")

(5) Sources oj Data

Ratings given under (d) in table 35 are based on recommendations of the Forest Products

Laboratory of the U. S. Department of Agriculture. All other ratings are based on fire tests conducted at the National Bureau of Standards

(see BMS71, and Research Paper RP1076).

The ratings are taken directly from the test results without interpolation or extension.

(c) Assembly oj Prefabricated Wood Panels

Joining of panels may be accomplished by the use of wood splines over which the panel

facings are extended, leaving %-in. space

between facings of adjacent panels for calking,

the facings being secured to the splines by

nailing, or battens of suitable thickness may be

nailed over the joints. The assembled partitions may be secured in a similar or equivalent manner to wood plates at the floor and ceiling,

all spaces to be solidly filled. Ratings are based on phenolic resin glue being used for gluing facings to wood frames. If other types

of glue are used for this purpose, the ratings can be taken to apply if the facings are nailed

to the frames in addition to being glued.

(d) Flameproofing

The test results on which the ratings are based indicate that treating the wood with

flameproofing chemicals will not materially

increase the ultimate fire-resistance period.

Hence, the ratings can be taken to apply for either flameproofed or untreated wood. Pending further tests, this should be taken as applying only for the types of treatment and construction details represented in the tests.

(e) Load-Carrying Ability of Built-Up and

Prefabricated Wood or Steel Partitions

No load was applied during the fire tests on which the ratings in tables 35, 36, and 37 are based and, accordingly, they are rated as nonbearing constructions. The condition of the

solid partitions at the end of the test indicated

that at this time they would support at the

most only a small part of a full working load as computed by generally accepted formulas.

Hollow partitions that failed by temperature

rise or flame penetration of the facings had

somewhat greater strength, and mineral-wool

fill in the hollow space further served to protect the studs as load-bearing members. For

hollow partitions the estimated fire-resistance

rating as bearing constructions is in the range

one-half to three-fourths of the rating for nonbearing members, and for the solid partitions

and the steel partition, from one-fourth to one-half of the rating periods given below.

Where the loads actually applied are lower

[36]
than the maximum permitted by accepted

design formulas, the fire endurance under load

will be greater than as estimated above.

Table 35.

Built-up and 'prefabricated wood partitions

all rated as nonbearing, combustible

Partitions

Ultimate

Oreresistance period

(a) Solid partitions of l'Ho by 3!4-in. TAG beaded wood boards nailed

together, the board joints being vertical and staggered

Two board layers Two board layers with asbestos paper weighing 30 lb/100 ft 2 between layers

15

26

(b) Solid panels of 94-in. wood boards, 21 i to 6 in. wide, grooved and

joined with wood splines, nailed together, boards placed vertically with staggered joints except as noted

One board layer. Two board layers. - Three board layers Three board layers with center boards not vertical.

1025

40

35

(c) Solid panels with ?-f«-in. plywood facings glued to 1%-in. solid wood

core of glued T&G construction for both sides and ends of core pieces with T&G rails in the core about 2% ft apart

2H-in.-thick panels.

(d) Hollow panels with facings on both sides of plywood glued to wood

frame. Thickness of framing not less than IK in.

J4-in. plywood faces.

5i-in. plywood faces... )-Hn. plywood faces

5 i-in. plywood faces...

10

1520

25

(e) Hollow panels of plywood, H in. thick on one side and 34 in. thick on

the other side, glued to 2%- by ?4-in. wood studs, set edgewise, and

filled with mineral wool bats weighing 2 lb/ft2 of filled space

3 in. thick panel.

Table 36.

Prefabricated steel partitions rated as nonbearing

Partitions

Hollow panels with 18 gage steel facings spot-welded to steel channels having 3 rows of 4- by Vs-'m. staggered slots in the web, hollow space filled with heat-expanded vermiculite weighing 1.5 lb/ft2 of wall surface, over-all thickness of panel 3 m

Same as above but with vermiculite fill weighing 2 lb/ft2 of wall surface

Ultimate

fire- resistance period

25

30

Table 37.

Partitions of prefabricated reinforced concrete units rated as load-bearing

Partitions

Prefabricated metal-reinforced concrete wall units, separate

units for each face, connected with wood splines and

metal pins, the assembly forming a 5-in. masonry wall with 1-in. faces and 3- by 13-in. continuous vertical air spaces. The rating is for loads not in excess of 2,250 lb/linear ft Same as above with all spaces filled with "nodulated"

mineral wool weighing not less than 10 lb/ft 3

Ultimate

fire- resistance period

7. Fire-Resistance Ratings for Columns

(a) Test Conditions

The fire tests cited below were conducted in

substantial accord with the Standard Specifications for Fire Tests of Building Construction

and Materials, ASA No. A2-1934. The col- umns were tested under working loads corres- ponding approximately with those computed

by commonly accepted formulas, the criterion

of failure being collapse under such load. No

portion of the protection is computed as carrying load, although inevitably some types of

protections will sustain a part of the load,

particularly near failure.

(b) Effect of Plaster

The fire-resistance period for columns having

ratings of less than 2)i hr, from 2% hr to 4 hr,

and 4 hr or more will be increased by at least 1 hr, iy2 hr, and 2 hi", respectively, by the application of % in. of 1 : 3 sanded gypsum or 1 in. of

1:2% portland cement plaster, the latter being

held in place with wire mesh weighing 2 lb/yd2

, the plaster proportions being by weight of

cementing material to that of dry sand. Plaster

may develop more than its normal protective

value if it adds to the stability of the protection

to which it is applied.

(c) Sources oj Data

(1) Timber columns.—Data taken from Fire

tests of building columns, Tech. Pap. BS 15

(1921) T184; and Fire Exposure Tests of

Loaded Timber Columns, Underwriters' Bulletin of Research No. 13, November 1939.

(2) Round cast iron columns.—Data taken

from NBS Tech. Pap. T184.

(3) Steel pipe columns.—Data taken from

NBS Tech. Pap. T184.

(4) Structural steel columns (unprotected).—

Data taken from NBS Tech. Pap. T184.

(5) Structural steel {solid section) partly protected with concrete.—Data taken from NBS

Tech. Pap. T184.

(6) Structural steel {latticed) partly protected

with concrete. —Data taken from NBS Tech.

Pap. T184. Concrete mix not leaner than 1:8

by volume of portland cement to aggregates.

(7) Structural steel solidly protected \oith con- crete.—Data taken from NBS Tech. Pap. T184,

[37]
with due consideration of the influence of mineral composition of aggregates on fire resistance

of concrete, Proc. Am. Soc. Testing Materials

29, pt. 2, 824 (1929). Concrete mix not leaner

than 1:8 by volume of portland cement to aggregates.

(8) Structural steel protected with hollow tile and concrete.—Data taken from NBS Tech. Pap.

T184. Ratings are average values taken from

test results.

(9) Structural steel protected with hollow tile —

Data taken from NBS Tech. Pap. T184.

(10) Structural steel protected with brick.—

Data taken from NBS Tech. Pap. T184.

(11) Structural steel protected with hollow

cinder concrete blocks.—Data taken from "Test

of column for Philadelphia Board of Education," unpublished report, National Bureau of Standards (1938).

(12) Structural steel protected with plaster. —

Data taken from NBS Tech. Pap. T184.

(13) Structural steel protected with gypsum —

Data taken from NBS Tech. Pap. T184; and

Fire tests oj columns protected with gypsum, BS

J. Research 10, 737 (1933) RP563.

(14) Reinforced concrete columns.—Data

taken from NBS Tech. Pap. T184; and Fire

resistance oj concrete columns, Tech. Pap. BS

18, 635 (1924-25) T272. Concrete mix not

leaner than 1 : 6 by volume of portland cement

to aggregates.

(d) Fire-Resistance Ratings

Ratings for various columns are given in tables 38 to 41, inclusive. The ratings for structural steel solidly protected with concrete,

table 39, are based on the test reports cited

with interpolations and extensions made by the

method given in appendix B, section 2(a), to include 6- by 6-in. to 12- by 12-in. structural

steel sections having 2-, 3-, and 4-in. outside

protection. Formula 4 was applied for the

purpose with the following values for the

constant c: For group I aggregates, 0-135; for group II, 0.095; for group III, 0.075; for group

IV, 0.045. The above constants give the fire resistance in hours when D and d are taken in

inches. The higher computed values were

reduced somewhat on account of possible

spalling and fusion effects.

The ratings for reinforced concrete columns,

table 41, have been derived in part from interpolations and extensions made by the method

given in the appendix B, section 2 (b). The

values given under columns (A) were derived

with formula 4 and those under columns (B)

with formula 5. The higher computed values were reduced for the reason indicated above in the case of structural steel protected with

concrete.

It is to be understood that the classifications for the aggregates apply to the coarse aggregate

only. The fine aggregate can be of any type

meeting accepted specifications for use in concrete. Table 38.—Timber columns and unprotected or partly

protected cast iron, steel pipe, and structural steel columns

Type of column

Ultimate

fire-resist- ance period

Timber (long leaf pine or Douglas fir) minimum area 120 in. 2

With unprotected, steel plate cap With unprotected, cast iron cap and pintle. With concrete or protected steel or cast iron cap With %-in. gypsum wallboard over column and over cast iron or steel cap With 1-in. portland cement plaster on wire lath over column

and over cast iron or steel cap, %-m. air space_ W

Round cast iron columns (7 in. outside diameter) minimum thickness

of metal 0.6 in.

Unprotected

Concrete filled, outside unprotected

1 H-in- Portland cement plaster on high ribbed metal lath,

J^-in. broken air space. _ 2-in. concrete (other than siliceous aggregate).

2-in. porous hollow tile, M-m. mortar between tile and

column, outside wire ties.

3

Steel pipe (minimum thickness of metal iMo in.)

7-in. inside diameter, concrete filled, outside unprotected.

8-in. inside diameter, concrete filled, reinforced with four

3 Vi- by 3 Yv by %-in. angles, in fill, outside unprotectedStructural steel, unprotected

Minimum area of steel 10 in. 2 .

Structural steel (solid section) partly protected with concrete

Reentrant space filled, outside unprotected, group I, II, or III aggregates, minimum area of solid materials 36 in. 2

.

.

Same as above, group II or III aggregates, minimum area

of solid materials 64 in. 2 Same as above, group I aggregate, minimum area of solid materials 64 in. 2

Structural steel (lattice section) partly protected with concrete (no ties)

Interior filled, lattice and main members covered, concrete extending to outside of rivets, group II aggregates, mini- mum area of solid material 130 in. 2 Same as above, group I aggregate, minimum area of solid material 130 in. 2 .. - -

38]
Table 39. -Structural steel columns

with concrete

solidly protected

Type "f column and protection

6- by 6-in. steel columns, 2-in. outside

protection

6- by 6-in. steel columns, 3-in. outside

protection

6- by 6-in. steel columns, 4-in. outside

protection

8- by 8-in. steel columns, 2-in. outside

protection

8- by 8-in. steel columns, 3-in. outside

protection

8- by 8-in. steel columns, 4-in. outside

protection

10- by 10-in. steel columns, 2-in. outside protection

10- by 10-in. steel columns, 3-in. outside protection

10- by 10-in. steel columns, 4-in. outside protection. __

12- by 12-in. steel columns, 2-in. outside protection

12- by 12-in. steel columns, 3-in. outside protection

12- by 12-in. steel columns, 4-in. outside protection

Ultimate fire-resistance period.; grouping by aggregates and

ties

5

7

III

m

m

5

3

4

6

4

5

7

IV

Ar

2

3

4

2]4 m

5

3

4

5

Group I includes concrete having calcareous aggregate containing a combined total of not more than 10 percent of quartz, chert, and flint for the coarse aggregate. Group II includes concrete having trap-rock aggregate applied without

metal ties and also concrete having cinder, sandstone, or granite ag- gregate, if held in place with wire mesh or expanded metal having not

larger than 4-in. mesh, weighing not less than 1.7 lb/yd2

, placed not more

than 1 in. from the surface of the concrete. Group III includes concrete having cinder, sandstone, or granite aggre- gate tied with No. 5 gage steel wire, wound spirally over the column

section on a pitch of 8 in., or equivalent ties, and concrete having

siliceous aggregates containing a combined total of 60 percent or more of quartz, chert, and flint, if held in place with wire mesh or expanded

metal having not larger than 4-in. mesh, weighing not less than 1.7 lb/yd2

, placed not more than 1 in. from the surface of the concrete. Group IV includes concrete having siliceous aggregates containing a combined total of 60 percent or more of quartz, chert, and flint, and

tied with No. 5 gage steel wire, wound spirally over the column section on a pitch of 8 in., or equivalent ties.

Table 40.Structural steel columns protected with

hollow tile, brick, cinder block, plaster on metal lath, or gypsum

Mini- Ulti- mum mate Type of column and protection area of fire- solid resist- mate- ance

rial period

Structural steel protected with clay or shale hollow tile

2-, 3-, or 4-in. tile, wire mesh in horizontal joints (two

pieces in each joint placed on opposite sides and at right angles with respect to joints above or below),

flanges covered with mortar or concrete, reentrant space filled with concrete DoDo

Do _ Do- _ Do _ .... Same as above except reentrant space not filled Same as above except with two wythes of 2-in. tile outside, reentrant space filled with tile and mortar Same as above except with outside wire ties instead of mesh in joints _

hr

80

110 2 145

180 3 220 m 225 4 70

250 4

250

Table 40.Structural Heel columns protected with hollow tile, brick, cinder block, plaster on metal lath, or gypsum—Continued.

Type ol column and protection

Mini- mun

area of solid material

Ulti- mate

fire- resist- ance

period

Structural steel protected with brick (clay or shale)

2}i-m. thick reentrant space rilled with brick and

mortar

in.1

180

270

tlT

7

35^-in. thick reentrant space tilled with brick and

mortar

Structural steel protected with hollow cinder concrete blocks

3-in. hollow block, space between block and steel and

reentrant space filled Willi broken block and mortar, %-m. 1: 3 sanded gvpsum plaster 240 7

Structural steel protected with j?£-in. 1:3 sanded gypsum or 1-in. 1:2 Portland cement plaster on wire or metal lath

One layer Two layers with %-in. air space between.

12%

Structural steel protected With gypsum

2-in. solid blocks with wire mesh in horizontal joints,

1-in. mortar on flange, reentrant space filled with

block and mortar Same as above with J^-in. sanded gypsum plaster

2-in. solid blocks with wire mesh in horizontal joints,

1-in. mortar on flange, reentrant space filled with gypsum concrete Same as above with J^-in. sanded gypsum plaster

4-in. solid blocks with wire mesh in horizontal joints,

1-in. mortar on flange, reentrant space filled with

block and mortar Same as above with reentrant space filled with gypsum

concrete

2-in. solid blocks with cramps at horizontal joints, mortar on flange only at horizontal joints, reentrant space not filled Same as above with >^-in. sanded gypsum plaster

3-in. hollow blocks with cramps at horizontal joints, mortar on flange only at horizontal joints, reentrant space not filled Same as above with J^-in. sanded gypsum plaster

2-in. neat fibered gypsum, reentrant space filled, poured solid and reinforced with 4- by 4-in. wire mesh, M-im sanded gypsum plaster...

130

150

130

150

300

300

85

105

95

120

130

2H

5

2M

4

2H

5

Table 41.Reinforced concrete columns

Ultimate fire-resistance period, grouping by aggregates and ties

Type of column

I II III TV

(A) (B) (A) (B) (A) (B) (A) (B)

Reinforced concrete columns With

1}4 in. of concrete outside of re- inforcing steel: Outside diameter of round columns or side of square columns, including outside

protection: Ar hr Ar Ar Ar Ar Ar ftr 12 in 6 4 4 3 2 2 m 14 in 5 5 4 2% 2Vi ,VA

16 in__ 9 6 6 4 5 3% 3 2

18 in. 11 8 5 6 4 m 21 2 20 in 12 9 9 6 7 5 4 3

a Groupings of aggregates and ties are the same as for structural steel columns protected solidly with concrete, the ties to be placed over the

vertical reinforcing bars and the mesh, where required, to be placed within 1 in. from the surface of the column. Under column A working loads are assumed as carried by the area of the column inside of the lines circumscribing the reinforcing steel. Under column B working loads are assumed as carried by the gross area of the column. [39]
8. Fire-Resistance Ratings for Floor

Constructions

(a) Test Conditions

The fire tests upon which the ratings are based were conducted in substantial accord

with the Standard Specifications for Fire Tests

of Building Construction and Materials, ASA

No. A2-1934. This specification contemplates

fire exposure to the under side of the construction and the fire-resistance period is taken to be

reached if: (1) An average temperature rise of 250° F or a maximum rise of 325° F, measured with

thermocouples under asbestos pads, is attained on the unexposed side (upper side) of the

construction.

(2) Passage of heat, flame, or gases hot

enough to ignite cotton waste occurs.

(3) Structural collapse under the design load

occurs. For a full rating the requirements of the hosestream test must be met. Floor constructions

having ratings of less than 1 hr require no

hose-stream test. Those having ratings of 1 hr or more require a hose-stream test after a

fire exposure equal to one-half the time of the

rating, except that for ratings of more than 2

hr the fire exposure before the hose-stream

test need not be of more than 1-hr duration.

Floor constructions involving material which

burns freely during the fire test or continues to burn after the furnace is shut off are rated as "combustible."

Where any information is available on the

resistance of floor constructions to fire from

above, this is given under the respective types.

(6) Source of Data

The results of fire tests conducted at the

National Bureau of Standards were used as a

basis for the ratings given herein. The ratings

in general were taken directly from the test results and represent the lower averages of

results in the case of tests on similar constructions.

(c) Plaster

Measurements of plaster thickness are taken

from the face of the plaster base except that

for metal lath the thickness is measured from

the back of the lath. See section 4, FireResistance Ratings for Wood- and MetalFramed Partitions, for further information

concerning plaster.

(d) Fire-Resistance Ratings for WoodJoist Floors

The ratings given in table 42 are for the indicated ceilings applied to the following construction: Joists of 2- by 10-in. southern pine

or Douglas fir of No. 1 Common or better

grade, subfloor of %-in. wood sheathing, diaphragm of asbestos paper, and finish of tongueand-groove wood flooring. The diaphragm

can be of ordinary building paper if tongueand-groove subflooring is used. The ratings

apply for loadings developing not more than

1,000 lb/in.2 maximum fiber stress in the joists.

The dimensions and spacings of nails given for supporting ceilings are to be taken as the minimum required. Larger nails and closer spacings can be substituted. The perforations in

the gypsum lath are to be of not less than

%-in. diameter, with one perforation for not more than 16 in.2 of lath surface.

All constructions are rated as "combustible" on account of the wood supports and floor boards.

The criteria for the limit of protection given

the wood joists by the ceiling finish are the same as given above (par. 4, a-1) for partition

facings over wood studs.

Table 42.Wood-joist floors

Description of celling

Ulti- mate

fire-re- sistance period

Protection period

for the wood

joists

Exposed wood joists

No ceiling.

Gypsum wallboard, unplastered

Gypsum wallboard H- or Yi-in. thick secured with

lj-i-in. No. 15 gage nails having %e-in. heads, spaced

6 in. centers, covered with asbestos paper applied with paperhangers' paste and finished with casein paint. Gypsum wallboard }^-in. thick secured with l?4-in. No. 12 gage nails having H-in. heads, spaced 6 in. centers, and finished with casein paint Gypsum wallboard l-i-in. thick secured with lH-in. No. 12 gage nails having !4-in. heads and spaced 18

in. centers, covered with asbestos paper applied with

paperhangers' paste and secured with lH-in. No. 15 gage nails having M6-in. heads, and finished with

casein paint (combined spacing of nails, 6 in. on

CGntcrs) Two layers of %-in. gypsum wallboard secured with

lH-in. No. 15 gage nails having Me-in. heads, the combined spacing of the nails being 6 in. on centers..

hr min

15 mm

None

18

20

[40]
Table 42.—Wood-joist floors—Continued

Description of ceiling

Ulti- mate

fire-re- sistance period

Protection period

for the wood

joists

Perforated gypsum lath, :'i in. thick, plastered

Perforated gypsum lath secured with l^t in. No. 13 gage nails having ^6-in. heads spaced 4 in. on centters, H-in. 1:2 sanded gypsum plaster___ Same as above except nailed with l}<s-in. No. 13 gage

nails having %-in. heads and spaced 4 in. on centers.

.

Perforated gypsum lath nailed with 1^-in. No. 13 gage nails having %-in. heads and spaced 4 in. on

centers, joints covered with 3-in. strips of metal lath nailed with l?4-in. No. 12 gage nails having K'-in. heads (2 nails to each joist for strips perpendicular to

joists, and spaced 5 in. on centers for strips over

joists), li-in. 1:2 sanded gypsum plaster.

Two layers of gypsum lath, plastered

One layer of %-in. plain gypsum lath and lower layer of

96-in. perforated gypsum lath (joints broken) nailed with 1 H-in. No. 13 gage nails having Yie-ia. heads and spaced 4 in. on centers, J4-in. l:2sanded gypsum

plaster or )^-in. 1:3 Portland cement plaster.

Metal lath and plaster

The thickness of plaster is to be taken as the average measured from the back of the lath. Metal lath nailed with 1 J4-in. No. 11 gage nails having %-in. heads or 6d common wire nails driven

1 in. and bent over, spaced 6 in. on centers, H-in. sanded gypsum plaster 1:2 for scratch and 1:3 for brown coat. Same as above except nailed with 1 J6-in. No. 11 gage barbed roofers' nails having Jle-in. heads and spaced

6 in. on centers- Either of the above with the lath nailed to joists as given and with additional supports for the lath, placed 27 in. on centers, attached to alternate joists and consisting of two nails driven IK in., 2 in. above bottom on opposite sides of the joists, one loop of No. 18 gage wire slipped over each nail and the ends

of these loops twisted together below the lath Metal lath nailed with V/i-in. No. 11 gage barbed roofers' nails having %6-in. heads and spaced 6 in. on

centers, H-in. Portland cement plaster 1:2 for scratch and 1:3 for brown coat, plus 3 lb of asbestos fiber and

15 lb of hydrated lime per 94-lb bag of cement

Metal lath nailed with 8d, 11 $4 gage barbed box nails

1Yi in. long, driven 1% in. on slant and bent over, spaced 6 in. on centers, 3A-in. sanded gypsum plaster

1:2 for scratch coat and 1:3 for brown coat

12

12

15

10

(e) Fire-Resistance Ratings for Steel-Joist Floors

The ratings given in table 43 apply to the

floor constructions indicated when supported on open-web steel joists, pressed steel joists, or

rolled steel beams, which are not stressed

beyond 18,000 lb/in.2 in flexure for open-web or pressed or light rolled steel joists and 20,000

lb/in.2 for American standard or heavier rolled

beams, and are bridged in accordance with

accepted requirements. The ratio of weight of

Portland cement to that of fine and coarse aggregates combined for the floor slab shall not

be less than 1:6& The plaster for the ceiling

shall be applied on metal lath (expanded metal, woven wire, or paper-backed wire lath) of

appropriate weight for the spacing of the supports. The lath shall be tied to the supports

to give the equivalent of single No. 18-gage

steel-wire ties on 5-in. centers. The thickness

of plaster shall be the depth from the back side

of flat lath and to the back of the flat portion

of ribbed lath. The slab thicknesses are measured from the

top flange of the joists and unless otherwise

indicated are for monolithic poured construction. To obtain the fire-resistance ratings

herein given, the average thickness of the slabs cast in place should be % in. greater than at the

joists. This greater average thickness usually

results from the sag of metal lath forming or the

placing of the more rigid forms under the top

flange of the joists.

Table 43.Steel-joist floors

[All plaster proportions are by dry weight of materials]

Construction

Floor: 2-in. reinforced concrete, or 2-in. precast reinforced gypsum tile. Ceiling: H-in. Portland cement sand plaster 1:2 for scratch and 1 : 3 for brown coat with 15 lb of hydrated

lime and 3 lb of short asbestos fiber per bag of Portland cement, or %-m. sanded gypsum plaster 1 : 2 for scratch coat and 1 : 3 for brown coat.

Floor: 2J£-in. reinforced concrete or 2-in. reinforced gypsum

tile, the latter with M-in. mortar finish. Ceiling: M-in. sanded gypsum plaster 1 : 2 for scratch coat and 1 : 3 for brown coat.

f7oor: 2-in. reinforced concrete, or 2-in. reinforced gypsum

tile, the latter with 54-in. mortar finish. Ceiling: 1-in. neat gypsum plaster or M-in. gypsumvermiculite plaster, ratio of weight of gypsum to fine heat-expanded vermiculite in the range 2 : 1 to 3 : 1.

Floor: 2} 2-in. reinforced concrete, or 2-in. reinforced gyp- sum tile, the latter with J-2-in. mortar finish. Ceiling: 1-rn. neat gypsum plaster or %-in. gypsum-vermiculite plaster, ratio of weight of gypsum to fine heat- expanded vermiculite in the range 2:1 to 3:1.

Floor: 2

JA-in. reinforced concrete, or 2-in. reinforced gyp- sum slabs, the latter with v2-in. mortar finish. Ceiling: l-in. gypsum-vermiculite plaster applied on metal

lath and proportioned in the range 2:1 to 3:1 gypsum o heat-expanded vermiculite by weight.

Floor: 2-in. reinforced concrete, or 2-in. precast reinforced Portland cement concrete or gypsum slabs, the precast

slabs to be finished with top coating of mortar J4-in. thick.

Ceiling: 2-in. precast reinforced gypsum tile, well anchored

into beams with metal ties or clips and covered with

H-in. 1 :3 sanded gypsum plaster.

Ultimate

fire-resist- ance period

Ar

(/) Fire-Resistance Ratingsfor Steel-Plate Floors

The ratings given in table 44 are for the in- dicated finished floors and ceilings applied to

steel construction that provides a steel-plate

base on which the finished flooring may be

applied directly. The ratings are predicated

upon the following conditions:

41 ]
(1) The rolled-steel supporting beams and

the steel-plate base shall not be stressed beyond

20,000 lb/in. 2 in flexure except for formed steel (wide upper flange) construction, in which case

stresses are limited to 16,000 lb/in. 2 The steel- plate base may be designed either as a flexural or suspension member carrying the load between the main supporting members. In either case the portion of the load carried by the concrete or other flooring material can be considered

in the stress determinations as being carried

separately or in combination with the steel plate as a structural member. In the latter case topping material such as concrete must be

properly bonded to the steel plate.

(2) To prevent cracking of concrete flooring, some type of expanded metal or woven wire

should be embedded near the middepth of the

concrete. This rehiforcing should preferably

be welded to the plate.

(3) Plaster for ceilings is to be on metal lath

wired to rods or channels which are clipped or welded to the under side of the steel construction.

All wiring of lath shall be with steel wire not

smaller than 18 gage and spaced not more than

7 in. apart, preferably with double ties for the

higher ratings or for the wider spacings. The

securing of the rods or channels to the steel construction shall be accomplished in a positive manner at least as effective as the following:

Single %6-in. iron rods with 1 in. of their length

bent over the lower flanges of beams with the

rods or channels tied to this clip with 14 gage

iron wire ties. In lieu of the above the plaster

may be on ribbed or reinforced metal lath wired

directly to the clips, the clips being as indicated

above. The weights of metal lath and the

weights and spacing of rods or channels can be

according to usual specifications.

(4) The ratings are based on tests in which

the back of the lath was located within an inch

or two or in contact with the lower flange of the

supporting steel beams, an air space of at least 3 in. being thus formed between the ceiling and

the floor plate. However, the ratings can be

taken to apply for suspended ceilings in which

the back of the lath may be at some distance

below the steel construction, provided the supporting system for the ceiling achieves a

strength at least equivalent to that outlined

under (3).

(5) While the ratings given are based on fire exposure from beneath, tests of this type of

floor construction indicate that with the floors required for these ratings, the resistance to fire exposure from above is fully equal to that herein

given for fire exposure below the floor.

Table 44.

Steel-plate floors

Construction

Ultimate

fire- resistance period Wood floor and plaster ceiling, rated as combustible

Floor: Asbestos paper weighing 14 lb/100 ft^ cemented to

steel deck with waterproof linoleum cement, wood

screeds and % in. wood floor. Ceiling: %-in. sanded gypsum plaster 1:2 for scratch and

1:3 for brown coat.

] hr

\ 1

Concrete floor and plaster ceiling

Floor: 1^-in. 1:2:4 Portland cement concrete.

Ceiling: ^-in. sanded gypsum plaster 1:2 for scratch and

1:3 for brown coat.

t * 72

Floor: 2-in. 1:2:4 portland cement concrete.

Ceiling: %-in. sanded gypsum plaster 1:2 for scratch and

1:3 for brown coat. 1 2

Floor: 2-in. 1:2:4 portland cement concrete.

Ceiling: 1-in portland cement-sand plaster with 10 lb of hydrated lime added for each bag of cement 1:2 for scratch and l:2J-2 for brown coat.

I 2

Floor: 2-in. 1:2:4 portland cement concrete.

Ceiling: l}-2-in. 1:2 sanded gypsum plaster on ribbed metal

lath. | 2H

Floor: 2-in. 1:2:4 portland cement concrete. ; Ceiling: l^s-m. 1:1 sanded gypsum plaster.

Floor: 2J-2-m. 1:2:4 portland cement concrete.

Ceiling: 1-in. 1:2 sanded gypsum plaster. } m

Floor: 2}2-in. 1:2:4 portland cement concrete.

Ceiling: 1-in. neat gypsum plaster, or %-in. gypsum-vermiculite plaster (ratio of weight of gypsum to fine heat-ex- panded vermiculite to be in the range of 2:1 to 3:1).

\ 3

Floor: 2Ji-in. 1:2:4 portland cement, sand, and cinder concrete, plus^-in. 1:23-2 cement-sand finish. Total thickness, 3 in. Ceiling: lj^-in. 1:1 sanded gypsum plaster.

1 3

Floor: V^-m. gas-expanded portland cement-sand concrete, plus j2-in. 1:2} 2 cement-sand finish. Total thickness,

3 in. Ceiling: lj^-in. 1:1 sanded gypsum plaster.

Floor: 2J-£-in. 1:2:4 portland cement concrete.

Ceiling: 1-in. gypsum-verm iculite plaster (ratio of weight

of gypsum to fine heat-expanded vermiculite to he in the range of 2:1 to 3:1).

1 4

Concrete floors and gypsum tile ceiling

Floor: 2-in. 1:2:4 portland cement concrete.

Celling: 2-in. interlocking unreinforced gypsum tile sup- ported on upper face of lower beam flange, J£-in. 1:3 sanded gypsum plaster.

1 2

Floor: 2-in. 1:2:4 portland cement concrete.

Ceiling: 2-in. precast metal-reinforced gypsum tile, J^-in. 1:3 sanded gypsum plaster (tile clipped to channels which

are clipped to lower flange of beams)

.

1 4

(g) Fire-Resistance Ratings for Cellular Steel Floors

The. ratings given in table 45 are for the in- dicated finished floors and ceilings applied in

[42]
the manner noted to the following- construction: Prefabricated units 2 ft wide, with the

length equal to the span, composed of two

pieces of No. 18 gage formed steel welded to- gether to give four longitudinal cells, the depth

being not less than 3 in. and the distance between cells not less than 2 in. For these ratings

the maximum fiber stress in the steel is not to be in excess of 16,000 lb/in2

.

Tabi,e 45.Cellular-steel floors

Construction

Floor: 1:3:6 portland cement, sand, and gravel concrete applied directly to the top of the steel units and lJ4-in. thick at top of cells, plus J^-in. 1:2 }4 cement-sand finish, total thickness at top of cells, 2 in. Ceiling: Plaster on metal lath tied to furring channels se- cured to runner channels hung from the cellular steel panel. The details of the supporting system for the

plaster ceiling are assumed to conform with usual specifications.

(a) With 1-in. neat gypsum plaster, the back of the lath being located 2 in. or more from the under side of the cellular

steel panel

(b) With 1-in. gypsum vermiculite plaster (ratio of weight

of gypsum to fine expanded vermiculite to be in the range

of 2 : 1 to 3 : 1) , the back of the lath being 2 in . or more from the under side of the cellular steel panel

(c) With 1-in., neat gypsum plaster, the back of the lath being located 9 in. or more from the under side of the cellular

steel panel

(d) With 1-in. gypsum vermiculite plaster (ratio of weight

of gypsum to fine expanded vermiculite to be in the range

of 2 :1 to 3 :1), the back of the lath being 9 in. ormore from

the under side of the cellular steel panel

Ultimate

fire- resistance period

g. Fire-Resistance Classification of Roof

Coverings

(a) Basis of Classification

The requirements for roofing materials from

the standpoint of the public interest can be

based on (1) the protection required for the in- dividual building that is covered and (2) the

fire hazard presented by the building with its roofing to the surrounding construction. Building codes have emphasized one or both of these

considerations.

The classification is based largely on the

degree to which the material resists sustained

ignition from flame and flaming brands, the de- gree to which the fire will spread over the

surface and give off dangerous brands, the protection against ignition and sustained flaming of

combustible roof sheathing on which the roofing

is applied, and the protection against exterior

fire exposure given to incombustible roof sheathing and roof construction.

Brand, flame-exposure, and flame-spread

tests are applied to roofings to determine their

properties from the above standpoints. The

lists of acceptable materials include those that

have been subjected to such fire tests. Classes

1 and 2 are parallel with classes A and B of the

Underwriters' Laboratories and class 3 is similar to their class C except that the asphalt

rag-felt roll roofings laid in. single thickness are not included. Class 4 covers the latter type of roofing as well as some wood-shingle constructions.

(b) Sources oj Data

The classifications are based on the results of

fire tests which have been conducted at the

Underwriters' Laboratories and the National

Bureau of Standards. All of the tests on builtup roofings were conducted at the Underwriters'

Laboratories. Information on the weight of

cementing material in built-up roofings was obtained from the old Federal specifications for

the different types of built-up roofing, no

longer issued, and the Navy Department

"Specification for Roofing, Siding, and Sheet

Metal Work; Dampproofing and Membrane

Water-proofing" No. 7Yg, as well as manufacturers' specifications. The weights given rep- resent minima used in good practice.

Of the prepared roofing materials, fire tests of asphalt-rag felt and asphalt-asbestos felt roofings, cement-asbestos shingles, and some

metal roofings and coated wood shingles were

conducted at the Underwriters' Laboratories.

Tests of slate, cement-asbestos shingles; clay

and cement tile; galvanized steel, tinned steel,

copper, and zinc shingles and sheet roofing;

asphalt-saturated asbestos-felt and asphaltsaturated rag-felt roll roofing and shingles, new

and after weathering up to 12 years; and wood

shingles untreated, chemically treated, and

painted, new and after weathering up to 30

years, were conducted at the National Bureau

of Standards.

(c) General Requirements

Class 1 roofing materials shall be effective

against severe fire exposures, shall not carry or communicate fire, afford a relatively high degree

of protection against fire to any combustible

roof deck on which they may be placed, not

[43]
slip from position, possess no flying-brand

hazard, and shall not require frequent repairs

to maintain their fire-protective properties.

Class 2 roofing materials shall be effective

against moderate fire exposures, shall not be

readily flammable or carry or communicate fire. They shall afford a moderate degree of protection to the roof deck, shall not slip from position, shall possess no flying-brand hazard, and

shall require only infrequent repairs in order to maintain the above properties.

Class 8 roof coverings under light fire exposures shall not be readily flammable or carry or communicate fire under such light fire exposures, afford some degree of protection to the

roof deck, shall not slip from position nor

possess any flying-brand hazard, and shall maintain these properties with only occasional

repairs.

Class 4 ro°f coverings present less resistance

to ignition from sources such as flying brands

than the class 3 coverings but give at least a

slight degree of protection to the roof deck. In

burning they will give off flying brands. Their

susceptibility to ignition from brands will in- crease with time in service. As applied by ac- cepted methods they will not slip from position.

Class 5 comprises wood shingles that on ac- count of thickness, length, treatment, coatings,

underlay, or supporting sheathing are not in- cluded in classes 3 or 4. It also includes

very readily ignitable and hazardous roofing

materials, such as light asphalt or tar impregnated paper or straw thatch.

(d) Lists of Acceptable Roof Coverings

The above general requirements are exemplified by the following lists of roof coverings o1 which a sufficient number have been tested to indicate acceptability for the different classes. Pending the establishment of definite per- formance requirements for various classes of roof coverings, additional coverings not included

herein can be classified by comparison under rec- ognized tests with roof coverings herein classified. (1) Built-up Rooj Coverings.—A classifica- tion of built-up roof coverings is given in tables

46 to 48. The roof coverings are assumed to be

applied according to accepted good practice.

The minimum combined weight of bonding and

coating materials required per 100 ft2 of roof

surface, for coverings nailed to deck and coverings held in place by cementing material applied

directly to deck, are given. In the case of roof

coverings nailed to deck, weights are based on

designs which permit the least number of felt layers to be bonded with cementing material.

The weights of felt given are minima.

Roofs surfaced with gravel or slag require not

less than 400 lb of roofing gravel or crushed

stone or 300 lb of crushed slag per 100 ft2 of roof surface.

Table 46.

Class 1 built-up roof coverings

Description

Minimum

weight of ce- menting material per 100 ft3

Roofing

nailed

to deck

Roofing

ce- mented

to deck

Asbestos-felt saturated with asphalt bonded and surfaced with asphalt cement

lb lb (1) 4 layers of 14-lb felt (181b if coated) v.i 60 110. (2) 2 layers of 28-lb felt (each of 2-ply 14-lb felt) 40 70

(3) 1 layer of 35-lb felt (55 lb if coated) and 2 layers of

14-lb felt (18 lb if coated) 60 90

(4) 3 layers of 14-lb felt (18 lb if coated) limited to in- combustible decks ... 40 90

(5) 2 layers of 35-lb felt (55 lb if coated) limited to in- combustible decks. 40 70

Rag-felt saturated with asphalt , bonded with asphalt cement and sur- faced with gravel or slag on asphalt cement

(1) 4 layers of 14-lb felt (2) 1 layer of 28-lb felt and 2 layers of 14-lb felt

(3) 1 layer of 14-lb felt and 2 layers of 20-lb or heavier cap or base sheets _ _ _ (4) 3 layers of 20-lb or heavier cap or base sheets

(5) 3 layers of 14-lb felt. Limited to incombustible decks _ -

100

100

100

100

80

150

130

130 130

130

Asbestos-felt saturated with asphalt and rag-felt saturated with asphalt bonded and surfaced with asphalt cement

(1) 1 layer of 28-lb rag-felt and 2 layers of 14-lb asbestos

felt (18 lb if coated) limited to incombustible

decks 60 90

Asbestos-felt or rag-felt saturated with tar, bonded with tar and surfaced with gravel or slag on tar

(1) 4 layers of 14-lb felt

(2) 3 layers of 14-lb felt. Limited to incombustible decks _ _

120

95

185

160

Rag-felt saturated with asphalt, bonded with asphalt cement and sur- faced with H-in. asphalt impregnated fibrous board applied with

asphalt mastic.

(1) 3 layers of 14-lb felt or other class 3 built-up roofing.. 40 90

[44]
Table 47.

Class 2 built-up roof coverings

Description

Minimum

weight of ce- menting material per 100 ft'

Roofing

nailed

to deck

Roofing

ce- mented

to deck

Asbestos-felt saturated with asphalt, bonded and surfaced with asphalt cement

(1) 3 layers of 14-lb felt (18 lb if coated)

(2) 2 layers of 35-lb felt (55 lb if coated)

(3) 1 layer of 35-lb felt (55 lb if coated) and 1 layer of

14-lb felt (18 lb if coated)

lb 40

40

40

lb 90

70

70

Rag-felt saturated with asphalt, bonded with asphalt cement and sur- faced with gravel or slag on asphalt cement

(1) 3 layers of 14-lb felt.. _ (2) 2 layers of 30-lb or heavier cap or base sheets... ... 8080

130

110

Asbestos-felt or rag-felt saturated with tar, bonded with tar and surfaced with gravel or slag on tar

(1) 3 layers of 14-lb felt. 160

Table 48.Class 3 built-up roof coverings

Description

Rag-felt saturated with asphalt, bonded and surfaced with asphalt cement:

(1) 3 layers of 14-lb felt (2) 1 layer of 28-lb felt and 1 layer of 14-lb felt

(3) 2 layers of 20-lb or heavier cap or base sheets...

_

(4) 2 layers of 14-lb felt and 1 layer 14-lb or heavier cap or base sheet..

Minimum

weight of cementing material per 100

ft'

Roofing

nailed

to deck

40

Roofing

ce- mented

to deck

90

70

70

90

(2) Prepared Roof Coverings.—Prepared roof

coverings are assumed to be applied according

to accepted good practice. Where rag felt is indicated, asbestos felt of equal weight can be

substituted. The coverings are all classified as applied over wood sheating of 1-in. nominal

thickness.

From the standpoint of relative effectiveness

of the different types of wood roof sheathing,

the tongue-and-groove boards gave the best

results in the brand-and-flame tests and the

square-edge sheathing with boards spaced about

Yi in. apart were indicated as better than slat decks of 3-in. strips spaced 5 or more inches on

centers. Accordingly for classifications based on

slat supporting construction, square-edge or tongue-and-groove sheathing can be substituted

and the latter can be substituted fort he squareedge sheathing.

By end lap is meant the overlapping length

of two units, one placed over the other. Head

lap is the distance that the lower of three superimposed units overlaps the upper unit.

Where the coverings are applied over concrete or other masonry roof slabs of 1 in. or greater thickness, the thickness of the roof

covering is not a consideration as far as fire resistance is concerned.

Class 1. Prepared roof coverings

Brick 2% in. thick.

Reinforced portland cement concrete 1 in. thick.

Concrete or clay floor or deck tile 1 in. thick.

Flat or French-type clay or concrete roof tile, % in. thick with \% in. or more end lap and

head lock, spacing body of tile %. in. or more

above roof sheathing, with underlay of asphaltsaturated rag-felt in one or two layers of total

weight not less than 24 lb per 100 ft 2 or one

layer of asphalt-saturated asbestos-felt weighing

not less than 14 lb per 100 ft 2

. Clay or concrete roof tile, Spanish or Mission

pattern, %6 in. thick, 3-in. end lap, same underlay as above.

Slate Yn in. thick, 3-in. head lap.

Cement-asbestos shingles laid American

method, jj{ 6 in. or greater average thickness, 2-in. head lap.

Corrugated sheet steel, 24-gage metal or

heavier, covered on both sides with asbestos

felt weighing not less than 9 lb per 100 ft 2

t cemented to the steel and saturated and coated

with asphalt weighing not less than 18 lb per

100 ft 2 for each side. Sheets are to have not

less than 3-in. side lap and 6-in. end lap. Over

metal roof decks the underlay is not required

from the standpoint of fire resistance.

Asphalt-saturated asbestos sheet roofing, 4-

ply, with an unsaturated asbestos top sheet,

weight not less than 80 lb per 100 ft2 of roof

surface, laid in single thickness with 2-in. end

lap and side edges butted, with 6-in. wide strip

beneath.

45
Class 2. Prepared roof coverings

Cement-asbestos shingles of %6-hx or greater

thickness laid with not less than than 2 in. side, end, or combined side and end lap, according to the French, Dutch, or Scotch method,

with underlay of asphalt-saturated rag-felt in one or two layers of total weight not less than

24 lb per 100 ft 2 or one layer of asphaltsaturated asbestos-felt weighing not less than

14 lb per 100 ft 2

. Asphalt-asbestos smooth surfaced sheet roofing, 3-ply, laid in single thickness, weight not

less than 60 lb per 100 ft 2 of roof surface

with 2-in. end lap and side edges butted, with

6-in. wide strip beneath.

Asphalt-asbestos felt smooth surfaced sheet

roofing, 3-ply, with an unsaturated asbestos top

sheet, weight not less than 55 lb per 100 ft 2 of roof surface, laid in single thickness with

2-in. or more end and side laps.

Asphalt-asbestos felt shingles made of as- bestos felt saturated and coated with asphalt,

surfaced with mineral granules, and weighing

not less than 80 lb per 108 ft2 and as laid on

the roof with 2-in. or more head lap, weight

not less than 180 lb per 100 ft 2 of roof surface.

Asphalt mastic shingles composed of asphalt

and fibrous and granular materials of which not

less than 45 percent by weight is incombustible,

laid with not less than 2-in. head lap, total weight not less than 425 lb per 100 ft2 of roof

surface.

Copper, galvanized iron, or tin-coated iron

standing seam or flat seam sheet roofings, underlaid with 14-lb saturated or unsaturated as- bestos felt or asphalt-saturated rag-felt in one

or two layers of total weight not less than 24

lb per 100 ft2 of roof surface.

Copper or galvanized iron tile or shingle

pattern roofings with same underlay as above.

Class 3. Prepared roof coverings

Copper, galvanized iron, or tin-coated standing-seam or flat-seam sheet roofing either without underlay or with underlay of rosin-sized

paper.

Copper or galvanized iron tile or shinglepattern roofings without underlay or with

underlay of rosin-sized paper.

Asphalt rag-felt individual or strip shingles

made of rag-felt saturated and coated with as- phalt, surfaced with mineral granules and

weighing not less than 80 lb per 108 ft2 and as

laid on the roof with 2-in. or more head lap,

weight not less than 180 lb per 100 ft2 of roof

surface. Asphalt-asbestos felt-roll roofing surfaced

with mineral granules and laid in single thick- ness with 2-in. or more side and end lap, weight

not less than 85 lb per 100 ft 2 of roof surface.

Asphalt-asbestos felt smooth-surfaced sheet

or roll roofing laid in single thickness with 2-in. or more end and side lap, weight not less than

50 lb per 100 ft2 of roof surface.

Zinc sheet or shingle roofings with underlay

of 24-lb asphalt-saturated rag-felt in one or two

thicknesses or 14-lb unsaturated or asphaltsaturated asbestos felt. Wood shingles with butt thickness not less than % in. laid with not less than 6-in. head lap,

coated on bottom with, asphalt emulsion weighing not less than 4 lb per 100 ft2 of roof surface

except for upper 2 in., and on top and three

edges with asphalt weighing not less than 60

lb per 100 ft2 of roof surface, into which are embedded granules of crushed slate weighing not

less than 100 lb per 100 ft2 of roof surface.

Shingles are to be laid over slat or close %-in. wood sheathing.

Class 4. Roof coverings

Asphalt rag-felt mineral-surfaced roll roofing

laid in single thickness with 2-in. or more end

and side laps, weight not less than 75 lb per 100

ft2 of roof surface.

Asphalt rag-felt smooth-surfaced roll roofing

laid in single thickness with 2-in. or more end

and side laps, weight not less than 35 lb per

100 ft2 of roof surface.

Wood shingles of not less than %-in. butt

thickness chemically treated under pressure

with double treatment of sodium borate, and

zinc chloride with evacuation and drying between treatments laid with 6-in. or more head

lap.

Edge-grain red-cedar, redwood, and No. 1 pine shingles, %6-im butt thickness, 18 in. long, laid with 5-in. weather exposure on %-in.

square-edge wood sheathing with boards spaced

not more than % in. apart.

[46]
Edge-grain red-cedar and redwood shingles,

%-in. butt thickness, 16 in. long, laid with 5-in. weather exposure on %-in. tongue-and-groove

wood sheathing.

Edge-grain red-cedar and redwood shingles,

%-in. butt thickness, 16 in. long laid with 5-in. weather exposure on %-in. square-edge wood

sheathing with boards spaced not more than

% in. apart and asphalt or tar-saturated rag

felt between shingles and sheathing.

Wood shingles of any species %-in. or greater

butt thickness, 16-m. or greater length, laid

with not less than 6-in. head lap on %-in.

square-edge or tongue-and-groove wood sheathing, spaces between boards not more than % in. and underlay between boards and shingles of

asphalt-saturated rag-felt in one or two layers

weighing not less than 24 lb per 100 ft2 or

asphalt-saturated asbestos-felt weighing not

less than 14 lb per 100 ft2

. Red-cedar, redwood, or No. 1 pine shingles,

butt thickness not less than % in., 16-in. or greater length, laid with not less than 6-in. head lap on %-in. square-edge or tongue-andgroove wood sheathing, space between boards

not more than % in., shingles before application

to be dipped to within 2 in. of the top in mineral

oxide paint thinned so that the weight of

pigment is not less than 30 percent of the weight

of the prepared paint, and a brush coat of the

unthinned paint applied over the exposed length

after application on the roof.

Class 5. Roof coverings

Roof coverings possessing greater fire hazard

than those included in class 4.

[47]
APPENDIX A. SUMMARY OF RESTRICTIONS AND LIMITATIONS IN SIX TYPICAL BUILDING CODES BASED ON TYPES OF CONSTRUCTION

This study is based upon an analysis of building codes

to determine the nature and extent of the restrictions imposed by them according to types of construction. The following codes were used: New York City, 1938; Boston, (Proposed, 1938);

Minneapolis, 1935;

Atlanta, 1924; Denver, 1935;

Seattle, 1937. The restrictions in each of the codes were studied

tinder the following general headings supplemented

with a brief discussion:

I. Classifications.

II. Location with respect to fire zones.

III. Permissible spacing from adjacent construction or property lines. IV. Permissible heights and areas of buildings. V. Permissible materials. VI. Required degrees of fire resistance of struc- tural members.

VII. Permissible occupancies.

VIII. Discussion. The study covers substantially the requirements of the codes on the topics under consideration, but necessarily presented in abbreviated form rather than in the

original wording. For information regarding specific cases reference should be made directly to the codes. For convenience, the classifications of construction by type and occupancy are included in the study at the beginning. When encountered later in the detailed requirements, they may be identified by turning back to the first section. Permissible heights and areas are given as combined limitations where they are so expressed in the codes. These requirements are presented as typical of those

applied in building codes of American cities at the present time. A discussion thereof in relation to the

classifications of building construction presented in this report is given at the end of this summary.

I. CLASSIFICATIONS

1. New Yokk

(a) Classification of Structures by Type of Construction

Class 1. Fireproof structures. Class 2. Fire-protected structures. Class 3. Nonfireproof structures.

Class 4. Wood frame structures. Class 5. Metal structures. Class 6. Heavy timber structures.

(b) Classification by Occupancy

Public Buildings.—Structures for civic, political, educational, religious, or recreational purposes, or in which persons are harbored for medical, charitable or other care or treatment. Residence Buildings.—Structures in which sleeping

accommodations are provided (unless otherwise classed

as public buildings), including multiple dwellings.

Commercial Buildings.—Structures which are neither public nor residence buildings, but which include office buildings, factories, sales rooms, markets, restaurants, warehouses, garages, etc.

2. Boston

(a) Types of Construction Type I. Fireproof.

Type II. Semifireproof.

Type III. Heavy timber and masonry. Type IV. Light wood and masonry. Type V. Metal frame. Type VI. Wooden frame.

(b) Occupancies Classified

Group A. Theaters. Group B. Halls. Group C. Schools. Group D. Hospitals and detention buildings.

Group E. Commercial buildings of hazardous occu- pancy. Group F. Offices and commercial buildings.

Group G. Commercial buildings of nonhazardous occu- pancy. Group H. Dwellings, large. Group I. Dwellings, small. Group J. Miscellaneous structures.

3. Minneapolis

(a) Types of Construction Type 1. Fireproof.

Type 2. Slow burning.

Type 3. Skeleton and all-steel. Type 4. Ordinary.

Type 5. Frame.

[48]
(b) Classification of Buildings

Class A-l.—Bakeries, chemical works, crane sheds,

flour mills, foundries, ice-storage houses,

laundries, machine shops, manufacturing

buildings, power houses, sheds, warehouses, wholesale stores, woodworking

shops.

Class A-2.- Baths, business colleges, department

stores, markets, office buildings, places of assembly for not over 100. public conveni- ence stations, recreation buildings, res- taurants, retail stores, telephone ex- changes.

Class B-l. —Garages, motorboat houses, hangars,

paint shops, enameling shops, rag shops,

buildings for the manufacture, storage, use or sale of inflammable liquids and

other inflammable substances, including

calcium carbide. Class B-2.— Dry-cleaning establishments, buildings

used for storage or manufacture of celluloids, buildings for storage of explosives

and for generating acetylene. Class B-3.— Stables. Class C. — Public buildings: Armories, auditoriums,

churches, administrative buildings, court- houses, dance halls, post offices, schools,

etc. Class D.—Theaters.

Class E-l.— Multiple dwellings, hotels, lodging houses,

dormitories, monasteries, convents, boarding schools, clubhouses, more than 10

sleeping rooms.

Class E-2.—Hospitals, sanitariums. Class E-3.—Prisons, reformatories, jails, asylums.

Class F.—Single and two-family dwellings, lodging

houses, dormitories, monasteries, not more

than 10 sleeping rooms.

4. Atlanta

(a) Classification of Buildings by Construction

I. Frame construction.

II. Non-fire-resistive construction.

a. Ordinary construction.

b. Mill construction.

III. Fire-resistive construction.

(b) Classification of Buildings by Occupancy

I. Public Buildings. Class A.—Armories, asylums, bath houses (with

sleeping accommodations other than those re- quired for janitor), city halls, colleges, court houses, detention buildings, police stations, hospitals,

libraries, museums, nurseries, railway passenger

stations, schools and theaters. Class B.—Amusement halls, churches, exhibition

buildings, lodge rooms, public halls.

II. Residence Buildings. Class C.—Bachelor apartments, club houses and

studios with more than 15 sleeping rooms, dormitories, hotels, and lodging houses. Class D.—Dwellings, apartment houses, and all other residence buildings not specified in Class C.

III. Business Buildings. Class E.—Factories, lofts, office buildings, printing houses, restaurants, stores, warehouses, and

workshops.

Class F.—Car barns, foundries, light and power

plants, railroad freight stations, ice houses; special

industry buildings such as coffee roasters, cooper- age shops, dry-cleaning establishments, grain

elevators, ice-making plants, laboratories, malt

houses, oil houses, oil refineries, refrigerating

plants, rendering plants, soap factories, sugar

refineries, smoke houses, slaughter houses, wharf

buildings, garages accommodating more than three

cars.

5. Denver

(o) Types of Construction Type I. Fire-resistive construction. Type II. Heavy timber construction. Type III. Ordinary masonry construction. Type IV. Metal frame construction. Type V. Wood frame construction.

(b) Occupancy Classification Group A-l.—Major theaters with stage loft and equip- ment.

A-2.—-Moving picture theaters seating 1,000 or more.

A-3.—Places of public assemblage seating 1,000 or more in any one room. Group B-l.—Theaters seating less than 1,000. B-2. —Places of public assemblage seating less than 1,000 in any one room. Group C.— Public and parochial schools. Group D-l.—Jails, prisons, reformatories, asylums.

D-2.—Hospitals, sanitariums, orphanages, nurseries accommodating more than 6 patients.

Group E-l.—Public garages, gasoline stations, spray

paint shops. E-2.—Planing mills, box factories, woodworking

and mattress factories. E-3.—Storage of highly inflammable or explosive

materials. Group F—1. —Wholesale and retail stores, office buildings, restaurants, undertaking parlors,

printing plants, police and fire stations. F-2.—Factories and workshops using materials not highly inflammable or explosive. F-3.—Storage and sales rooms for combustible

goods.

Group G-l.—-Ice plants, power plants, pumping plants, cold storage, creameries. G-2.—-Factories and workshops using incombustible or non-explosive materials.

[49]
Group G-3.—Storage and sales rooms for incombustible or non-explosive goods.

Group H-l.—Hotels, apartment houses, dormitories,

lodging houses. H-2.—Convents, monasteries, accommodating

10 or more. Group I.— Dwellings.

Group J-l.—Private garages.

J-2.—Accessory buildings and structures such

as sheds, fences, water tanks, towers.

J-3.—Stadiums, reviewing stands, amusement

park structures.

6. Seattle

(a) Types of Constrvction There shall be five general classes of buildings as follows: Fireproof, steel joist, mill, ordinary masonry,

frame, and such other special classes as are elsewhere

herein permitted for special uses.

(6) Occupancy Classification No occupancy classifications are given.

II. LOCATION WITH RESPECT TO FIRE ZONES

1. Number of Zones, Including an Unrestricted

Area

New York 3 Boston 3 Minneapolis 3 Atlanta 2 Denver 4

Seattle 4

2. Restrictions and Limitations

(a) New York

Frame construction forbidden within fire limits. With certain limitations frame residences occupied

by not more than two families, and one-story stables and garages 600 ft 2 or less in area on the same lot or

plot, are permitted outside fire limits. In the Borough of Richmond, frame structures of two stories in height, not over 3,000 ft 2 in area, are permitted for business purposes other than garages, motor-vehicle repair shops, or gasoline service stations. Certain other frame structures are permitted outside the fire limits provided they are not used for industrial or commercial purposes or as a place of public assembly, and do not exceed 40 ft or three stories and base- ment in height, or 5,500 ft 2 in area.

(b) Boston Wooden frame construction is prohibited within

first fire zone. Wooden frame dwellings for one or two families are permitted in second fire zone. Garages for more than four cars in the first and

second fire zones shall be of fireproof or semifireproof

construction and if more than one story in height shall be of fireproof construction. Metal-frame buildings for use as garages are prohibited in the first fire zone. In the second fire zone, metal-frame buildings for use as garages are per- mitted if one story in height and not more than 600 ft 2 in area. Schools in the first and second fire zones shall be of fireproof or semifireproof construction. Wooden frame buildings not over 27 ft high on

wharves, and for the storage and handling of coal or grain in bulk, are permitted in the first and second

fire zones if the exteriors are covered with slate, tile, sheet metal, or other equally fire-resistive materials.

(c) Minneapolis

Within the Fireproof District, one-story buildings of slow-burning or ordinary construction, or skeleton and

all-steel construction when having masonry exterior

walls, and one-story sheds of all-steel construction not over 400 ft 2 in area or 12 ft high may be erected. All other construction in the Fireproof District is required

to be fireproof.

Within the fire limits, fireproof, slow-burning, skele- ton and all-steel, and ordinary constructions are permitted. Masonry exterior walls are required.

(d) Atlanta No frame building except temporary buildings may

be erected within the fire limits.

(e) Denver Wood-frame construction is prohibited in fire zone? Nos. 1, 2, and 3. Ordinary masonry and metal-frame constructions in

fire zone No. 1 are limited to 400 ft 2 in area and one

story or 20 ft in height.

Temporary structures, such as reviewing stands, are permitted in fire zones Nos. 1 and 2. In fire zone No. 3 frame sheds and chicken houses

are permitted.

There are no restrictions in fire zone No. 4.

(/) Seattle

Buildings in the First Building District are required

to be of fireproof, steel-joist, or mill construction. Ordinary masonr.v construction not higher than one

story is permitted.

The requirements for the Second Building District are the same as those for the First Building District except that ordinary masonry construction may be two stories high. In the Third Building District ordinary masonry

construction may be four stories high. Frame resi- dences of two stories or other frame buildings of one

stor}' if roofed with shingles or of three stories if roofed with three-ply roofing or roofing as for mill buildings are permitted.

There are no restrictions in the Fourth Building

District.

[50]
III. PERMISSIBLE SPACING FROM ADJACENT

CONSTRUCTION OR PROPERTY LINES

1. New York

The restrictions given below apply to structures located outside of fire limits: Frame residence, not more than two families, eight

livable rooms per family, when covering 80 percent or

less of the area of the lot: Distances between buildings across side lot lines, 6 ft. Distance from a side lot line, 2 ft. Four double dwellings with party wall: Distance from opposite side lot line, 4 ft. When width of plot is 30 ft or less, single-family

dwelling:

Distance from lot line on one side, 3 ft. Distance from other lot line if not contiguous with

building on adjoining lot, 2 ft. Frame residence, maximum 10 livable rooms per family, when covering not more than 50 percent of the area

of the lot and 60 percent of the width of the lot: Distance from nearest lot line, 25 ft. Frame residence, maximum 12 livable rooms per

family, when not covering more than 50 percent of the width of the lot: Distance from nearest lot line, 50 ft. One-story stables or garages, 600 ft2 or less in area, 15

ft or less in height; on same plot with one- or twofamily residence structures: Frame.—Distance from lot line, 3 ft. Masonry exterior walls, masonry-veneered or stud

spaces filled: Distance from lot line may be less than 3 ft. Frame business structures in the Borough of Richmond

other than garages, motor vehicle repair shops, or gasoline stations, not over 2 stories in height or 300 ft2

in area or 80 percent of width of lot: Distance from side lot line, 4 ft.

Other frame structures, except commercial, industrial, or places of assembly:

Distance from nearest boundary line, 30 ft. Distance from nearest other structure between it and boundary line, 30 ft. Frame structures, except as otherwise provided:

Clearance from other frame structures on same

plot, 6 ft. Frame structures, used for manufacturing purposes or

for storage of inflammable materials: Distance from lot line, 15 ft. Other business structures of class 5: Distance from lot line, 4 ft.

2. Boston

Halls, Schools, Hospitals, Detention Buildings, Commercial Buildings, Hazardous Occupancies:

Exterior walls less than 5 ft from property line are required to be of 4-hr fire-resistive construction. Exterior walls more than 5 ft but less than 10 ft from property line are required to be of 2-hr

fire-resistive construction.

Office and Commercial Buildings, Commercial Buildngs of Nonhazardous Occupancy:

Large dwellings: Exterior walls less than 10 ft from property

line are required to be of 2-hr fire-resistive construction. Small dwellings: Exterior walls less than 5 ft from a property

line are required to be of 2-hr fire-resistive construction. Miscellaneous Structures: Exterior walls less than 5 ft from a property line or less than 10 ft from another building on the same lot are required to be of 1-hr fire-resistive construction; less than 3 ft from a property line or less than 6 ft from another building on the same lot are required to be of 2-hr fire-resistive construction.

3. Minneaiolis

Exterior walls of Class A buildings required to be of masonry if nearer than 5 ft to property line or 10 ft to another building on the same property. (Class A

includes shops, warehouses, stores, office buildings, and

certain places of assembly.) Exterior walls of Class B-l and B-3 buildings re- quired to be of masonry if within 10 ft of property line or other building on the same property.

No Class B-2 buildings shall be built less than 10 ft from property line or any other building on the same

property.

Dry-cleaning establishments are required to be not

less than 15 ft from any other building on the same

premises and from any property line. No private garage shall be erected within 15 ft of any Class E—1 building (multiple dwellings, hotels, etc.) without permit from the City Council. Walls of garages are required to be of masonry if within 4 ft of any dwelling already erected or within 1

ft of the side lot line. Double private garages may be

erected on the lot line by mutual consent without

masonry separating walls. Airplane hangars may be of frame construction when

40 ft from any adjacent property line or other building

and 20 ft from any other hangar. Walls of Class C (Public) buildings are required to be of masonry if nearer than 5 ft from a property line or other building on the same property.

Class D (Theaters) No applicable requirement.

Sanitariums (Included in Class E-2) one story, 15 ft

in height may be of frame construction if at least 5 ft from any property line or 10 ft from any other frame

building. Walls of Class F buildings are required to be of

[51 ]
masonry if nearer than 3 ft from any property line or any other building on the same property. (Class F

includes dwellings and lodging houses, dormitories, etc. of not more than 10 sleeping rooms.)

Coal pockets, etc., may be of wood if not less than

10 ft from any property line. Gas holders are required to be 100 ft from any

private property held under separate ownership.

Grandstands of wood may not be closer than 10 ft to property line or 20 ft from other frame buildings. Roller coasters of wood are required to be at least 20

ft from property line or other frame structures on the same property. If steel or concrete, not limited as to

location. Other amusement devices of wood shall not be nearer than 20 ft to adjacent property lines.

4. Atlanta

Frame buildings of Class F (various industrial buildings) and frame buildings of other classes exceeding 5,000 ft2 without sprinklers are required to be 35

ft from side or rear lot lines; if the area exceeds 7,500

ft2

, 100 ft from side or rear lot lines. The minimum permissible distance of a frame build- ing from a lot line is 3 ft and from another building on

the same lot, 10 ft. These distances may be reduced

to 3 ft and 5 ft, respectively, if the spaces between the studs are properly filled and the walls protected as

required.

If the adjacent walls of two buildings have no openings, and are protected in the prescribed manner, there

is no limitation as to distance between them.

5. Denveb

Walls of Group E buildings are required to be of masonry if within 10 ft from adjacent property lines.

(Group E includes public garages, shops and factories working with inflammable materials, and places storing

inflammable or explosive materials.) Exterior walls of Group F buildings are required to be of masonry if within 4 ft from adjacent property

lines. (Group F includes stores, office buildings,

factories, and storage places for combustible goods.)

Location with reference to property lines of buildings

of Group I (private dwellings) is governed only by

zoning ordinances.

6. Seattle

Frame residences are required to be 18 in. from the

lot lines of adjacent property.

Frame buildings other than residences are required

to be 3 ft from the lot lines of adjacent property.

These restrictions are removed if the walls are of

fireproof material or otherwise built as required by the

code. Frame buildings not over 400 ft2 in area may, under

certain conditions, be constructed up to the lot line. Walls of incombustible service stations in the First and Second Building Districts are required to be of masonry if nearer than 6 ft from adjacent property

lines. Incombustible shelters on auto parking lots in the

First and Second Building Districts are required to be

3 ft from the lot lines of adjacent property.

IV. PERMISSIBLE HEIGHTS AND AREAS OF

BUILDINGS

1. New York

The maximum height and area limits of buildings as applied in the New York City building code are given

in table 49, but subject to the following qualifications.

Table 49.Maximum heights and areas of buildings, New York City building code

Use classification

(1) Public >»_ (churches only)

(2) Public-

(other than churches, hospitals, asylums and places of incarceration or amusement)

Construction classification

Class I, Fireproof

Height Area

Class II, Fire-protected

Height

ft Stories

Area Street fronts

No.

Class III, Nonfireproof

Height

ft Stories

Area

ft1

Street

fronts

No.

(3) Public —

(other than (1) and (2))_ Unlimited.

(4) Commercial

(other than garages, motor vehicle repair, shops and gasoline selling stations)

(5) Garages, motor vehicle repair shops and

gasoline selling stations.

.do.

Unlimited.

-do.

.do. .do.

(6) Residence- _do. -do. 100

100

100

7, 500

12, 000

15, 000

7,500

12, 000

15, 000

10, 000

14, 500

17, 500

7, 500

12, 000

15, 000

12, 000

15, 000

20, 000

20 5,000

7, 500

12, 000

15, 000

10, 000

14, 500 17,500

7, 500

12, 000

15,000

3, 000

See under Class VI. 52
Table 49.

Maximum heights and areas of buildings, New York City building code—Continued

Use classification

(l) Public a (churches only)

(2) Public

(other than churches, hospitals, asylums and places of incarceration or amuse- ment)

(3) Public

(other than (1) and (2))_

(4) Commercial

(other than garages, motor vehicle repair shops and gasoline selling stations)

(5) Garages, motor vehicle repair shops and

gasoline selling stations

(6) Residence

Construction classification

Class IV, Wood frame

Height

Stories

b 2

3

Area

ft'

GOO

2,500

(single family occu- pancy).

Class V, Metal Class VI, Heavy timber

Height

30

Stories

Height

15,000

75

Stories2

2

Area

IP

ft, ouo

8, 000

6, 000

8, 00(1

6, 000

7, 500

12, 000

15. 000

10, 000

14, 500

17, 500

10, 000

15, 000

18, 000

3, 000

SI reel fronts

No.

1 2 or 3

1

2 or 3

• Sec under Class VI.

b t'noccupied attic permitted.

The limits of area for business and garage structures

(except Class V Metal structures) may be increased

100 percent when approved sprinkler S3r stems are

installed. Class II, Class III, and Class VI, business and garage

structures of greater total area may be constructed,

provided they are divided by fire walls into areas within the tabular limits. Public buildings of Class III construction, whose

tabular height limitation is 20 ft, may be erected to a

height of 35 ft if having only one occupied story. Class III residence structures of greater area than

3,000 ft 2 may be constructed provided they are divided

into units of area of 3,000 ft 2 or less, by walls or parti- tions having a fire-resistance rating of at least 3 hr. Coal pockets and grain elevators, within the fire limits, shall be Class I Fireproof structures, or Class

II Fire-protected structures. Class VI Heavy timber construction or structures used exclusively for the storage or handling of building construction materials may, in the discretion of the Superintendent, exceed 40 ft or 3 stories in height.

2. Boston

The permissible heights and areas of buildings ac- cording to the 1938 proposed code are given in table

50, subject to the following qualifications and further

restrictions.

Buildings on wooden wharves shall not exceed 20,000

ft 2 in area. Group B.—The maximum area provided may be

increased 50 percent if the entire floor area is protected

by automatic sprinklers.

Group C.—Same as Group B. Group D.—Division 1. Jails, prisons, reformatories and similar buildings. Division 2. Hospitals, sanitariums, or- phanages, etc. Division 1 buildings shall be of Type I throughout.

The ceilings and partitions of Division 2 buildings more than one story in height shall be of not less than

1-hr fire-resistive construction, and the first floor of such buildings more than two stories in height shall be

of Type I construction. The basements, cellars, store rooms, corridors, and

stairways of Group D buildings of other than Type I or Type II construction shall be protected by automatic

sprinklers.

Group E.—Division 1. Garages of more than six cars capacity and hangars.

Division 2. Planing mills, box factories, wood-working plants, mattress factories, paint shops,

dry-cleaning plants. Division 3. Buildings for the storage of hazardous, highly flammable,

or explosive material or liq- uids.

53
>

'

i

1

!

i£

Area

'£ 2 2, 2SS 1 ;g o o goo ; lio" "O" «" cc-*uf ! 3,

000 4.000

5,000 3,

000 4.

000

5,000 ;SS88

Height

Stories

! <M 1 eo CO CN <N

is? s s 8°° i i i iggg !

i i ! i issss

I

I

Area 5, ill 111 I is s ^ i

000

'01

000 '8

000 '9 10,

000

12,

000

14,

000 Uiii

Height I

§ ss is sss issss i issss ;

:

IV

Light

wood

and

masonry

Area e, iiiiiiiiiiiiiiiiiiiiiiiiiiiii

Height

Stories

CM

«,

III

Heavy

timber

and

masonry

Area «. 17,

000

20,

000

17,

000

20,

000

12,

000

18.

000 8,

000

10,

000

12,

000 : ;§§§

!

; i-s2 i ills i i jjfSfSf i

j

8,

000 8.000

10,

000

12

00060i000

Height

Stories

i CO CO CO ' i coco co !

i r

mnr

«. iKKiS

i i

! H .1

Area Ci 18,

ooo

24,000 18,

000

24,

000

17,

000

20,

000 8,000

10,

000

12,

000

10,

000

12,

000

15,

000

15,

000

18,

000

20,

000

12,

000

12.

000

15,

000

15,

000

120,

000

Height

Stories

i r>- r~ i i ! oo^ i~ c<i

«. igsg ; : issg 88RSS

Area «. i

10,000 15,000 20,000

i i i i

lunlimited..

'p i

Height

/< |

Stories

Unlimited.

... 222 ;

sis

Sides sible

Types

of

buildings

A,

theatres

d,

nans

C,

schools

_

..

D,

hospitals,

etc

E,

commercial,

hazardous

F,

offices

and

commercial

buildings

Q,

commercial,

nonhazardous

H,

dwellings,

large.

I,

dwellings,

small

J,

miscellaneous

amusement

F,

buildings

on

wharves.

[ 54]
The limits in area shall not apply to buildings one

story high of Group E Division 1 of Type I construction. These may be 15,000, 20,000 and 25,000 ft 2 for one, two, and three sides accessible, respectively.

Every unit of Group E occupancy higher than two

stories or having an aggregate floor area greater than

10,000 ft 2 shall be equipped throughout with auto- matic sprinklers.

Group F.—Division 1. Office buildings, restaurants,

police and fire stations, museums, and libraries. Division 2. Wholesale and retail stores, printing plants, factories and

work shops using materials not highly flammable.

Division 3. Buildings for storage and sale

of goods not highly flam- mable, stables and buildings not on wharves, for storing or handling transient freight. Division 4. Wharf buildings for storage

and handling of transient

freight.

Group F.—Buildings of Divisions 2 and 3, six or more stories in height shall be equipped with automatic

sprinklers.

The maximum areas for buildings of Division 1, and

for buildings of Divisions 2 and 3 less than six stories

in height may be increased fifty percent if the entire

floor area is protected by automatic sprinklers.

Group J. —The maximum areas provided may be

increased 50 percent if the entire floor area is protected

by automatic sprinklers.

3. Minneapolis

(a) Height Limitations Type 1. Fireproof.—This type of construction shall not be limited in height.

Type 2. Slow-Burning.—Limited to six stories, 75

ft. or less in height and not permitted in Fireproof

District except for special cases noted in the code. Type 3. Skeleton and All-Steel.—Limited to one

story and one mezzanine or 75 ft except when roof

purlins or roof boards are of wood, in which case such

buildings shall not exceed 45 ft. Not permitted in Fireproof District except for special cases noted in the

code. Permitted in fire limits when interior walls are

of masonry and buildings are limited in area and located on a lot as given under class of building.

Type 4- Ordinary.—Limited to four stories, 55 ft. Not permitted in Fireproof District when exceeding one story. Type 5. Frame.—Limited in height to two stories and attic or 35 ft. Not permitted in Fireproof District or fire limits. Exceptions.—Buildings not exceeding one story in height of Types 2 or 4, and of Type 3 when having

masonry exterior walls, may be constructed in the

Fireproof District.

Class A buildings shall be built of one of the following

types of construction:

If not over one story or 20 ft, of any type.

If not over four stories or 55 ft, of Types I, 2, or 4. If not over six stories or 75 ft, of Types 1 or 2. If over six stories or 75 ft, of Type 1. Class A-2 buildings may be built of Type 5 construction if not over two stories or 25-ft height.

(b) Area or Combined Height and Area Limitations

General area limitations are given in table 51, which

however, are qualified by building height and occu- pancy as indicated below.

Table 51.

General height and area limitations, Minneapolis code

Type of construction

Type 1 ...

Type 2...

Type3_-.

Type 4 .

Type 5 ..

Number of stories

Maximum floor area

story

stories or over When sprinklered

.

story When sprinklered

stories or over When sprinklered

.

story and mezzanine - When sprinklered. story When sprinklered.

stories or over When sprinkleredstory. _ __ When sprinklered.

stories or over When sprinklered.

One

streets

ft 1 No limit

30, 000

50, 000

20, 000

33, 000

12, 000

20, 000

15, 000

25, 000

12, 000

20, 000

7,500

12, 500 5,000 8,500

3, 000

5,000

Two

streets

ft40,000

66, 000

25, 000

42, 000

14, 000

24. 000

18,000

30, 000

15, 000

25, 000

10,000

17, 000

7, 000

11, 750 4,000

6, 750

Three

streets

55. 000

83, 000

30, 000

50, 000

16, 000

27, 000

20, 000

34, 000

18, 000

30, 000

12, 500

21, 000

9,000

15, 000

5,000 8,500

All Class A buildings except office buildings of Type 1 shall be divided into areas not exceeding those given

in table 51. Buildings of Types 1 and 3 for storage or manufacture

of incombustible materials may be unlimited in area. Class B buildings shall be constructed of one of the

following types of construction: Sub-Class B-l

If not over one story or 20 ft, 600 ft 2

, any type.

If not over one story or 20 ft, over 600 ft 2

, types 1, 2, 3, or 4. If not over two stories or 30 ft, Types 1 or 2. If over two stories or 30 ft, Type 1. Airplane hangars may be Type 5. The height may

be more than 20 ft but not more than 30 ft. Area. 10,000 ft 2

; if sprinklered, 25,000 ft 2

. Class B-l buildings shall be divided into areas not

exceeding those for class A.

Class B-2 buildings shall be Type 1. Class B—2 buildings shall be divided by fire walls into areas not exceeding 3,000 ft 2

, openings guarded by Type

A fire doors. In buildings for films, area on one floor shall not exceed 7,500 ft2

. Private garages, etc., not exceeding 600 ft2 may be

erected with walls of frame construction.

[55]
Class B-3

If not over one story or 20 ft, 600 ft2

, any type.

If not over one story or 30 ft, over 600 ft2

, Types

1, 2, 3, or 4. If over one story or 30 ft, Type 1. Class B-3 buildings shall be divided into areas not exceeding those for Class A buildings. Class C buildings shall be one of the following types, except schools over one story shall be Type 1. The

area may be increased 50 percent when sprinklered.

If not over one story or 20 ft, 5,000 ft2

, any type.

If not over one story or 40 ft, 20,000 ft2

, roof and

balcony may be Types 1, 2, or 3; first floor shall be Type 1, exterior of masonry.

If not over two stories or 40 ft, 5,000 ft2

, Types 1, 2, or 4. If not over two stories or 40 ft, 10,000 ft2

, Types 1 or 2. If over two stories or 40 ft, 10,000 ft2

, Type 1. Class D buildings

Seating capacity not over 600, Type 1 or 2. Seating capacity over 600, Type 1. Class E buildings shall be constructed of one of the

following types:

Class E-l

If not over two stories or 35 ft, 5,000 ft2

, Types 1, 2, 4, or 5. If not over three stories or 45 ft, Types 1, 2, or 4. If over three stories or 45 ft, Type 1. Class E-2

If not over two stories or 35 ft, Types 1, 2, or 4. If over two stories or 35 ft, Type 1. Sanitariums not over one story or 15 ft, no basement,

1,500 ft2

, may be Type 5. Class E-3. No height limitations, Type 1 required. Class E buildings other than Type 1 shall be divided

into fire areas not to exceed 5,000 ft2. Class F buildings shall be built of one of the following

types of construction:

If not over two stories or 35 ft, Types 1, 2, 4, or 5, except that single- or two-family dwellings only may

be built of frame construction of not over two and

one-half stories high.

If not over three stories or 45 ft, Types 1, 2, or 4. Class F buildings other than Type 1 construction shall be divided into fire areas of 5,000 ft2

. Miscellaneous Structures Grandstands of wood, 5,000 ft2

. The highest level

of seats shall not be more than 20 ft above ground

level and no part of canopy shall exceed 30 ft above

ground level.

4. Atlanta

(a) Heights of Buildings

No building or structure hereafter erected, except

church spires, water towers, smoke stacks or chimneys,

shall exceed the limits given in table 52 with the

following qualifications

Table 52.

Height limitations of buildings, code Atlanta

Type of buildings

Frame buildings other than dwellings or apartments. _ Frame dwellings and apartments not more than two

families _ Buildings having bearing walls of hollow terra cotta or concrete blocks

Non-fire-resistive buildings, ordinary construction

Non-fire-resistive buildings, mill construction or metal

joist construction: Without sprinklers With sprinklers _ Fire-resistive buildings.. -

Height

Feet Stories 30 2

30 2H

40 3 55 4

65 5

75 6 150 14

Group I, Public Buildings, Class B.—Buildings of

this class over three stories or 40 ft high, shall be of

fire-resistive construction, except that church spires

need not be fire resistive unless they exceed 75 ft in height.

Group III, Business Buildings, Class F.—Outside of

fire limits for isolated buildings or plants of a character not usual to city industries, such as cotton mills, the height in feet may be increased 50 percent over that permitted in table 52, but not to exceed 125 ft, and

the area may be increased 60 percent over that per- mitted under Allowable Floor Areas, table 54(c), "with

sprinklers."

(b) Allowable Floor Areas

In every building of the character named in this section the maximum area of any floor between fire walls or exterior walls, either without or with a full equipment of automatic sprinklers shall be as given in tables 53 and 54, unless otherwise qualified. Unless all floor openings are protected, areas in buildings equipped with automatic sprinklers shall not

exceed 50 percent greater than that allowed for similar buildings not so equipped but occupying similar location as to streets.

Table 53.

Allowable areas for buildings of non-fireresistive construction, Atlanta code

Front ing on

Without

sprinklers With sprinklers (increase 100 percent)

(a) Apartment houses, 3,000 ft!

(b) All other ordinary non-fire-resistive buildings, heights not exceeding

55 ft

One street... --

ft 2

5, 000

6,000

. 7,500

ft1 10,000

12, 000

15, 000 Two streets. Three or more streets -

(c) Mill-construction buildings, height limit 65 and 75 ft

One street -- 6,500

8, 000

10, 000

13, 000 16,000

20, 000 Two streets.. .. Three or more streets

[56]
Table 54.

Allowable areas for buildings of fire-resistive construction, Atlanta code

Fronting on

Without

sprinklers

With sprinklers (increase

100 percent)

(All buildings of class A, B, C, and D_

(aKLight and power stations

(.Office buildings |no restrictions as to area

(b) All other buildings not exceeding 65 ft in height

One street .

ft'10, 000

12, 000

15, 000

ft' 20, 000

24, 000

30, 000 Two streets. Three or more streets

(c) Stores, warehouses, factories, and workshops

One street 7,500

10, 000

12, 500

15, 000

20, 000

25, 000 Two streets Three or more streets

(d) The first floor only of any fire-resistive building occupied as a store may have an area of 20,000 ft 2

, and if fully protected by approved auto- matic sprinklers may be increased 100 percent or have a maximum area

of 40,000 ft'.

(c) Frame Buildings Outside of Fire Limits

1 . No frame building shall exceed two stories or 35 ft. in height, except that dwellings may have two-and onehalf stories, provided they do not exceed 35 ft. in height

or 3,000 ft2 in area.

2. No frame building, erected for any occupancy

other than buildings of Class F, shall cover a ground

area exceeding 5,000 ft2

, except as modified in para- graph 4 below; except also that a frame building

equipped with an approved system of automatic

sprinklers may have an increase in area of 66% percent,

or a total of 8,333 ft2

.

3. Frame buildings of Class F, and frame buildings

of other classes having an area exceeding 5,000 ft2 with- out sprinklers, shall not be placed within 35 ft of any

side or rear lot line; 7,500 ft2

, 100 ft. 4. The combined area of frame buildings, sheds, and

outhouses located on any lot shall not exceed 80 percent

of the lot area.

5. Outside of fire limits for isolated buildings or plants of a character not usual to city industries, such

as cotton mills, the area may be increased 60 percent over that permitted in non-fire-resistive construction given in table 53 (c), "with sprinklers."

5. Denvek

(a) Restrictions Based on Types of Construction Type I. The height of Type I buildings shall not be

limited. Type II. Buildings shall not exceed a height of 65 ft. Floor areas are limited by occupancy require- ments. Type III. Buildings shall not exceed a height of 45 ft in which height there shall be not more than

three stories. Floor areas are limited by

occupancy requirements.

Type IV. Buildings shall not exceed a height of one

story and a mezzanine floor, except that

buildings of Group I occupancy may be two

stories in height. Floor areas are limited by

occupancy requirements.

Type V. Buildings shall not exceed a height of 25 ft, in which height there shall be not more than two stories.

(b) Restrictions Based on Occupancy

Group A.—Type I construction required, otherwise no

restrictions. Group B.—Heights and areas to be limited according to table 55.

Table 55.

Height and area limitations for Group B

buildings, Denver code

Type of con- struction

Maximum

height for corresponding

areas

Maximum floor areas

Building front onIncrease

for complete sprin- kling One

street Twostreets Threestreets

I

ft C)

f 65

\ 65

/ 45

\ 35

(»)

Stories

(?) 5

13

1

1

ft

2 ft- f& Percent

II. _

Ill IV

6, 500

12, 500

5, 000

7, 500

16, 000

9, 500

16, 000

6, 500 9,500

19, 000

12,000

20, 000 9,500

12, 500

22, 000

}

100

}

100

100

" No restrictions.

Group C.—Type I construction required with certain exceptions, otherwise no restrictions. Group D.—Type I construction required, otherwise no

restrictions. Group E.—Heights and areas to be limited according

to table 56.

Table 56.Height and area limitations for Group E

buildings, Denver code

Type of construction

Maximum

height for corresponding

areas

Maximum floor areas

Building front on

Increase

for complete sprin- kling One

street Twostreets Three

streets

I

ft

f 65

\ 65

f 45

\ 35

45

Stories

(?) 5

13

1

1

ft2 ft' ft2 Percent

II

III rv_. _

5,000

9, 500

5, 000

7,500

9,500

6,500

12. 500 6,500

9, 500

12, 500

9,500

16,000

9,500

12, 500

16,000

\ 100

}

100

100

» No restrictions.

Group F.—Same as Group B. Group G.—Types I, II, III, same as Group B. Type

IV, no restrictions. Group H.—Same as Group B except Type IV is limited

to 45 ft height.

Group I.—No restrictions except as limited in height

by type of construction.

[57]
Group J.—The floor area of Types I and II construction

shall not be limited, the floor area of Types III and

IV shall be limited to 10,000 ft2 and buildings of Type V construction shall not exceed 1,000 ft. 2 The latter shall not apply to amusement-park

structures of the open skeleton-framed type or to stadiums or reviewing stands for temporary use only.

6. Seattle

(a) Maximum Building Heights

No building shall exceed a height of two and a half times the width of the widest street on which the build- ing abuts, except that towers for occupany may be

erected above said height if they are at least 25 ft from

any lot line other than a street line; if they do not

exceed an area of 25 percent of the lot area; and if they do not exceed 50 ft in length and breadth. Work shops and factories other than feed and flour

mills, shall not exceed a height of 85 ft. Stores, warehouses, and storage garages shall not exceed a height

of 100 ft. Height of Fireproof Buildings.—No fireproof building

shall exceed a height of two and a half times the width

of the widest street on which the building abuts, except

that towers for occupany may be erected above said height if they are at least 25 ft from any lot line other than a street line, if they do not exceed an area of 25

percent of the lot area, and if they do not exceed 60 ft in length or breadth.

Fireproof workshops and factories, including feed

mills and flour mills, shall not exceed 200 ft in height.

Fireproof stores, warehouses, and storage garages shall not exceed a height of 125 ft. Steel-Joist Construction.—Steel-joist construction may

be used wherever mill, ordinary masonry, or frame construction is permitted by this code. In addition, a building of this class may be built to a

greater height than permitted for a mill building, pro- vided that the occupany is that of an office building

fireproof through the third floor; place of habitation or place of refuge fireproof through the second floor. Steel-joist construction in which the joists have a web thickness of 0.2 in. or less shall not be used in the

construction of any story of a building below the top

10 stories nor in any building which exceeds 15 stories

in height.

Steel-joist construction in which the minimum thick- ness of web is greater than 0.2 in. may be used at greater heights, but shall not be used in the construction

of any story of a building below the top 15, nor in any

building which exceeds 20 stories in height.

Height of Mill Buildings.—No mill-construction building shall exceed a height of six stories or 75 ft, nor

shall it be higher than 85 ft at any point.

Height of Ordinary Masonry Buildings.—No ordinary

masonry building shall exceed a height of four stories or 50 ft, nor shall it be higher than 60 ft at any point.

Height of Frame Buildings.—No frame building shall exceed a height of three stories or 35 ft, nor shall it be

higher than 45 ft at any point.

(b) Maximum Building Areas

In any building, a floor occupied as a place of habitation, refuge, or detention shall, except as hereinafter provided, be divided by fire walls, so located that the

area of the floor shall not exceed the number of square

feet indicated below:

Mill buildings 12, 000

Ordinary masonry buildings 8, 000 Frame buildings 6, 000

In any building, a floor occupied by . one or more

stores, offices, factories, workshops, garages, warehouses, stables, hangars, or for purposes producing

equivalent fire hazard, shall except as hereinafter provided, be divided by fire walls so located that the area

of no floor shall exceed the number of square feet indi- cated in table 57, except that fireproof office buildings

are not limited as to the area of any floor used exclusively

for office purposes. Table 57.

Permissible areas of commercial buildings,

Seattle code

Location Fireproof

buildings Millbuildings

Ordinary masonry

buildings Frame

buildings

fp fp ft' ft' On lots with more than one

street frontage 20,000 15, 000 10,000 8,000 On lots with only one street frontage... 18,000 14,000 9,000 7,200

Buildings Housing Incombustible Materials.—In the Fourth Building District, one-story factory buildings

manufacturing exclusively products which are mainly

composed of incombustible materials, and one-story

warehouses used entirely for the storage of incombustible materials, are not restricted as to the undivided

floor area of the first story if the building is constructed

of fireproof, mill, or ordinary masonry construction, or frame construction having floor, roof, and wall sheathing of 2- by 6-in. tongue-and-groove lumber, etc., or when the building is constructed of equally fire-resistive material.

If located in the Fourth Building District, two-story

fireproof, mill, ordinary masonry, or frame buildings,

providing the latter are constructed as specified in this section for one-story frame buildings, may, if used exclusively for the manufacturing therein of products

which are composed mainly of incombustible materials,

have undivided first- and second-floor areas one-third

greater than indicated in the above table. In the Second and Third Building Districts, either one-story fireproof warehouse buildings or one-story

warehouse buildings built entirely of incombustible

materials may be constructed and may have unlimited

undivided areas, provided such warehouses are used

for the storage and handling of nothing but incombustible materials, and are not nearer than 15 ft to any

frame building, except where separated by masonry

division walls. Provided further, that any building having floor

[58]
areas increased as permitted above shall be equipped

in each story with one or more 2-in. standpipes, etc. Allowable Floor Areas with Sprinklers.—A store build- ing of fireproof construction having all floor openings not specifically exempted enclosed with fireproof construction and fire doors, is not restricted as to its undivided floor area, provided such building is equipped

throughout with an automatic sprinkler system constructed as specified.

The allowable floor area of any building having its stairways, elevator shafts, and other floor openings enclosed as required by this code, and having its means

of egress complying in all respects with this code, may

be increased 100 percent if the building is equipped

throughout with an automatic sprinker system.

Attic Division.—In nonfireproof buildings, all attics or unfinished spaces between the ceilings and roofs must be divided into compartments having areas not

to exceed 3,600 ft2

. In fireproof buildings the attic space shall not be used where temporary wood roofs are permitted.

Such attic shall be divided into areas not to exceed

1,800 ft2

. Incombustible Service Stations and Auto Parking Lot

Shelters.—Incombustible service stations may comprise more than one building. All such buildings . . . shall be included in computing the allowable area . . . An incombustible service station shall not be larger

than 3,000 ft2 in area. Incombustible shelters on auto parking lots shall have no greater area than 50 ft. 3

V. PERMISSIBLE MATERIALS

1. New York

Class I. Fireproof Structures

Walls.—Masonry or reinforced concrete or masonry in combination with fireproofed iron or steel. Structural Members.—Steel, iron, or reinforced concrete. Floors.—Reinforced concrete, brick, or hollow-tile arches, reinforced poured gypsum or precast units. Roofs.—Same as floors except protection may be omitted

from roof trusses: (1) in one-story structures, (2) in multistory structures if supporting roof loads only

and there is a clear height of 20 ft below lower chord

of trusses, (3) if a continuous ceiling having a fire- resistance rating of 3 hr is provided below lower chord of truss and space above ceiling is completely

enclosed and firestopped, and contains no passage- ways or apparatus of any kind. Trim and Finish Floors.—May be of wood in buildings 150 ft or less in height. No height limitation if wood is treated to make it fire resistive. Doors, Frame, and Sash.—May be of wood in buildings 150 ft or less in height, with no height limitation if wood is treated to make it fire resistive, except that

exterior window frames and sash to be of incombustible materials throughout full height in buildings over 150 ft in height.

Subdividing Partitions.—To be of incombustible materials or wood treated to render it fire resistive, ex- cept that in spaces without combustible occupancies, such as require a permit from the fire commissioner,

partitions may be of a single thickness of wood, or wood and glass may be used in structures 150 ft or

less in height to subdivide rooms or spaces 5,000 ft2 or less in area, if separated from adjoining rooms or

spaces, corridors, elevators, and stair enclosures by

fireproof partitions or walls made of incombustible

materials. Roof Coverings.—Required to pass specified tests.

Class II.—Fire-protected Structures

Walls.—Masonry or reinforced concrete or masonry in combination with fireproofed steel or iron. Structural Members.—Steel, iron, or reinforced concrete. Floors.—Reinforced concrete slabs, brick, or hollow-tile arches, reinforced poured gypsum or precast units. Roofs.—Same as for Class I, Fireproof Structures. Trim and Finish Floors.—Interior doors and sash with

their frames, trim and casings and finish floors may

be of wood.

Roof Coverings.—Required to pass specified test.

Class III. Nonfireproof Structures

Exterior and Fire Walls.—Masonry or reinforced

concrete. Structural Framework.—Wood or unprotected steel or

iron. Floors. —May be of wood except in residence structures more than three stories and basement in height and in other structures four stories or more in height, the

floor above cellar or basement and columns below

such floors are to be of masonry, reinforced concrete or fireproofed steel or iron. Roofs.—Wood sheathing.

Trim, Doors and Finish Floors.—May be of wood.

Stair Enclosures and Shafts.—Incombustible materials. Roof Coverings.—Required to pass specified test.

Class IV. Wood Frame Structures

Footings, foundations and columns or other supports of

first-floor framing to be of incombustible materials.

Exterior and interior construction and finish may be of wood.

Roof Coverings. —Required to pass specified test.

Class V. Metal Structures

Exterior Walls.—Metal, flat or corrugated, cementasbestos composition sheets, or of incombustible material other than masonry.

Structural Framework.—Metal.

Roofs.—Same as for exterior walls. Roof Coverings.—Required to pass specified test.

[59]
Class VI. Heavy Timber Structures

Exterior Walls.—Masonry or reinforced concrete. Structural Framework.—Wood. Beam and girders not

less than 6- by 10-in. Posts or columns not less than

8 in. If steel is used, it must be protected as for Class II construction.

Floors.—Splined or T & G plank 3 in. thick covered with 1-in. flooring laid crosswise or diagonally or planks set on edge, floor 4 in. thick. Floor immediately over basement or cellar and all construction below it, including columns, same as for Class II construction.

Roof.—Planks 2}i in. thick and beams supporting roof not less than 6 in. in smallest dimension.

Shafts and Stairways.—Enclosed in materials or assemblies having a fire-resistance rating of at least 2 hr. Roof Coverings.—As required by zoning.

2. Boston

Type I. Fireproof Construction

Shall be of incombustible materials in all structural

parts. Walls.—(4 hr) Reinforced concrete, masonry, or steel frame. May be finished except on the outside of exterior walls and within enclosures of vertical openings with wooden or other combustible wainscoting, insulating, or acoustical material. Columns and Framing.—(4 hr) Structural steel or rein- forced concrete.

Floors.—(3 hr) Steel, reinforced concrete, brick or structural clay tile arches, reinforced gypsum, or combinations of these materials or other approved

systems.

Roofs.—(3 hr) Steel, reinforced concrete, brick or struc- tural clay tile arches, reinforced gypsum, or combinations of these materials or other approved systems.

Partitions.—Reinforced concrete, masonry, steel frame,

except that within one tenancy nonbearing partitions

may be of wood.

Flooring, Trim, and Decorative Wall, and Ceiling Finish.—May be wood or other combustible but not

highly inflammable material. Doors, Frames and Sash.—May be of wood except where

fire doors or fire windows are required.

Roof Coverings.—Fire retardant (Class A or B) or Ordinary (Class C). Type II. Semifireproof Construction

Shall be of incombustible materials in all structural

parts. Walls.—(4 hr) Reinforced concrete, masonry, or steel frame. May be finished, except on the outside of exterior walls and within enclosures of vertical openings with wooden or other combustible wainscoting,

insulating or acoustical material. Columns and Framing.—(2 hr) Structural steel or rein- forced concrete.

Floors.—(1 hr) Incombustible materials.

Roofs.—(1 hr) Incombustible materials.

Partitions.—Reinforced concrete, masonry, steel frame,

except that within one tenancy nonbearing partitions

may be of wood.

Flooring, Trim, and Decorative Wall and Ceiling Finish. —May be wood or other combustible but not

highly inflammable material. Doors, Frames and Sash.—May be of wood except

where fire doors or fire windows are required.

Roof Covering.—Fire-retardant (Class A or B) or Ordi- nary (Class C).

Type III. Heavy Timber and Masonry Construction

Exterior Walls.—(4 hr) Masonry or other incombustible materials. Interior face may be finished with

wood or other combustible wainscoting or acoustical material with no concealed spaces between finish and wall. Structural Frame.—Heavy timber or protected steel (1 hr) , or steel pipe columns filled with concrete.

Floors.—Heavy timber without concealed spaces, or protected steel (1 hr). Roofs.—Heavy timber without concealed spaces.

Partitions.—Solid wood, or hollow wood filled with

incombustible material. Doors, Frames and Sash.—May be of wood except where

fire doors or fire windows are required. Fire doors

shall have incombustible thresholds. Roof Coverings.—Fire-retardant (Class A or B). Type IV. Light Wood and Masonry Construction

Exterior Bearing Walls.—(4 hr) Masonry or other in- combustible materials. Other Walls.—Wood except party or fire walls. Structural Frame.—Wood or structural steel. Floors.—Wood.

Roofs.—Wood.

Partitions.—'Wood.

Flooring.— Wood, tile, concrete. Doors, Frames and Sash.— May be of wood except

where fire doors or fire windows are required. Fire doors shall have incombustible thresholds. Roof Coverings.— Fire-retardant (Class A or B). Type V. Metal Frame Construction

Walls.— Unprotected metal or other incombustible

materials. Structural Frame.— Unprotected metal or other incombustible materials.

Floors.—Unprotected metal or other incombustible

materials.

Roofs.—Unprotected metal or other incombustible

materials. Doors, Frames and Sash.—May be of wood, except

where fire doors or fire windows are required.

Roof Covering.—Fire-retardant (Class A or B) or Ordi- nary (Class C). Type VI. Wooden Frame Construction

Walls.— Wood.

Structural Frame.— Wood, structural steel, cast iron, or reinforced concrete.

[60]
Floors.—Wood.

Roofs.—Wood.

Partitions.—Wood.

Flooring.—Wood, tile, concrete. Roof Coverings.—Fire-retardant (Class A or B).

3. Minneapolis

Type I. Fireproof

Bearing Walls.—Masonry.

Nonbearing Partitions.—Brick, concrete, concrete block, structural clay tile, plaster on gypsum or metal lath on metal studs.

Vertical Members.—Masonry, concrete, reinforced concrete, or fireproofed ferric materials. Horizontal Members.—Reinforced concrete beams or

lintels, fireproofed steel beams and girders. Floors.—Any fire-resistant material properly fire- proofed, 2-hr rating required. Wood sleepers may

be embedded when protected underneath by mini- mum of 2-in. concrete or gypsum. Floor finish may

be of wood not exceeding in. thick. Roofs.—Any material permitted for floors. Formed

steel roofs protected with ceiling not less than % in. permitted in buildings not exceeding three stories in height, but in one-story buildings regardless of height.

Roof coverings, incombustible material. Wood Permitted.—Mezzanine floors to be \% in. thick. Window frames and aprons, 1st floor. Partitions around cashier's cages, wash stands, lockers, closets. Partitions separating offices within space occupied by same tenant may be wood panel construction. (Wood stud and lath prohibited.) Nailing blocks

brick size permitted. Wood trim permitted. Wood

doors permitted except to stairs, elevators or other

shaft enclosures, fire division walls, closets for gas

meters, electric closets communicating with open

shaft to other parts of building.

Type II. Slow Burning

Bearing Walls.—Mason^.

Partition Walls.—Fireproof or wood stud, with ex- panded metal lath and plaster on both sides or any

other partition which will withstand a 1-hr fire test. Wood furring and lath prohibited.

Enclosures.—Area over 9 ft2

, masonry bearing walls, or

partition walls of brick, tile, concrete or gypsum 6 in. thick. Under 9 ft2

, metal lath and plaster on metal

studs, supported on steel frame. Enclosures shall be continuous and no wood floor members shall project

into or through enclosure partitions.

Vertical Members.—Fireproof or wood posts not less than 56 in. 2 in cross-sectional area. Horizontal Members.—Concrete, steel, or wood not less than 52 in.2 in section area. Wood joists less than

70 in.2 in cross-sectional area solid. Over 70 in. 2 in cross-sectional area may be built up.

Floors.—Type I, or wood subfloor minimum 1% in. thick covered with waterproof paper and not less

than Ys-m. floor covering. If subfloor is less than 3M> in. thick, it shall be matched. Under side of floor joists shall not be sealed except when sealed with metal lath and plaster. Floors permitted with joists not less than 2 in. thick and having floor as required and pro- tected with a ceiling of metal lath and plaster of %-in. minimum thickness.

Roofs.—Similar to floors except 1%-in. matched roof, covered with incombustible roofing. One- and twostory buildings only may have %-in. roof boards. Where attic space is used, %-in. fireproof protection

required. Solid or built up wood roof trusses per- mitted if compression members exceed 52 in. 2 with

tension members similar or protected with %-in. metal

lath and plaster.

Stairs.—Fireproof or 1%-in. wood flooring, stringers

and joists protected on soffits with %-in. protection.

No wooden stairs or landings shall be in contact with

wood floors. Windows.—May have wood frames except where re- quired to be fire windows.

Bays, Oriels, Porches, Balconies Incombustible.—Cornices, eaves and gutters not extending over lot line on buildings not over three stories or 40 ft may be

wood protected with metal. All others incombustible. Roof Structures.—Towers, dormers, spires and cupolas

not over 200 ft2 and not nearer than 20 ft to lot line may be wood covered with incombustible material,

if not over 30 ft in height from supporting masonry or

roof and not over 100 ft from grade. All other structures, incombustible but steel members not fire- proofed. Such structures not of incombustible

construction sealed at bottom by fire doors or metal-covered doors. Studies and Dormers.—When less than 200 ft2 and not

over one story or 16 ft measured from roof on buildings not over three stories or 40 ft may have wood

walls metal covered, (No. 26 U. S. gage) and roof as on remainder of structure. Type III.—Skeleton and All Steel

Walls and Partitions.—Enclosing walls of masonry, or under specified conditions of metal lath and 2-in. plaster, and interior bearing walls of masonry. Interior nonbearing walls, any material permitted in Type II. Enclosures.—No enclosure required around stairs and

shafts except that where there is a basement the stair- well and other openings through first floor shall be

enclosed with 8-in. masonry and provided with a self- closing fire door of Type B.

Vertical Bearing Members.—Masonry or cast iron and

steel unprotected.

Horizontal Members.—Reinforced concrete, unprotected

steel, and wood of sizes permitted in Type II. Floors.—Where basement is provided, first floor over and walls around and stairs leading to heating-plant room, fireproof construction.

Roof.—Concrete, or steel trusses, or beams with wood

purlins with 1%-in. thick sheathing for buildings up

[61]
to 45 ft in height. Concrete, unprotected steel, with

reinforced concrete or gypsum roofs for buildings up

to 75 ft in height.

Roofing.—Incombustible.

Windows.—Wood frames except where required to be

fire windows.

Trim—Wood.

Type IV. Ordinary Construction

Enclosing Walls.—Masonry.

Partitions.—Wood studs with wood lath or %-in. gypsum lath plastered or %-in. gypsum wallboard

permitted except for fire or division walls, stair, elevator, or shaft enclosures, which shall be brick, structural clay tile, gypsum, or concrete blocks.

Vertical and Horizontal Members.—Below first-floor line: metal, masonry or wood. All other vertical and horizontal members, any material not more

combustible than wood.

Floors and Roofs.—Any material not more combustible

than wood.

Roof Covering.—Incombustible material. Bays and Oriels.—Wood covered with No. 26 U. S. gage metal or other material of equal fire rating.

Up to two stories. Porches and Balconies.—When 3 ft from property line and not above third story, wood porches. Above

third story, incombustible. Type V. Buildings of Wood Construction

Foundations.—Masonry.

Structural Members.—Below first floor, girders shall be

masonry or metal. Wooden columns may be used

in buildings with basements if foundations or footings

under posts extend 2 in. above basement floor. Wood and other combustible materials may be used

throughout, if fire-stopped at each floor, and the

other materials meet same fire rating as pine.

4. Atlanta

I. Frame Construction

May be of wood throughout, except as follows: Residence Row Houses.—Dividing walls of incombustible

materials, or wood studs with spaces filled solidly

with incombustible materials and having metal

lath and plaster or plasterboard, and, where there

are more than 3 houses, alternate division wall of masonry to above roof. Stairways and Shaft Enclosures.—Wood covered with

plaster on metal lath or fiber plasterboard, or with

plasterboard covered with metal. Roof Coverings.—Standard asphalt rag-felt prepared

roofings and shingles or equivalent approved and

labeled by Underwriters' Laboratories.

II. Non-Fire-Resistive Construction

Exterior and Party Walls: Ordinary and mill. —Incombustible, except as

follows: Wood lintels for openings less than 4

ft, wood nailing blocks, and wood furring

fire-stopped with masonry.

Floor and Roof Framing Members:

Ordinary and mill. —Wood or steel; 6-in. minimum

wood or steel protected as for Type III in Mill Construction. Columns or Interior Supporting Walls or Partitions: Ordinary and mill.—Masonry, protected steel, or

8-in. minimum wood, except in dwellings and

other ordinary construction not more than one

story in height, wood-stud partitions may be

used; steel protected as for Type III in Mill construction. Walls and Ceilings:

Ordinary.—No limitations except that wood wainscot must have plaster behind it. Mill. —Wood exposed or protected steel with no

concealed spaces.

Partitions: Ordinary.—No limitations. Mill.—Incombustible, unless less than four stories, or if sprinklered may be 2-in. solid wood.

Floor and Roof Sheathing:

Ordinary.—No limitations. Mill.—Floors, 3 in. wood, splined or T & G and

covered with 1-in. flooring diagonal or crossways.

Roofs, 2Y2 in. wood, splined or T & G. Stairways or Shaft Enclosures: Ordinary.—Except for dwellings same as for Type

III, except if not over two stories, walls may be

masonry partitions; woodwork other than guides

and elevator cars, exposed on inside of shaft, to be covered with metal lath and plaster. Mill.—Masonry walls except in buildings not over

three stories sprinklered or two stories not

sprinklered, wood or metal studs with spaces

filled with incombustible material and plastered on metal lath; openings to have approved fire doors. Roof Coverings.—For dwellings and buildings not over two stories or 30 ft high, and 2,500 ft2 area, not used

for factories, warehouses, or mercantile purposes, may

be standard asphalt rag-felt prepared roofing and

shingles. All other buildings shall have roof covering of standard quality, such as brick or concrete surface,

clay or cement tile, tin or slate, asbestos shingles

%-in. minimum thickness, four-ply built-up pitch and

felt with gravel or slag surface, four-ply asbestos- asphalt built up smooth or grit surface, or equivalent

approved and labeled by Underwriters Laboratories.

III. Fire-Resistive Construction

Exterior and Party Walls.—Masonry or incombustible.

Floor and Roof Framing.—Masonry or protected struc- tural steel. Partitions.—Incombustible, masonry or protected steel. Wall and Ceiling Surfaces.—Incombustible except wood

wainscot not more than 3 ft high. Floor Surfaces.—Wood or other.

[62]
Floor sleepers, grounds, bucks, nailing blocks entirely

embedded in incombustible materials, may be wood.

Interior windows, doors, with frames, trim and casings,

and interior finish.—When backed up solidly with

fire-resistive materials, except as otherwise limited,

may be of wood.

Stairway and shaft Enclosures.—Masonry walls or parti- tions with floor surfaces and trim of approved in- combustible material. Roof Coverings.—Same as for Type II.

5. Denver

Type I. Fire- Resistive Construction

Foundations.—Solid masonry or reinforced concrete.

Exterior, Fire, and Court Walls.—Masonry or reinforced

concrete.

Structural Framework.—Steel, iron, or reinforced concrete. Floors.—Reinforced concrete, brick or hollow-tile arches or reinforced gypsum.

Roofs.—Same as floor except that roof members in buildings not over 65 ft high, having 2-hr fire-resistive ceiling beneath, may be of wood.

Partitions.—Incombustible materials except that within one tenancy they may be wood or wood and glass. Trim and Finish Floors.—May be of wood.

Doors, Frames, and Sash.—May be of wood, except for openings required to be protected.

Insidation.—If in board form and backed with Malls and ceilings of 1-hr fire-resistive construction, may

be combustible, except in attic and concealed spaces. Roof Coverings.—Fire retardant.

Type II. Heavy Timber Construction

Foundations.—Solid masonry or reinforced concrete.

Exterior, Fire, and Court Walls.—Masonry or reinforced

concrete. Shaft Enclosures.-—Masonry or reinforced concrete ex- cept they may be of wood in buildings not over three

stories and completely sprinklered.

Structural Framework.—Reinforced concrete, steel, or

solid wood.

Floors.—Same as Type I or solid wood.

Roofs.—Same as floors. Partitions.—One-hour fire-resistive or solid wood.

Trim, Finish Floors'—May be of wood.

Doors, Frames, and Sash.—May be of wood except in openings required to be protected.

Insulation.-—If in board form and backed with walls and

ceilings of 1-hr fire-resistive construction or applied

without air space to under side of floors and roof sheathing may be combustible except in attic and

concealed spaces. Roof Coverings.—Fire retardant.

Type III. Ordinary Masonry Construction

Foundations.—Solid masonry or reinforced concrete.

Exterior, Fire, and Court Walls.—Masonry or reinforced concrete except that (rabies of Group I (dwellings)

and Group J (garages, etc.) may be of wood or unprotected metal frame above the plate line. Structural Framework.—Steel, iron, reinforced concrete, masonry, or wood.

Floors.—Reinforced concrete, masonry, steel, iron, or wood.

Roofs.—Same as floors. Partitions and Shaft Enclosure.—May be of wood.

Trim, Finish Floors.—May be of wood.

Doors, Frames, and Sash.—May be of wood except in openings required to be protected.

Insulation.—Combustible insulating materials must be

treated to render them slow-burning if placed in concealed spaces. Roof Coverings.-—Fire retardant except in fire zones 3 and 4 where wood shingles and the lighter combustible

roofings can be used. Type IV. Metal Frame Construction

Foundations. —Masonry or reinforced concrete.

Exterior Walls.—Metal or other incombustible materials.

Partitions.—Metal or other incombustible materials. Structural Framework.—Steel, iron, masonry or rein- forced concrete.

Floors.—Incombustible materials or wood planks or

blocks laid directly on the earth. In Group I (dwellings) and Group J (garages, etc.), floors may

be of wood on metal joists. Roofs.—Metal or other incombustible materials except

that 4-in. or larger wood purlins may be used. For Types I and J occupancies wood sheathing may be

used on metal rafters. Doors, Frames, and Sash.—May be of wood except in openings required to be protected. No opening

protection required for Groups I and J occupancies.

Insulation and Linings. —Incombustible except that combustible insulating materials in board form may

be used in buildings of Groups I and J occupancies.

Roof Coverings.-—To be metal or "Fire Retardant"

except that for Groups I and J occupancies "Ordinal" roof coverings including wood shingles may be used in fire zones 3 and 4.

Type V. AVood Frame Construction

Foundations.—Masonry, reinforced concrete, or post

and girder. Footings, masonry or concrete.

Exterior and Interior Construction and Finish.—May be

of wood.

Insulation.—If in loose form and placed in joist or stud

spaces, combustible insulation must be treated to render it slow-burning.

Roof Coverings.—All accepted coverings, except "Fire Retardant" coverings are required in fire zones 1 and 2. 6. Seattle

Fireproof Buildings and Steel Joist Buildings

Except as otherwise provided, these buildings must

be constructed entirely of fireproof or incombustible

material.

[63]
Walls.—Masonry or masonry in combination with

fireproofed iron or steel. Structural Framework.—Masonry, reinforced concrete,

or fireproofed steel, for columns, beams, and girders.

Where permitted, steel joists having webs more than

0.2 in. thick may be used in buildings not over 20

stories high for the top 15 stories; steel joists having

webs 0.2 in. thick or less may be used in buildings not over 15 stories high for the top 10 stories; protected by 1 in. of plaster on metal furring in either

case. Floors.—Concrete or masonry arches. Roofs.—Same as floors except buildings designed for additional stories may have temporary flat roofs of wood supported on top slab. Trim.—Wood, when backed without intervening space by incombustible material, except for wainscot in public halls. Finish Floors.—Wood except in public corridors and

enclosures. Doors, Frames, and Sash.—Wood except where fire- proof openings are specifically required.

Roof Coverings.—Coverings corresponding to classes 1 and 2 of this report.

Mill Buildings

Exterior and Court Walls, Piers, and Columns.—Masonry

or masonry in combination with fireproofed iron or

steel. Interior Columns.—Wood, not smaller than 10 in.; iron or steel, fireproofed, if carrying masonry walls or

floors. Interior Beams, Girders, Joists, and Stair Stringers.—

Structural steel, wood, or fireproof construction. Minimum dimensions of wood, 8 in. for girders and

beams, 6 in. for joists, 4 in. for stair stringers. Steel beams in cellars and basements fireproofed or pro- tected with 1-in. plaster on metal lath. Floors.—Solid wood lower layer and board upper layer.

Any space between layers must be filled with incombustile material or firestopped into areas not exceeding 32 ft2

. Roofs.—Same as under layer of floor. May be 2-in. tongue-and-groove plank on 4-in. minimum timbers

if protected by a suspended plaster ceiling. Ceilings.—Metal lath and plaster on steel supports if ceiling space is firestopped into areas not exceeding

1,800 ft2

. Same on wood supports if space is fire- stopped into areas not exceeding 32 ft2

. Partitions.—Fireproof; incombustile; or (a) double

plank; (b) single plank plastered both sides; (c) lami- nated of 2- by 4-in. wood and covered both sides with

plaster, 1-in. wood sheathing, plasterboard, %-in. asbestos, or galvanized metal with joints locked or lapped iy2 in., (d) 2% in. plaster on flat wood studs and lath. Stairway Enclosures.—In warehouses, factories, and

workshops over three stories high, fireproof; three

stories or less, two thicknesses of vertically placed

matched 1%-in. lumber with 30-lb asbestos paper

between and joints broken. If stairway leads to place of assembly, habitation, refuge, or detention

through first story used for a different purpose, over

three stories high, fireproof up to top of second-floor

level; three stories or less, two thicknesses of vertically placed 1%-in. lumber with 30-lb asbestos paper between and joints broken or a mill building

partition. In buildings containing places of assembly or where basements are used for storage or sale of combustible goods or contain a boiler in operation

or equivalent hazard, fireproof up to top of ground

floor. In buildings over three stories, required enclosure includes halls connecting successive runs of

stairs. Elevator Shaft Enclosures.—In all basements, within 20 ft of stairway, or in buildings used as places of habitation, refuge, or detention; fireproof. Passenger elevator shafts elsewhere, fireproof. If not more

than four stories and basement high, solid stud or approved laminated plank construction 3% in. thick,

in either case lined with tin as for fire doors or plas- tered both sides. Freight elevator shafts elsewhere

6-ft high solid or open wood or metal wainscot at all floors; in stores, factories, and workshops housing more than 25 employees per freight elevator per floor or more than 100 employees per freight elevator, fire- proof or approved laminated plank as for passenger

elevators. Other Shaft Enclosures.—Mill building partitions the

solid wood portion of which shall be not less than

4 in. thick, protected on the inside by lath and plaster,

two thicknesses of plasterboard or plasterboard cov- ered by sheet metal either lock jointed or lapped at

least X% in. Roof Coverings.—Coverings corresponding to classes 1 and 2 of this report.

Ordinary Masonry Buildings

Exterior and Court Walls and Piers.—Masonry or masonry in combination with iron or steel, fireproofed

except in first story of one-story buildings.

Interior Framework.—May be wood.

Flooi s. —At least two thicknesses of wood.

Roof Sheathing.—Tight single thickness of wood.

Partitions and Ceilings.—Plastered if of wood. Metal

lath or plasterboard required on. all ceilings of base- ments and cellars except apartments and sleeping rooms, and on the sides and ceilings of public corridors, stair halls, and soffits of public stairs. Stairway Enclosures.—Same as for mill buildings. Elevator Shaft Enclosures.—Same as for mill buildings. Other Shaft Enclosures.—In buildings over three stories high, same as for mill buildings. In buildings of three stories or less, mill building partitions or single

2- by 6-in. lumber, tongue-and-groove, protected on

the inside by lath and plaster, two thicknesses of plasterboard, or plasterboard covered with sheet metal either lock-jointed or lapped at least l}4 in. Roof Coverings.—Coverings corresponding to classes 1 and 2 of this report.

[64]
Frame Buildings

May be of wood throughout except as noted.

Plaster.—Required on all frame walls, partitions, and

ceilings in places of assembly, detention, or habitation other than a detached one-family residence. Not required in basement of two-family apartment

except on ceilings of furnace and habitable rooms. Detached one-family residences over one story high,

must have plaster or plasterboard in habitable rooms, bath rooms, halls, and corridors. Shaft Enclosures.—Same as for ordinary masonry

buildings.

VI. REQUIRED DEGREE OF FIRE RESISTANCE OF STRUCTURAL MEMBERS

1. New York

Class 1. Fireproof StructuresFire-resistance ratings

ftr Exterior walls, fire walls, party walls, piers, columns, and interior structural members

which carry walls 4 Other girders, fire partitions, floors including

beams and girders, beams, roofs, and floor

fillings, required stairway enclosures 3 Required stairway enclosures in schools 2 Permanent interior partitions 1

Class 2. Fire-Protected Structures

Exterior walls, shafts; required stairway enclosures in structures more than 50 ft in height 3 Required stairway enclosures in structures 50

ft or less in height 2 Protection of structural members in exterior

walls, those which support walls, shafts, and interior columns in public and commercial buildings 3 Protection of interior columns in residence

structures 2 Floor above cellar or basement 3 Other floors and roof V/i Other walls and partititions 1

Class 3. Nonfireproof Structures

Exterior walls 3 Floor above cellar or basement and columns

below such floors (except in residence buildings three stories and basement or less in height and other structures not over four

stories or 40 ft in height) 3

Shafts and required stairway enclosures ex- cept as below 2 Shafts and required stairway enclosures in residence buildings, three stories and base- ment or less in height and in other structures not over four stories or 40 ft in height 1

VI. REQUIRED DEGREE OF FREE RESISTANCE OF STRUCTURAL MEMBERS—Con.

1. New York—Continued

Class 6. Heavy Timber Construction

Fire-resistance ratings

hr Exterior walls 3

Shafts and required stairway enclosures 2

2. Boston

Type I. Fireproof

Exterior bearing walls and frames 4

Floors and roofs 3

Type II. Semifireproof Exterior bearing walls 4

Columns and frames 2

Floors and roofs 1 Type III. Heavy Timber and Masonry

Exterior bearing walls 4

Type IV. Light Wood and Masonry

Exterior bearing walls 4

3. Minneapolis

Requirements are not expressed in degree of

fire resistance.

4. Atlanta

Requirements are not expressed in degree of

fire resistance.

5. Denver

Type I. Fire-Resistive Construction

Exterior bearing walls, firewalls, and fire- division walls 4

Other exterior walls and inner court walls 3

Partitions (except that partitions within 1 tenancy can be %-in. wood or wood and

glass) 1 Enclosure of vertical openings 2

Structural members (buildings more than 8

stories, 85 ft) 4

(buildings 8 stories, 85

ft or less) 3

Floors (buildings more than 8 stories, 85 ft) . _ 3

(buildings 8 stories, 85 ft or less) 2

Roofs, same as floors except (a) that the framing may be unprotected if there is a 3-hr

ceiling separating it from the top story, and

(b) that the roof construction may be of

non-fire-resistive construction if the building

is not over 65 ft in height and there is a 2-hr

self-supporting ceiling separating it from the

top story.

[65]
VI. REQUIRED DEGREE OF FIRE RESISTANCE OF STRUCTURAL MEMBERS—Con.

5. Denver

Type II. Heavy Timber Construction

Fire-resistance ratings

hr Exterior and inner court walls and fire walls- _ 4

Partitions 1 Partitions may be of 2 layers of 1-in. matched boards. Enclosure of vertical openings 2 For completely sprinklered buildings not over 3 stories in height the enclosures may be of wood.

Structural members

Columns, steel or reinforced concrete 3 Columns, 8 in. wood minimum are per- mitted. Beams and girders, steel or reinforced concrete 2 Beams, 6 in. wood minimum are per- mitted.

Floors, steel or concrete 2 4 in. solid wood floors are permitted.

Roofs, 2Y2 in. solid roof sheathing is per- mitted.

Type III. Ordinary Masonry Construction

Exterior and inner court walls and fire walls.. 4

Partitions (bearing) except Groups I and J occupancy 1 Enclosure of vertical openings 1

Type IV. Metal Frame Construction

No requirements except fire walls 4

Type V. Wood Frame Construction

No requirements except fire walls 4

6. Seattle

Requirements are not expressed in degree

of fire resistance.

VII. PERMISSIBLE OCCUPANCIES

1. New York

Class 1. Fireproof Structures.—All occupancies.

Class 2. Fire-Protected Structures.—All except certain public occupancies.

Class 3. Nonfireproof Structures.—All except special

occupancies.

Class 4- Wood Frame Structures.—Residence, public,

and certain business occupancies.

Class 5. Metal Structures.—Commercial occupancies.

Class 6. Heavy Timber Structures.—All except certain public occupancies.

2. Boston

Type I. Fireproof.—All occupancies.

Type II. Semifireproof

.

—All occupancies except theaters and detention buildings.

Type III. Heavy Timber and Masonry.—All occu- pancies except theaters and detention buildings, and

in first and second zones, schools. Type IV. Light Wood and Masonry.—All occupancies

except theaters, schools in the first and second

zones, detention buildings, and public garages and

dry-cleaning establishments more than two stories or 600 ft 2

. Type V. Metal Frame.—All occupancies except theaters, schools in the first and second zones, detention

buildings, and large dwellings.

Type VI. Wooden Frame.—All occupancies except

theaters, schools in the first and second zones, de- tention buildings, public garages, dry-cleaning

establishments, and certain garages for six cars or less.

3. Minneapolis

Type I. Fireproof.-—All occupancies.

Type II. Slow Burning.—All occupancies except theaters seating more than 600, Class B-2 and E—3. Type III. Skeleton and All-Steel—Class A, B-l, B-3,

and C, permitted; other occupancies prohibited.

Type IV. Ordinary.—All occupancies except Clsas B-2,

E—3 and theaters. Type V. Frame.—Class A, B-l, B-3, C, E-l, and F

occupancies permitted.

4. Atlanta

Frame Construction.—Class B, C, D, and E occupancies

permitted.

Non-Fire-Resistive Construction: Ordinary Construction.—Certain schools of Class A

occupancy, and Class B, C, D, and E occupancies

permitted. Mill Construction. —Certain Schools of Class A

occupancy, Class B, C, D, and E, and Class F except

garages, oil houses, oil refineries, rendering plants,

smoke houses, varnish works, etc., permitted.

Fire-Resistive Construction.—All occupancies permitted.

5. Denver

Type I. Fire-Resistive Construction.—All occupancies.

Type II. Heavy Timber Construction.—All occupancies

except Groups A, C, and D permitted. However,

one-story schools with not over four classrooms and

private schools having not more than 25 students

are permitted under this construction. Type III. Ordinary Masonry Construction.—All occupancies except Groups A, C, and D permitted. Same

exceptions as for Type II. Type IV. Metal Frame Construction.—All occupancies

except Groups A, C, and D permitted. Same

exceptions as for Type II. Type V. Wood Frame Construction.—Groups I and J

occupancies permitted.

[66]
6. Seattle

Fireproof Construction.-—All occupancies.

Steel Joist Construction.—All occupancies. Mill Construction.—Churches, capacity up to 1,750: assembly halls, capacity up to 1,500; assembly halls used exclusively for dancing, seating capacity up to

3,000; theaters outside First and Second Building

Districts, capacity less than 750; theaters outside

First Building District, one story, capacity not over

1,000; schools, three stories and basement, capacity

1,000; places of refuge and detention, three stories. Ordinary Masonry.—Churches, capacity 750; theaters outside First and Second Building Districts, capacity

less than 750; schools, capacity 300 or less, not over two stories; garages, not more than 550 ft 2

. Frame Construction.—Churches, capacity 750; schools not over two stories and basement, capacity 300:

garages, 550 ft 2

.

VIII. DISCUSSION OF CURRENT BUILDING

CODE RESTRICTIONS IN THEIR RELATION

TO TYPES OF CONSTRUCTION

1. Classification of Buildings by Type of Construction

A review of the classifications in the six codes cited above indicates that the types defined could be placed

in four groups, as recommended in the present report, as far as the application of restrictions related to fire safety is concerned. Thus, if the Fireproof type is taken to comprise a range in fire resistance of structural members, it can include also the Fire-protected type

(New York), and Semifireproof type (Boston). The

Incombustible type defined in this report would include Metal, Metal Frame, and All-Steel structures as defined in the different codes, although the present

report contemplates a wider application of this type in point of permissible number of stories and occupancies,

and degrees of fire resistance are specified considerably

above those of unprotected metal members.

As has been previously indicated, light wood interior construction, by the application of firestopping and

suitable finishes, can be made fully as fire resistive as heavy timber construction. Hence, buildings having

exterior masonry walls and light or heavy interior wood

or other non-fire-resistive framing (Classes 3 and 6, New York; Types III and IV, Boston and Denver; Types 2 and 4, Minneapolis; Types Ha and lib, Atlanta; and Mill and Ordinary Masonry, Seattle) can be placed in one group defined herein as Exterior- Protected. This leaves structures defined as Frame

or Wood Frame comprising those classified in this report under Wood Construction.

2. Occupancy Classifications

In the Seattle code there are no occupany classifica- tions and in the other codes there are from three to ten with two or three subdivisions within some of them.

It appears that if an occupancy classification is to serve

its purpose, each class should not cover too wide a

range in conditions otherwise general requirements

applied from the occupancy standpoint may not be

equitable for the whole range. There can be little objection to the more detailed classifications from the standpoint of clarity and enforcement, since the name

of the occupancy serves in large part as a definition and

other defining conditions can be readily applied. In the present report, data are given by means of which the fire hazard as it concerns fire effects on struc- tural members can be defined in terms of the combustible content of buildings, and this is indicated as having a general relation to the kind of occupancy

involved. However, the hazard to occupants is not

thus as well defined since this depends in part on the flammability as well as the amount of combustibles

and on the number, distribution, age, and physical condition of the occupants. Hence, it is believed that

restrictions can be best applied in relation to occupancy when the latter is defined in as much detail as is deemed

practical for building code purposes.

3. Fire Zoning

While up to four fire zones, including the unrestricted

area, are established by these codes, in no case do the

restrictions on construction for the first fire zone go as

far as justified for the congested high-value districts in our large cities, where Fireproof construction might be

required except for small buildings of types herein defined as Incombustible or Exterior-Protected. For

other than the larger cities, such rigid restrictions may

not be justified, any distinction between requirements

for the first and second fire zone, as exemplified in these

codes, being in the extent to which unprotected metal

and wood construction are permitted. Except as may

be deemed necessary on account of variations in the geographic or other features of the area covered, there appears to be little need for establishing more than

three fire zones, inclusive of the outer or unrestricted

area.

4. Spacing from Adjacent Construction or Property Line

It is noted that restrictions of this type while differing

widely are based on both type of construction and

occupancy. In some cases the location of small buildings, such as private garages, is less restricted than of large buildings.

5. Height and Area Limitations

Only in the Atlanta code is there a general height

limitation (150 ft) applied to buildings of the Fireproof

type where also areas are limited to 10,000 to 40,000

ft 2 for some occupancies. In Seattle the height except

for towers is limited to two and one-half times the width

of the widest street on which the building abuts and for some commercial occupancies further height limitations and also area limitations are applied. In Boston the

height of hazardous commercial buildings of the Fire- proof type is limited to 150 ft and the area to 15,000

to 20,000 ft 2

. In Minneapolis the floor areas in Fire- proof buildings over one story in height are limited to

[67]
30,000 to 83,000 ft 2

, depending on the number of street frontages and installation of automatic sprinklers. In New York and Denver no height or area restrictions are applied for this type of construction except as may

be required by zoning regulations.

The limitations applied to the Incombustible (Metal,

Metal Frame, All Steel) type present a wider range and

in general are more restrictive than might be considered

necessary, particularly if some degree of protection is applied to the metal members. For the other types

the requirements are more uniform due apparently in part to more definite type definitions. The heights

and areas permitted in some codes for buildings of the Exterior-Protected type appear excessive, and considering available materials and constructions such

concessions can hardly be regarded as necessary under

normal conditions.

6. Permissible Materials

While for the Fireproof type the structural members

are required to be of incombustible materials, there is a wide range in materials permitted for trim, finish, and

partitions. According to some of the codes these can be of combustible materials to an extent that offsets largely the basic safety features of the construction. There are notable deviations as concerns the other types

of construction although here also differences in per- missible materials and their method of application materially affect the status of the building type in its re- lation to fire safety. Without doubt, practical considerations and the prevailing building practices keep

these variations within closer limits than indicated by

comparison of the codes.

7. Required Fire Resistance

Whether given in the form of thickness of protecting materials or as periods of fire resistance referenced to the standard furnace test, the code requirements are the same for a given type of construction without refer- ence to the occupancy or associated amounts of combustibles. The 4-hr requirement for exterior walls can

be regarded as excessive as a general restriction, and

the same holds for party and fire walls for all but cer- tain commeicial occupancies, for which without further provisions it may be insufficient. The fire resistance required for incombustible members in buildings per- mitted to have interior wood framing is generally in excess of that obtainable with the latter. In some of the codes the requirement for protection of shafts and

exit ways is far in excess of that required for safe exit of occupants in point of fire resistance, but not necessarily as concerns smoke-tightness.

8. Permissible Occupancies

The restrictions as to permissible types of construction to accommodate given occupancies are supplemented by height and area limitations, also partly

based on occupancy. Distinctions are necessarily

largely based on judgment aided by such experience as

is applicable. The general limitation of the larger

places of public assembly and of detention buildings to those of Fireproof construction appears warranted by

the fire record.

[68]
APPENDIX B. METHODS OF ESTIMATING FIRE-RESISTANCE PERIODS

Section 1. General Method of Estimating the

Ultimate Fire-Resistance Periods of Walls

and Partitions

In most cases the fire-resistance period will be de- termined by the temperature rise on the unexposed side of the wall, and it is on this criterion that the following

method of interpolation and extension is based. According to the general theory of heat transmission,

if walls of the same material are exposed to a heat source that maintains a constant temperature of the surface of the exposed side, and the unexposed side is protected

against heat loss, the time at which a given temperature

will be attained on the unexposed side will vary as the square of the wall thickness. (See "Heat Transmission" by Wm. H. McAdams (1933) and "Mathematical

Theory of Heat Conduction" by Ingersoll and Zobel

(1913).) In the standard fire test, which involves specified conditions of temperature measurement and a fire that

increases the temperature at the exposed surface of the

wall as the test proceeds, the time required to attain a

given temperature rise on the unexposed side will be

different from where the temperature on the exposed

side remains constant at the initial exposure temperature for any period. It has been found that comparisons fairly consistent with test results can be obtained

by assuming the variation to be according to some lower power of n than the second. The fire resistance of the

wall can be then expressed by the formula

where R =fire-resistance period, c= coefficient depending on the material, design of wall, and the units of measurement

of R and V, V—volume of solid material per unit area of wall

surface, and

n=exponent depending on the rate of increase

of temperature at the exposed face of the

wall. For walls of a given material and design it was found

that an increase of 50 percent in volume of solid material per unit area of wall surface resulted in a 100-per- cent increase in the fire-resistance period. 1 This rela- tion gives a value of 1.7 for n. The lower value for n

as compared with 2 for the theoretical condition of constant temperature of the exposed surface is to be ex- pected as the rising temperature at the exposed surface would tend to shorten the fire-resistance period of walls qualifying for relatively higher ratings.

The fire-resistance period of a wall may be expressed

in terms of the fire-resistance periods of the conjoined

wythes or laminae of the wall as follows:

If Rj, R2 , R3, etc. =fire-resistance periods of walls (or component laminae of walls) having volumes of solid material per unit area of wall surface of Vu V2 , Vs , etc., respectively, also letting c and n be as defined above, then for walls in general,

fii=(c,F,)«, fl,= (e»Vi)», and R3 =(c3 V3 )». The fire-resistance period of the composite wall will be

R-(cV)n

, where V=Vi+V2 +V3 and c= 0V1±c^+c^y

Therefore, R = (c, F, + c2 V2 + c3 V3) " = CRI v»+B2i/»+JR3i/»)'\

Substituting 1.7 for n and 0.59 for 1/n, the general

formula becomes

JB=(i?1 o.59 +jK2o.59_|_fl3o.s9

_ etc.) 1 - 7

It will be noted that the fire-resistance period has been expressed in terms of the fire-resistance periods of the component laminae of the wall, which need not

be of the same material and design. For walls otherwise similar but of different thickness the general formula takes the following form: R2 =Rl(y?) »

where Vi and V2 are the respective volumes of solid materials per unit area of wall surface, and R2 and Ri

the corresponding fire-resistance periods.

If the fire-resistance period of a wall is known and if it is desired to find the fire-resistance period when one

coat of J^-in. 1:3 sanded gypsum plaster is added, the

solution is as follows: ^ = (^ 1 0.59 + O_ 3)1.7_ Ri=fire-resistance period of the unplastered wall

in hours; R —fire-resistance period of the plastered wall in hours

;

0.3 = an average value derived from tests (use 0.6 if plastered on both sides). Use 0.37 for one coat of 5/8-in. 1:3 sanded gypsum

plaster and 0.75 if plastered on both sides. For %-in. thickness of this plaster, use 0.45 for application on

one side and 0.90 for plaster on both sides. The value

of the constant is directly proportional to the thickness

of plaster. In like manner, it was found that the effect of con- tinuous air spaces separating wythes. or laminae of a

wall by distances of l/2 to 3}i in. may be estimated by

the use of the values 0.3 and 0.6 for one and two spaces,

respectively.

Section 2. General Method of Estimating the

Ultimate Fire-Resistance Periods of Columns

According to theory, if similar homogeneous columns

of the same material are exposed to a heat source that maintains a constant temperature at the surface of the column, the time at which a given temperature at the

center of the column is attained will vary as the square

of the distance from the surface to the center, or di- rectly as the transverse area of the section. Although

1 This also corresponds with findings of Menzel, see page 26.

[69]
the temperature at the center of the column is not the

criterion for determining its ultimate fire resistance, the above theoretical consideration lends support to the

conclusion that a substantial increase in fire resistance is to be expected, when the total area of solid material in the transverse section is increased.

(a) Protected Metal Columns

The fire resistance of protected metal columns, by

analogy with the principles applied above for walls, can be expressed approximately by the following formula: R={FVn +fl, n) n

t (!) where R is the fire resistance of the column, F is the fire resistance attributable to the portion of the protection

outside of the lines circumscribing the metal section (outside section), and /is that attributable to the portion within the lines circumscribing the metal section

(inside section)

.

The fire resistance of columns as for walls can be as- sumed to be a function of the volume of solid material per unit area of outside or fire-exposed surface. The

constants for the "outside" and "inside" sections of pro- tected metal columns can, however, not be taken to be

the same, and accordingly on the above basis, formula 1 may be written in the form:

or R = c(D-a^\ (3)

where c and a are constants, and D and d are sides or diameters of "outside" and "inside" sections, respectively. As concerns results from fire exposure in the standard furnace test, n can be taken as 1.7. The other two constants can be obtained by solution of one or more pairs of simultaneous equations obtained from re- sults of fire tests of two or more columns of the same

material and of similar but unequal sections. With constants thus derived, the formula can be used to inter- polate and extend within moderate limits the results of

fire tests with a given type of column and protection.

It will be used only in the case of structural steel col- umns with solid concrete protections and all reentrant spaces filled with the concrete. For this condition, a, was found to be 0.4, and c varied with the coarse aggregate used. Accordingly, for structural steel columns

with solid protections of concrete, formula 3 becomes:

R = c(D-0A^y 7 (4)

(£>) Reinforced Concrete Columns

Tests to failure of reinforced concrete columns were

limited to columns having fire-resistance periods of less than 4 hr for concrete made with siliceous aggregate and

about 7 hr for trap-rock concrete. The columns made

with calcareous aggregate concrete and some made with

trap-rock aggregate were not tested to failure under the working load and fire exposure, the tests being ter- minated at 4 or 8 hr. It was found that formula 3, using the same values of c and a as determined for

structural steel protected solidly with concrete, could be

applied consistently to the results of fire tests of concrete columns. For this purpose d was taken as the diameter or side of the column core. Accordingly, in the case of working loads computed as carried by the

core area (which was the method used for the columns

tested), the interpolations and extensions were made

by the use of formula 4 above. However, according to present practice, except as it concerns columns heavily reinforced with bands or spiral

hooping, the working load is generally computed on the

basis of the gross area of the column. This will have the

effect of increasing the permissible load on a column of a given size with consequent decrease in its fire resist- ance. An approximate allowance for Jhis can be made

by assuming d to be equal to D.

Accordingly, formula 4 for this condition becomes:

R = c(0.6Dyi. (5) Section 3. Applications Made in the Present

Report

Some applications were made of the above methods

as limited interpolation and extension of related test data, which are noted under ratings for load-bearing

masonry walls (p. 26), masonry partitions of structural

clay tile and hollow concrete units (p. 30) , plaster parti- tions (p. 32), and columns (p. 38). Many of them

involve increases in fire resistance due to plaster, allow- ances for which have been generally made in other compilations of fire-resistance ratings. By the present, method the constant representing the increment is added to the 1.7 root of the rating for the unplastered

construction and the sum raised to the 1.7 power to give the rating for the plastered construction. This

represents a more rational method than a fixed addition

to the rating for the unplastered condition and conforms

with results of fire tests that indicate quite uniformly an increase in the increment due to plaster with increase

in fire rating of the unplastered construction. In general, the limit to which applications of the methods were made was set by average variations to be expected in results of fire tests of nominally comparable constructions. Accordingly, conservative extension and interpolation of a related line of test data are considered as giving reliability at least comparable to that obtaining for results of individual fire tests. Variability for the latter has been indicated to be as high as 40- to 50-percent deviation from average values,

with 5- to 15-percent deviation representing more

nearly the average experience. The variability is caused by variations in material, workmanship, and

seasoning conditions, such as quality, set, and seasoning

of plaster and cement, varying imperfections of joints

in masonry, and amount of free water present in the construction at the time of test. The latter is a fre- quent cause of variation, depending as it does, not only on surface volume-relations and seasoning conditions,

but also on the moisture-retentive properties of the

materials. Washington, June 9, 1942.

[70]
BUILDING MATERIALS AND STRUCTURES REPORTS

[Continued from cover page II] BMS38 Structural Properties of Two "Dunstone" Wall Constructions Sponsored by the W. E. Dunn Manufacturing Co 100 BMS39 Structural Properties of a Wall Construction of "Pfeifer Units" Sponsored by the Wisconsin Units Co . 100 BMS40 Structural Properties of a Wall Construction of "Knap Concrete Wall Units" Sponsored

by Knap America, Inc 100 BMS41 Effect of Heating and Cooling on the Permeability of Masonry Walls 100 BMS42 Structural Properties of Wood-Frame Wall and Partition Constructions with "Celotex"

Insulating Boards Sponsored by The Celotex Corporation 150 BMS43 Performance Test of Floor Coverings for Use in Low-Cost Housing: Part 2 100 BMS44 Surface Treatment of Steel Prior to Painting 10(5 BMS45 Air Infiltration Through Windows 100 BMS46 Structural Properties of "Scot-Bilt" Prefabricated Sheet-Steel Constructions for Walls,

Floors, and Roofs Sponsored by The Globe-Wernicke Co 100 BMS47 Structural Properties of Prefabricated Wood-Frame Constructions for Walls, Partitions, and Floors Sponsored by American Houses, Inc 10)5 BMS48 Structural Properties of "Precision-Built" Frame Wall and Partition Constructions

Sponsored by the Homasote Co 100 BMS49 Metallic Roofing for Low-Cost House Construction 100 BMS50 Stability of Fiber Building (Boards as Determined by Accelerated Aging 100 BMS51 Structural Properties of "Tilecrete Type A" Floor Construction Sponsored by the

Tilecrete Co 100 BMS52 Effect of Ceiling Insulation upon Summer Comfort 100 BMS53 Structural Properties of a Masonry Wall Construction of "Munlock Dry Wall Brick"

Sponsored by the Munlock Engineering Co 100 BMS54 Effect of Soot on the Rating of an Oil-Fired Heating Boiler 100 BMS55 Effects of Wetting and Drying on the Permeability of Masonry Walls 100 BMS56 A Survey of Humidities in Residences 100 BMS57 Roofing in the United States—Results of a Questionnaire 100 BMS58 Strength of Soft-Soldered Joints in Copper Tubing 100 BMS59 Properties of Adhesives for Floor Coverings 10(5 BMS60 Strength, Absorption, and Resistance to Laboratory Freezing and Thawing of Building

Bricks Produced in the United States 150 BMS61 Structural Properties of Two Nonreinforced Monolithic Concrete Wall Constructions-. 100 BMS62 Structural Properties of a Precast Joist Concrete Floor Construction Sponsored by the Portland Cement Association 10(5 BMS63 Moisture Condensation in Building Walls 100 BMS64 Solar Heating of Various Surfaces 10(5 BMS65 Methods of Estimating Loads in Plumbing Systems 10(5 BMS66 Plumbing Manual 20(5 BMS67 Structural Properties of "Mu-Steel" Prefabricated Sheet-Steel Constructions for Walls,

Partitions, Floors, and Roofs Sponsored by Herman A. Mugler 15(5 BMS68 Performance Test of Floor Coverings for Use in Low-Cost Housing: Part 3 150 BMS69 Stability of Fiber Sheathing Boards as Determined by Accelerated Aging 100 BMS70 Asphalt-Prepared Roll Roofings and Shingles 15(5 BMS71 Fire Tests of Wood- and Metal-Framed Partitions 20(5 BMS72 Structural Properties of "Precision-Built, Jr." Prefabricated Wood-Frame Wall construction Sponsored by the Homasote Co 10(5 BMS73 Indentation Characteristics of Floor Coverings 10(5 BMS74 Structural and Heat-Transfer Properties of "U. S. S. Panelbilt" Prefabricated SheetSteel Constructions for Walls, Partitions, and Roofs Sponsored by the Tennessee

Coal, Iron, and Railroad Co 150 BMS75 Survey of Roofing Materials in the North Central States 150 BMS76 Effect of Outdoor Exposure on the Water Permeability of Masonry Walls 15(5 BMS77 Properties and Performance of Fiber Tile Boards 10(5 BMS78 Structural, Heat-Transfer, and Water-Permeability Properties of Five Earth-Wall Constructions 200 BMS79 Water-Distributing Systems for Buildings 15(5 BMS80 Performance Tests of Floor Coverings for Use in Low-Cost Housing: Part 4 15(5 BMS81 Field Inspectors' Check List for Building Construction, (cloth cover, 5 x 7}i inches) 200 BMS82 Water Permeability of Walls Built of Masonry Units 20(5 BMS83 Strength of Sleeve Joints in Copper Tubing Made with Various Lead-Base Solders 100 BMS84 Survey of Roofing Materials in the South Central States 15(5 BMS85 Dimensional Changes of Floor Coverings with Changes in Relative Humidity and

Temperature 10(5 BMS86 Structural, Heat-Transfer, and Water-Permeability Properties of "Speedbrik" Wall Construction Sponsored by the General Shale Products Corporation 15(5 BMS87 A Method for Developing Specifications for Building Construction—Report of Subcommittee on Specifications of the Central Housing Committee on Research, Design and

Construction 10(5 BMS88 Recommended Building Code Requirements for New Dwelling Construction with

Special Reference to War Housing 100 BMS89 Structural Properties of "Precision-Built, Jr." (Second Construction) Prefabricated Wood-Frame Wall Construction Sponsored by the Homasote Co 150 BMS90 Structural Properties of "PHC" Prefabricated Wood-Frame Constructions for Walls,

Floors, and Roofs Sponsored by the PHC Housing Corporation 150 BMS91 A Glossary of Housing Terms 150 BMS92 Fire-Resistance Classifications of Building Constructions 150