U. S. DEPARTMENT OF COMMERCE

BUREAU OF STANDARDS

RECOMMENDED

I MINIMUM REQUIREMENTS

FOR SMALL DWELLING

CONSTRUCTION

BUILDING AND HOUSING PUBLICATION No. 18

U. S. DEPARTMENT OF COMMERCE

ROY D. CHAPIN, Secretary BUREAU OF STANDARDS

LYMAN J, BRIGGS, Acting Director

Building and Housing Publication No. 18

Supersedes BHl, Report of July 20, 1922 RECOMMENDED MINIMUM REQUIREMENTS

FOR

SMALL DWELLING CONSTRUCTION

REPORT OF THE

DEPARTMENT OF COMMERCE

BUILDING CODE COMMITTEE

WILLIAM K. HATT, Chairman ALBERT KAHN WILLIAM ARTHUR PAYNE RUDOLPH P. MILLER H. L. WHITTEMORE

JOHN A. NEWLIN JOSEPH R. WORCESTER GEORGE N. THOMPSON, Secretary

JAMES S. TAYLOR, Chief, Division of Building and Housing Bureau of Standards, Department of Commerce

UNITED STATES

GOVERNMENT PRINTING OFFICE WASHINGTON ; 1932

For sale by the Superintendent of Documents, Washington, D. C, Price 10 cents
MEMBERSHIP OF THE BUILDING CODE COMMITTEE

OF THE DEPARTMENT OF COMMERCE

WrLLiAM K. Hatt, chairman ; professor of civil engineering and director,

Laboratory for Testing Materials, Purdue University; member, American . Society of Civil Engineers ; American Concrete Institute ; American Society ! for Testing Materials. : Albert Kahn, architect, Detroit, Mich. ; fellow, American Institute of ; Architects. 'j Rudolph P. Miller, consulting engineer. New York City ; past president, ; Building Officials’ Conference ; member, American Society of Civil Engineers ; , American Institute of Consulting Engineers ; American Society for Testing

Materials. : John A. Newlin, in charge of section of timber mechanics. Forest Products

Laboratory, Forest Service, United States Department of Agriculture, Madi- , son, Wis. ; member, American Society for Testing Materials ; American

Society of Civil Engineers.

William Arthur Paynel vice president, Charles T. Wills (Inc.), Building

Construction, New York City; vice president. New York Building (’ongress. , II. L. Whittemore, chief of the engineering mechanics section of the Bureau

of Standards ; manager. American Society of Mechanical Engineers ; member,

American Society for Testing Materials; American Association of Engineers;

American Welding Society.

Joseph R. Worcester, consulting engineer, Boston, Mass. ; member. American^

Society of Civil Engineers ; American Institute of Consulting Engineers.

George N. Thompson, secretary.
CONTENTS

i PART 1.—INTRODUCTION

Page

j Origin and purpose of the Building Code Committee 1

I Importance of sound building regulations 2 Report covers construction of small dwellings only 3

i Object of recommendations 3

I'i Adequate enforcement essential 3

: Recommendations advisory 3 Acknowledgment of assistance 3

} PART 2.—MINIMUM REQUIREMENTS FOR SAFE AND ECONOMICAL CONSTRUCTION

OF SMALL DWELLINGS

Sec. 1. General requirements

Sec. 1-1. Definitions

Sec. 1-2. Limitations

Sec. 1-3. Heights

Sec. 1-4. Loads

Sec. 1-5. Floor loads

Sec. 1-6. Roof loads

Sec. 1-7. Roof anchorage

Sec. 2. Foundations

Sec. 2-1. Footings

Sec. 2-2. Foundation walls

Sec. 2-3. Basement columns

! Sec. 2-4. Ventilation

' Sec. 3. Dwellings having solid brick walls

Sec. 3-1. Qualit}' of brick and mortar

I Sec. 3-2. Thickness, height, and bonding of exterior walls

Sec. 3-3. Piers

Sec. 3-4. Cliases

Sec. 3-5. Arches and lintels Sec. 3-6. Wood inserts in masonry walls

Sec. 4. Dwellings having walls of hollow masonry units or hollow walls of brick

f Sec. 4-1. Quality of materials

Sec. 4-2. Thickness, height, and bonding of exterior walls

I Sec. 4-3. Piers

Sec. 4—4. Bearing for concentrated loads

* Sec. 4-5. Chases

Sec. 4—6. Arches and lintels Sec. 4r-7. Wood inserts

Sec. 5. Concrete dwellings of monolithic, unit, or structural frame type__

Sec. 5-1. Quality of materials

Sec. 5-2. Thickness, height, and bonding of exterior walls

Sec. 5-3. Piers

Sec. 5-4. Chases

Sec. 5-5. Arches and lintels

' Sec. 5-6. Unit construction

Sec. 5-7. Concrete structural frame with inclosing walls

Sec. 5-8. Concrete floors, floor beams, and columns

J

Sec. 6. Wood frame construction - Sec. 6-1. Exterior walls t Sec. 6-2. Masonry veneer on wood frame construction

] Sec. 6-3. Stucco on frame construction

r m

5

56

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6

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7

7

77

78

88

8

8

99

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910

10

10

1111

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1112

1212

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12

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13

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1314
IV CONTENTS

Page

Sec. 7. Wood framing X4

Sec. 7-1. General requirements 14

Sec. 7-2. Strength of members 14

Sec. 7-3. Sills, Joists, girders, and rafters 16

Sec. 7-4. Bearing partitions ~ 16

Sec. 7-5. Nonbearing partitions 17

Sec. 8. Metal frame construction 17

Sec. 8-1. Construction 17

Sec. 9. Party walls, partitions, and ceilings 17

Sec. 9-1. Party walls 17

Sec. 9-2. Ceilings 18

Sec. 9-3. Parapet walls 18

Sec. 9-4. Interior partitions 18

Sec. 10. Miscellaneous 19

Sec. 10-1. Chimnej'S and fireplaces 19

Sec. 10-2. Combustible construction around chimneys and fireplaces. 21

Sec. 10-3. Heating appliances 22

Sec. 10-4. Fire stopping 23

Sec. 10-5. Private garages combined with dwellings 24 PART 3.—APPENDIX

Par. Purpose 26

1. Heights and areas 26

2. Weights of materials 27

3. Quality of materials ; 28

4. Simplification of dimensions 29

5. Floors 29

6. Roof loads 30

7. Soil pressures 30

8. Foundation walls 30

9. Bearing for foundation walls 31

10. Provision for air circulation 32

1 1 Piprs? 12. Quality of brick 32

13. Quality of mortar 33

14. Thickness, height, and bonding of solid brick exterior walls 34

15. Conclusions on 8-inch walls 36

16. Advantages of 12-inch walls recognized 36

17. Durability and weathering of brick masonry 36

18. Laying of brick 37

19. Quality of hollow masonry units 37

20. Exterior masonry walls of hollow units 38

21. Hollow walls of brick 39

22. Laying structural clay tile (hollow building tile) 39

23. Concrete 41

24. Construction methods for concrete houses 41

25. Concrete houses with monolithic walls 42

26. Concrete houses of unit construction 42

27. Structural concrete frame with light inclosure or panel walls 42

28. Masonry veneer on frame construction 43

29. Stucco construction 44

30. Sizes of timber and lumber 46

31. Removal of overloads on timber construction 47

32. Bearing values for joists 51

33. Explanation and comments relative to table on girder factor and max- imum permissible lengths of floor joists 51

34. Flooring 52

35. Notes bearing on the use of lumber and timber in small dwelling construction 52

36. Lumber grade marking 64

37. Metal construction 64

38. Termite protection 66

39. Rat proofing 70

40. Plaster and other waU coverings 70
CONTENTS V

Page

41. Preparation of base for plaster 71

42. Plaster materials 72

43. Mixing and application of plaster 73

44. Number and thickness of plaster coats necessary ”1 75

45. Furring 75

46. Insulation ~~ 77

47. Party walls 73

48. Parapet walls 79

49. Roof coverings 79

50. Chimneys 79

51. Heating appliances 39

52. Fire resistive requirements 91

53. Importance of fire stops 93

54. Vigilance necessary to secure fire stops 94

55. Fire stopping materials 94

56. Garage consHuction 99

57. Developments in construction 101

58. Plumbing 102

59. Electrical requirements 102

60. Value of publications 102 TABLES

Page

1. Mlowable stresses permissible for structural timbers in small dwellings. 15

2. Girder factor and maximum permissible length of fioor joists 48

3. Maximum permissible unsupported lengths of rafters measured from

plate to ridge 50

4. Results of tests of panels without window and door openings 62

5. Results of tests of jjanels with window and door openings 63

6. Approximate fuel savings in dwelling houses 78

Fig.

1 . 2. 3.

4.5.6. 7.8. 9. 10. 11 . 12. 13. 14.

15.

16.

17. 18.

19. 20. 21 . 22. 23.

ILLUSTRATIONS

Comparison of desirable and undesirable footings for foundation walls and basement columns 31

Details of joist seating in solid brick and hollow tile walls 35

Details of 8-inch hollow waU of brick (all rolock), illustrating best methods of joist support 39

Details of faced walls 40

Details of construction for brick veneer on frame backing 44

Desirable methods of framing around stairway openings 52 Approved details of balloon frame construction 53 Common defects in balloon frame construction 54 Braced-frame construction 55 Common defects in braced-frame construction 56

Details of platform-frame type of construction 57

Details of sill construction ^ 58 Comparison of desirable and undesirable framing around window

openings 64 Comparison of well and poorly built window frames, showing methods

of excluding air and moisture 65 Faulty frame which will result in uneven settlement of structure _ 66 Framing to bring about equal settlement of partitions and exterior walls of structure 7--- 67

Comparison of proper and improper framing over wall and partition

openings 68

Methods of installing piping without damage to tinaber frame 69

Methods of securing backing for lath where partitions meet frame

walls at or between studs ^4 Methods of installing gypsum wall board

Elevation and section of an interior independent chimney showing

recommended construction _ ^ Details of recommended chimney construction, showing flashing 82

Details of chimney construction at floor and roof 83
VI CONTENTS

Fig. Page

24. Details of recommended fireplace construction for inside chimneys... 84

25. Details of recommended fireplace construction outside chimney 85

26. Details of recommended fireplace and chimney construction with

structural clay tile (hollow building tile) 86

27. Typical sections of recommended chimney construction, showing

details of wood framing about chimneys 87

28. Details of effective area of flue finings 88

29. Fire stopping for masonry walls at floor and roof fines 95

30. Details of fire stopping over basement walls and partitions 96

31. Details of fire stopping for frame walls at fine of upper floor joists 97

32. Fire-stopping details for interior partitions 98

33. Details of fire stopping around w^arm-air pipes and floor registers 99

34. Fire-stopping details for cornices in wood frame construction 100
LETTER OF SUBMITTAL

Washington, D. C., March 31^ 1932.

Hon. R. P. LaMONT,

Secretary of Commerce.^ Washington., D. C,

Sir : The report of the Building Code Committee, entitled

“ Recommended Minimum Requirements for Small Dwelling Construction,” first issued in 1922, has been revised in accordance with

present-day conditions and is herewith submitted with the recom- mendation that a new edition be printed for public distribution.

Since the publication of the first edition interest in safe and

economical building construction has been intensified. Last year

the President's Conference on Home Building and Home Ownership, under the leadership of Secretary Wilbur and yourself, met

and called attentioii to the manifold problems associated with dwelling construction. Building regulations have been mentioned by

several of its committees as deserving careful scrutiny. The Building Code Committee has been accumulating information bearing on

the subject and welcomes the opportunity to cooperate by supplying

revised suggested reciuirements. It has made a careful review of its earlier recommendations with special attention to construction developments that may be just over the horizon.

xis before, an appendix useful to enforcing officials and to owners and builders of dwellings, generally, is included. This feature has

proved of great value in the past, for better and more economical

construction is to be hoped for not only through legal requirements

but also through education.

Very truly yours,

Wm. K. Hatt,

Chairman., Building Code Committee. vn
LETTER OF ACCEPTANCE

Department of Commerce,

Office of the Secretary,

Washington^ May 28^ 1932.

Dr. William K. Hatt,

Chairman Building Code Committee.,

Department of Commerce. Dear Doctor Hatt: It is a great pleasure for me to receive the

manuscript for the revised edition of the Building Code Committee’s

report on Recommended Minimum Requirements for Small Dwelling Construction, which the Building Code Committee has

thoroughly revised and brought up to date. There is a common tendency to forget the positive protection to safety and health whicli j)roperly framed, well-administered building codes can effect through ])rohibiting faidty structures. This

tendency has been due in large measure to the hani])ering effects of

anti(iuated codes which unnecessarily restrict the develo])nient and

use of many of the best improvements in materials and methods that

have been made in recent years. The prominent ])art played by the earlier edition of your committee’s recommended small-dwelling requirements has already done

much to bring about progressive changes. Your work has thereby

hel])ed to reduce costs and assure better quality of construction.

These, your latest recommendations, should greatly assist local code

committees in framing and revising codes and encourage uniformity

in their requirements.

The report, as in the case of the earlier edition, should have an

extensive circulation, and thus be of widespread use to commercial

builders, designers, home owners, and other groups. By thus helping to lay the groundwork for a sound revival of small-home building. its timely value to the xVmerican people should be multiplied.

Your committee has established an enviable reputation for itself as a group of disinterested experts intent on ])roducing rational suggested requirements that combine safety with economy. In accepting the present report I am again reminded of the public benefit

that accrues through your labors.

Very sincerely,

R. P. Lamont.

VIII
RECOMMENDED MINIMUM REQUIREMENTS FOR

SMALL DWELLING CONSTRUCTION

This report is a revision of another bearing the same title and

issued in It is subdivided into three general headings, as follows

:

Part 1.—Introduction: Covering a general description of the cir- cumstances leading to formation of the committee and outlining

its method of procedure and scope of operation.

Part 2.—Minimum Kecpiirements for Safe and Economical Construction of Small Dwellings : Briefly stated, in a form suitable for

incorporation in local ordinances.

Part 8.—Appendix: Containing material not suited to be incorjiorated in a building law but which is supplementary to the vari- ous requirements made in part 2. PART 1.—INTRODUCTION

Tlie circumstances at the time of issuance of the original report

may be summed up in a statement appearing in a preliminary report

of the Senate Committee on Reconstruction and Production ap- pointed in 1920. This committee held extensive hearings and stated

:

The building codes of the country have not been developed upon scientific data but rather on compromise ; they are not uniform in practice and in many

instances involve an additional cost to construction without assuring more

useful or more durable buildings.

The final rej)ort of this Senate committee gave wide publicity to the building code discrepancies long known by architects and building engineers but not fully comprehended by the general public.

Secretary Hoover, of the Department of Commerce, recognizing the

necessity for some central coordinating body to standardize, so far

as possible, the building laws of the country, organized the Building

Code Committee for that purpose. The committee is a part of the

division of building and housing in the Bureau of Standards. This

division has under Avay a broad program of investigation into problems of the building industry.

The committee organized the last of May, 1921, and secured the

appointment of a technical secretary and other clerical assistance;

the task of gathering data on all phases of building regulations was

at once begun, and has gone on as a continuous process since that

time.

The general ])urposes of the committee are as follows

:

1. To study existing building codes and determine the nature of

their disagreement and the extent to which, their requirements are oppressive to the building industry.

1
2 MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS

2. To gather information concerning minimum requirements con- sidered essential by architects and engineers for safe and proper

construction of buildings of different types and varying occupancy,

in an effort to secure safe, economical construction, and eliminate

waste in building.

3. To prepare and publish recommended building regulations

based upon the consensus of reliable information obtained through

various channels of inquiry throughout the country, such recommendations to represent minimum safe practice in all matters pertaining to engineering design and general building methods; these

recommendations to be drafted in such form as to be easily adapted

as amendments to existing building codes or adopted as ordinances

by municipalities which at present have no building laws.

4. To investigate the merits of new building iiiaterials and

methods of construction which promise economy and, so far as it can do so legitimately, to recommend such as appear to have special

merit.

5. Supplemental to the foregoing, the committee may use its influence to further any measures promising improvement in present

methods of building regulation or which encourage building industry.

6. The committee has under consideration the drafting of a complete building code. It believes the main objects desired can be

most quickly and easily secured, however, by recommending standards of practice in those portions of building codes subject to the

greatest general criticism.

The situation in 1921 was rendered especially acute by the great

scarcity of dwellings throughout the country, especiall}^ the small

1 and 2 family type. While this situation is not so pressing at the

time of issuance of this report, there is nevertheless an enhanced

interest in sound and economical construction due to the growing

conviction that home ownership is of deep significance to the welfare

of the country. So strongly has this conviction been impressed

upon responsible civic leaders that more than 3,000 of them came to Washington in December, 1931, for the purpose of evaluating

available facts about home ownership and of stimulating greater

opportunities for its fulfillment. This conference, known as the

President’s Conference on Home Building and Home Ownership,

while recognizing substantial improvement in the building-code

situation, has again emphasized the importance of sound building

.regulations.

The first edition of this report contained a rather extended a])- ])eiidix in which information on good construction going beyond

the limits imjjosed by minimum safe standards was presented. This

Avas done because investigation shoAA^ed that many of the buildings

erected Avhere there Avere no building regulations or no means to en- force existing regulations Avere of sucli loAV-grade construction that

much of the money invested in neAv homes Avas Avasted. The committee felt it could render valuable service by spreading reliable

information concerning sound building practice throughout the

country so that poor building, Avhich is usually the most Avasteful,

may be reduced. Elimination of this most insidious form of loss is believed to be fully as important as the modification of code requirements. Experience haAdng justified this offering of supplementary
MINIMUM SMALI. DWELLING CONSTKUCTION REQUIREMENTS 3

iiiforiiRition as a means of combating low-grade construction, it is continued in the present edition.

The committee has been fortunate in having continuity of service

in dealing with the subject. Four of the seven original members

have participated in the preparation of the revised edition after an

interval of some 10 years. Death has removed Ira H. Woolson,

the first chairman, and Edwin H. Drown. The committee wishes to pay tribute to the untiring interest and enthusiasm which was manifested by these members and which has left its imprint in the report

as it now stands.

The report deals only with construction of dwellings intended for

the occupancy of one and two families between exterior or party

walls. Xo recommendations are made as to portion of lot that

buildings may cover, the distances between buildings or between

buildings and lot lines, or the effect upon construction imposed by

such considerations. Lack of reference to these features is not due

to their unimportance, but merely because the committee has con- sidered them beyond the scope of the present report.

It is recognized that the requirements recommended in part 2 constitute, in some particulars, relaxations from those considered advisable for construction of large buildings. The committee believes,

however, that for the simple types of buildings specified, and because

of the need of eliminating all possible waste, the minimum standards

advised are compatible with a due measure of utility and durability

in the structures affected. The objects which the committee had in

view in recommending these regulations were (1) to secure safe and

yet economical construction, (2) to help eliminate waste in home

building, and (3) to reconcile inharmonious and frequently too

restrictive provisions in existing codes.

The recommendations are predicated on the assumption that good

materials and workmanship will be used and all necessary care taken in assembling the various parts of the structures. The committee feels that thorough building inspection is often lacking and

that many unnecessarily rigid code requirements have been adopted

to offset possible laxity in enforcement. In modifying such provisions to reduce cost, therefore, local authorities should insist upon

supervision of construction by an adequate, competent personnel.

It has been called to the committee’s attention that some misunderstanding exists with regard to the legal status of its recommendations. It should be recognized that the committee’s functions are purely advisory. The recommendations can not be considered in

any sense as obligatory, but are issued to make available to those

locally responsible for exercise of the police power the latest and

most reliable information on building regulation for the class of

buildings considered.

In the preparation of the revised report the committee has had the

advantage of accumulated information supplied through many architects, engineers, contractors, local building officials, representatives

of manufacturing organizations, and others during its period of

existence. In particular, it acknowledges its indebtedness to experts

of the Bureau of Standards. H. B. Houghton, associate engineer

in this bureau, has been of especial assistance in compiling necessary

information and drafting proposed requirements. The committee
4 MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS

lias reviewed available data and has endeavored to see not only that

the present report is up to date, but that it does not discourage the

introduction of new materials at present just over the horizon.

The committee also desires to acknowledge the courtesy of the

following organizations in furnishing cuts with which the appendix

of the report is illustrated: 1 and 2 of Figure 2 were furnished by

the American Face Brick Association; 3 of Figure 2 by the Structural Clay Tile Association; Figure 3 by the Common Brick Manufacturers’ Association of America ; Figure 20 by the Gypsum Association; Figures 1, 6, 13, 14, 15, 16, IT, 18, and 19 by the Weyerhaeuser Forest Products; and Figures 21, 22, 24, 26, 27, 28, 29, 30, 31,

32, 33, and 34 by the National Board of Fire Underwriters,
PART 2 .—MINIMUM REQUIREMENTS FOR SAFE

AND ECONOMICAL CONSTRUCTION OF SMALL

DWELLINGS RECOMMENDED BY THE BUILDING CODE COMMITTEE OF THE DEPARTMENT

OF COMMERCE

SECTION 1. GENERAL REQUIREMENTS

Section 1-1. Definitions.

Approved.—As applied to a material, device, mode of construction, or testing agency, means approved by the building official under

the provisions of this code, or by other authority designated by law

to give approval in the matter in question.

Bearing waU.—A wall which supports any vertical load in addition to its weight.

Dead loads.—The weight of walls, floors, roofs, partitions, and

otlier permanent portions of the structure. Dwelling.—A building occupied exclusively as a residence for one

or two families, or as a boarding or rooming house serving not more

than 15 persons with meals or sleeping accomodations, or both.

Faced icall.—A masonry wall, the facing and backing of which are

so bonded that they act together in sustaining the load.

Fire door.—A door construction consisting of door, frame, and sill, which under approved fire-test conditions meets the requirements for

the location in which it is to be used.

Grade.—For buildings, adjoining one street only, the elevation of

the sidewalk at the center of that wall adjoining the street. For buildings adjoining more than one street, the average of the

elevations of the sidewalk at centers of all walls adjoining streets. For buildings having no wall adjoining the street, the^ average

level of the ground (finished surface) adjacent to the exterior walls

of the building. All walls approximately parallel to and not more

than 5 feet from a street line are to be considered as adjoining a

street.

' Height— height of a wall is the vertical distance measured

from the highest point of the wall to the top of the foundation wall

;

the height of a building is the vertical distance from the grade line to the highest point of the building.

Lintel.—A structural member supporting masonry above an opening in a wall or partition.

Live loads.—All loads except dead loads.

Masonry.— brick, concrete, structural clay tile (hollow tile), concrete block or tile, gypsum block, or other similar building units or materials or a combination of same, bonded together with mortar

to form a wall, pier, or buttress. . , , . i i

. Metal frame.—yiAA frame construction is that in which struc- tural parts are of metal or dependent on a metal frame tor suppor ,
6 MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS

and in which the structural members are not required to meet ordinary standards for fire-resistive protection. . ^ Nonbearing wall.—A wall which supports no load in addition to

its own weight.

Party wall.—A wall used or adapted for joint service between

two buildings.

Pier.—A bearing wall having a horizontal cross section not exceeding 4 square feet and not bonded at the sides into adjoining masonry.

Plain concrete.—Concrete containing not more than two-tenths of

1 per cent of reinforcement.

Private garage.

A building or a portion thereof in which motor

vehicles are stored or kept, and whose area does not exceed 500 square

feet. * Reinforced concrete.—Concrete containing more than two-tenths

of 1 per cent .of reinforcement and in which the reinforcement is so embedded that the two materials act together in sustaining the load.

Veneered wall.—A wall having a facing which is not attached and

bonded to the backing, so that they act together in sustaining the

load.

Tkood frame.—Wood frame construction is that in which struc- tural parts and materials are of wood or are dependent upon a wood

frame for support, including construction having an incombustible

exterior veneer.

Sec. 1-2. Limitations.

These requirements shall apply only to buildings used as dwellings, either detached, semidetached, or in rows, and intended for the

occupancy of not more than two families in each Unit. (The restrictions, limitations, and tabulations apply to small dwellings only,

and are not to be considered as general for or applicable to other and larger

types of construction. The recommendations are in no sense a housing code or tenement-house law in the ordinary acceptance of these terms ; neither do

they take into consideration regulations in regard to tire limits or congested

mercantile districts or types of construction that should or should not be used because of exterior tire risks. See introduction, p. 3.) Sec. 1-3. Heights.

The number of stories in dwellings shall be limited only by the

permissible height of the walls, provided that for masonry wall and

joist construction such height shall not exceed 45 feet and not more

than three stories shall be allowed within this height, and provided

further that for frame construction the height shall not exceed 40

feet and shall have not more than two and one-half stories. (See

Appendix, par. 1.) Sec. 1-4. Loads.

All parts of dwellings shall be designed to support safely their

own weight and the portion of the live load on floor or roof which

they carry. (See Appendix, par. 2.) Sec. 1-5. Floor Loads.

1. Floors shall be designed to support their own weight, the dead

loads they are to carry, and a live load of at least 40 pounds per

square foot
I MINIMUM SMALL DWELLING CONSTRUCTION BEQUIEEMENTS 7

2. Girders or other nieinbers supporting a floor area not exceeding

100 s(|uare feet shall be designed for a live load of not less than 40

j)Oiinds per square foot uniformly distributed over the floor area. If the floor area exceeds 100 square feet but does not exceed 200

jscpiare feet, such members shall be designed for a live load of not

less than 35 pounds per square foot uniformly distributed over the

floor area. If the floor area exceeds 200 square feet, such members

shall be designed for a live load of not less than 30 pounds per

: square foot. Sec. 1-6. Roof Loads.

.1 Roofs having a rise of 4 inches or less per foot shall be designed to support safely a vertical live load of 30 pounds per square foot of

horizontal projection, applied to any or all slopes. With a rise of

, more than 4 inches and less than 12 inches per foot a vertical live

load of 20 pounds on the horizontal projection shall be assumed. If

the rise exceeds 12 inches per foot, provision shall be made for a wind force acting in a normal direction (on one slope at a time) of

20 pounds per sloping square foot. (See Appendix, par. 6.) Note.—For roof covoriiigs, see Appendix, paragrai)h 49. Sec. 1-7. Roof Anchorage.

Roofs shall be securely attached to the construction on which they

rest. (See sec. 7-3.)

SECTION 2. FOUNDATIONS

(These requirements apply to small dwellings and may not apply to larger

buildings or other types of buildings.) Sec. 2-1. Footings.

Foundation walls shall extend below the frost level and the horizontal area at the bottom shall be such that the safe carrying ca- pacity of the soil is not exceeded. (See Appendix, par. 9.) Sec. 2-2. Foundation Walls.

1. Foundation walls shall be built of stone, brick, concrete (plain,

rubble, or reinforced) , solid or hollow masonry units, or hollow walls

of brick. Materials and mortar for foundation walls shall be at

least equal in (piality in all respects to those required for exterior

bearing walls.

2. Foundation walls shall be of sufficient strength and thickness

to resist lateral pressures from adjacent earth and to support their

vertical loads, provided that in no case shall their thickness be less than the walls immediately above them.

When built of brick, coursed stone, solid or hollow masonry units, or hollow walls of brick the thickness of foundation walls shall be

not less than 12 inches, provided that when such walls do not extend more than 5 feet below the adj acent ground level the minimum thick- ness of solid brick, solid masonry units, or coursed stone walls may

be 8 inches if included within the allowable height of 8-inch walls. When built of concrete cast in place, foundation walls shall be at

least 8 inches in thickness. When built of rubble stone, they shall be at least 16 inches thick. Rough or random rubble without bond-
8 MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS

ing or level bed shall not be used as foundations for walls exceeding 35 feet in height. (See Appendix, pars. 7 to 10, inclusive.)

3. Foundation walls for frame construction shall extend at least : 8 inches above the adjoining ground surface. (See Appendix, par.

38.) Sec. 2-3. Basement Columns.

Basement columns supporting the first floor or jiarts thereof shall

meet the following requirements:

Wood columns shall rest on metal or masonry footings extending

at least 3 inches above the basement or cellar floor. Wrought-iron, cast-iron, or steel pipe columns shall have metal'

top and bottom bearing plates. Sec. 2-4. Ventilation.

Cross ventilation shall be provided for the space inclosed by foundation walls, whether it be excavated or not. (See Appendix, par. 10.) Note.—For information on rat proofing, see Appendix, paragraph 39. SECTION 3. DWELLINGS HAVING SOLID BRICK WALLS

(These requirements apply to small dwellings and may not apply to larger

buildings or other types of buildings.)

Section 3-1. Quality of Brick and Mortar.

Brick, whether of clay or other materials, shall have an average

compressive strength tested flat of at least 1,500 pounds per square

inch, provided that no brick having a strength of less than 2,500

liounds per square inch shall be used where exposed to the weather.

(See Appendix, par. 12.)

Portland cement, natural cement, and lime used as cementing

materials in mortars shall comply with the standard specifications

of the American Society for Testing Materials with A. S. T. M.

designations as follows

:

Standard Specifications for Portland Cement C9-.30 Standard Specifications for Natural Cement ClO-09

Standard Specification for Quicklime for Structural Purposes C5-26

Standard Specifications for Hydrated Lime for Structural Purposes C6-24

(See Appendix, par. 3.) Mortar for foundation or exterior walls, chimneys, or piers shall

contain at least 1 part of Portland cement or a mixture of Portland

cement and lime to 3 parts of sand by loose damp volume, but shall

not be leaner in cement than 1 part cement, 1 part lime to 6 parts

of sand. (See Appendix, par. 13.) Sec. 3-2. Thickness, Height, and Bonding of Exterior Walls.

1. The minimum thickness of exterior solid brick walls shall be

8 inches for a height not exceeding 35 feet. If walls of greater

height are used, the thickness shall be at least 12 inches for the

uppermost 35 feet and shall be increased 4 inches for each successive

35 feet or fraction thereof measured downward from the top of the

wall. In brick walls, at least every sixth course shall be a header
MINIMUM SIMAT.U DWELLING CONSTRUCTION REQUIREMENTS 9

1 course or there shall be at least one full header in every 72' square

I inches of wall surface. Walls shall be securely anchored or bonded

1 at points where they intersect. Sawed stone shall be permitted for

•

' walls under the same circumstances and subject to the same restric- tions as solid brick. (See Appendix, pars. 14 to 18, inclusive. EeI quirements governing construction of interior walls' and partitions,

sec. 9-4. Requirements for foundation walls, sec. 2-2.)

I

; 2. Changes in the thickness of masonry walls shall be made only at the floor line.

I Sec. 3-3. Piers.

The unsupported height of isolated masonry piers shall not exceed

.1 ten times their least dimension. Stone posts that spall under fire shall not be used as supports for girders or walls in cellars or base- ments. (See Appendix, par. 11.) Sec. 3-4. Chases.

, Chases sliall not be permitted in 8-inch brick walls. In thicker

walls the liacks of chases shall be not less than 8 inches thick. Sec. 3-5. Arches and Lintels.

1. The masonry above openings shall be supported by well-but- tressed arches, or lintels either of metal or masonry, plain or reinforced, which shall bear on the wall at each end for not less than

4 inches.

2. Timber centering for brick arches may be allowed to remain,

jirovided the opening is not over 4 feet wide and that the timber

at each end bears on the wall for a distance not exceeding 2 inches. Sec. 3-6. Wood Inserts in Masonry Walls.

No timber except lintels, as prescribed in section 3-5, 2, and no

nailing blocks longer than 8 inches horizontally or nearer together

than 2 feet, shall be built into any masonry walls. (Furring. See

Appendix, par. 45, for material on advisability of furring masonry

structures. For framing details, see sec. 7.) SECTION 4. DWELLINGS HAVING WALLS OF HOLLOW

MASONRY UNITS, OR HOLLOW WALLS OF BRICK

(These requirements apply to small dwellings and may not apply to larger

' buildings or other types of buildings.)

Section 4-1. Quality of Materials.

Brick for use in hollow Avails shall be of quality at least equal

to that for use in solid walls as specified in section 3-1. The average compressive strength of structural clay tile laid with

the cells A^ertical shall be at least 1,400 pounds per square inch of

gross sectional area when tested with the cells parallel to the direction of the applied force. The average compressive strength of structural clay tile with the

cells horizontal, and Avhich are tested with the cells in that position,

shall be at least 700 pounds per square inch of gross sectional area. (See Appendix, par. 19.)

12aS81°—32 2
10 MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS

The shells of concrete block or concrete tile shall be at least threefourths inch thick. The average compressive strength of concrete block or tile used in exterior or party walls or piers shall be at

least 700 pounds per square inch of gross sectional area when tested

in the position as used in the wall, except that for use with cells vertical, units having shells less than 1% inches in thickness shall

have an average compressive strength of at least 1,000 pounds jier

square inch of gross sectional area. Concrete block or concrete tile units which will be exposed to the weather or soil in the finished

building shall not absorb more than 15 pounds of water per cubic

foot of net volume. This requirement for absorption shall be

waived when the units will not be exposed to soil or weather or will

be protected by a facing of 3 inches or more of stone, terra cotta,

brick, or other veneer. (See Appendix, par. 19.)

Mortar for walls of hollow unit construction or hollow walls of

brick shall be at least equal to that required for solid wall construction as given in section 3-1. Sec. 4-2. Thickness, Height, and Bonding of Exterior Walls.

Walls of hollow masonry units or hollow walls of brick shall not

exceed 50 feet in height above the top of foundation Avails. (See

Appendix, par. 1.) The minimum thickness of exterior Avails built of holloAv masonry

units or hollow walls of brick shall be 8 inches for a height not

exceeding 35 feet. If Avails of greater height are used, the thickness

shall be at least 12 inches for the uppermost 35 feet of their height

and at least 16 inches for the remaining loAver portion. (See Appendix, pars. 20 and 21.)

Where tAvo or more hollow units are used to make up the thickness

of a Avail, the inner and outer courses shall be bonded at vertical

intervals not exceeding three courses by lapping at least one cell completely over a cell of the unit beloAv. Walls shall be securely

anchored or bonded at points Avhere they intersect.

Veneering for Avails of holloAV masonry units shall be tied into the

backing either by a header for every 300 square inches of Avail sur- face or by substantial, noncorrodible metal Avail ties spaced not

farther apart than 1 foot vertically and 2 feet horizontally.

Facing for Avails of holloAv masonry units shall be bonded into the

backing Avith at least one header course in every six courses, or there

shall be at least one full-length header in eA^ery 72 square inches of

wall surface.

(See Appendix, par. 22. Requirements for foundation Avails, sec. 2-2. Recpiirements for change in thickness of masonry Avails, sec. 3-2, 2. Requirements covering construction of interior Avails and

partitions, sec. 9-4.) Sec. 4-3. Piers.

The unsupported height of piers built of holloAV masonry units

shall not exceed eight times their least dimension.

Sec. 4-4. Bearing for Concentrated Loads.

Walls of holloAv masonry units or holloAV Avails of brick on Avhich

beams, joists, or concentrated loads rest shall be provided Avith bear-
MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS 11

plates or courses of solid tile, brick, or concrete. Such plates or courses when of tile or concrete shall be adapted to the service

required.

Sec. 4-5. Chases.

Chases shall not be permitted in 8-inch walls. In thicker walls

chases shall not be cut but may be built in, and the back of the

chase shall be not less than 8 inches thick. Sec. 4-6. Arches and Lintels.

The masonry above openings for walls built of hollow masonry

units or hollow walls of brick shall be as required for solid wall

construction given in section 3-5. Sec. 4-7. Wood Inserts. Wood inserts in walls of hollow masonry units or hollow walls

of brick shall be as required for solid wall construction given in section 3-G.

SECTION 5. CONCRETE DWELLINGS OF MONOLITHIC,

UNIT, OR STRUCTURAL FRAME TYPE

(These requirements apply to small dwellings and may not apply to larger

buildings or other types of buildings.)

Section 5-1. Quality of Materials.

Concrete for bearing walls and piers of plain concrete shall be not

leaner in cement than a mixture of 1 part of cement, 2 parts of

sand, and 4 parts of coarse aggregate, proportioned by volume, provided that any concrete having an ultimate strength of 2,000 pounds

per square inch at 28 days may be used.

Cement for plain concrete shall comply with the standard specifications for Portland cement, A. S. T. M. designation C-9-30, of the

American Society for Testing Materials. (See Appendix, par. 3.)

Concrete aggregates shall be well graded from fine to coarse and

shall consist of natural sands and gravels, crushed rock, slag, burned

shale or clay, or other approved inert materials having clean, uncoated grains of strong and durable minerals. They shall be free

from harmful amounts of shale, clay, silt, crusher dust, soft fragments, and other deleterious materials.

Coarse aggregate shall have at least 95 per cent retained on a

h/4-inch sieve. The maximum size shall not be larger than one-fifth

the least distance between forms nor larger than three-quarters the

minimum clear distance between reinforcing bars or between reinforcing bars and forms.

Fine aggregate shall all pass a %-inch sieve, at least 85 per cent

shall pass a i/4-inch sieve, at least 10 per cent shall pass a No. 50

sieve, and not more than 5 per cent shall pass a 100-mesh sieve. (See

Appendix, par. 23.) ^ Water used in mixing concrete shall be clean and tree irom

injurious amounts of oil, acid, alkali, organic matter, or other harmful substances.
12 MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS

Sec. 5-2. Thickness, Height, and Bonding of Exterior Walls.

1. The minimum thickness of exterior concrete walls shall be 8 inches for a height not exceeding 35 feet. If walls of greater height

are used, the thickness shall be at least 10 inches for the uppermost

35 feet of their height and shall be increased 3 inches for each suc- cessive 35 feet or fraction thereof measured downward from the top

of the wall.

2. Reinforcement, symmetrically disposed in the thickness of the

wall, shall be placed not less than 1 inch above openings and extending not less than 9 inches each side of such opening, consisting of

two %-inch round rods for openings up to 4-foot spans, and two

%-inch round rods for openings up to 8-foot spans, or their respective equivalents. For openings of greater span, reinforced concrete or rolled steel beams, designed in accordance with standard methods,

shall be used.

At the corners of all openings two %-inch round rods or their

equivalent, symmetrically disposed in the wall, shall be placed at an

angle of 45° with the horizontal, extending at least 12 inches each

way from the corner of the opening.

At wall junctions or returns two %-inch round rods or their

equivalent, bent to the angle of the junction, not less than 12 inches

long each side of the bend, shall be spaced not over 20 inches apart

in the height of the wall, symmetrically disposed with at least 1 inch of concrete covering the steel.

3. Hollow monolithic Avails shall luiA^e not less than 6 inches aggregate thickness of material. Wall openings and corners shall be

reinforced in the same manner as solid monolithic Avails. The

inner and outer parts of such Avails shall be securely braced and tied

together Avith noncorrodible ties or other means to bring them into

common action. Where floor and roof systems are carried by such

Avails, proAusion shall be made for the distribution of these loads to

all parts of the wall. (See Appendix, pars. 24 and 25. Foundation

Avail requirements, sec. 2-2. Requirements for change in thickness

of masonry Avails, sec. 3-2, 2.) Sec. 5-3. Piers.

The unsupported height of piers of plain concrete shall not

exceed ten times their least dimension.

Sec. 5-4. Chases.

Chases shall not be permitted in 8-inch Avails. In thicker Avails the backs of chases shall be not less than 8 inches thick. In holloAV

monolithic Avails the chases shall not be cut but may be built in, and

the back of the chase shall be not less than 8 inches thick. Sec. 5-5. Arches and Lintels.

The masonry above openings for solid or monolithic concrete walls

shall be as required in sec. 3-5. Sec. 5-6. Unit Construction.

Precast concrete units for construction of dwellings shall be of

sufficient strength, and where necessary shall be reinforced to carry

safely the loads imposed. Connections between the several parts
: ^IINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS 13

of such structures shall be sufficiently strong and rigid to resist the

vertical and horizontal forces which may be imposed. (See Appendix, par. 26.) Sec. 5-7. Concrete Structural Frame with Inclosing Walls.

D^yellings constructed with monolithic reinforced-concrete frames

cast in metal lath or other forms, and with inclosing walls of concrete plastered or shot on metal lath, or of precast units carried by

such frames, or having reinforced-concrete bearing walls, shall be

designed in accordance with standard methods of reinforced-concrete design to carry safely the dead weight of the structure and

the live loads which may be imposed. Inclosure or panel walls

shall be of sufficient strength and rigidity to resist lateral forces and

transmit them to the framework. (See Appendix, par. 27.) Sec. 5-8. Concrete Floors, Floor Beams, and Columns.

Concrete floors, floor beams, and columns shall be designed in ac- cordance with standard methods to carry safely the loads imposed.

(See requirements governing framing in masonry walled buildings,

sec. 7.) SECTION 6. WOOD FRAME CONSTRUCTION

(These requirements apply to small dwellings and may not apply to larger

buildings or other types of buildings.)

Section 6-1. Exterior Walls.

1. Where exterior walls or parts thereof more than one story high

ai'e sheathed, the sheathing boards shall be nailed to each stud with

not less than two 8-penny nails. AVhere the sheathing is omitted

or is not laid diagonally, all corners shall be diagonally braced and

such other measures taken to secure rigidity as may be necessary.

2. Walls shall be constructed to develop a strength and rigidity

equal to that of wood studding not less than 2 by 4 inches, spaced

not to exceed 16 inches on centers and provided with sheathing or bracing as given in the paragraph immediately preceding. Wood

sheathing may be omitted when other types of construction are used

that have been proved of adequate strength and stability in tests conducted by recognized authorities. (See Appendix, pars. 30 and

35.)

3. Ledger or ribbon boards used to support joists shall be not

' less than 1 by 4 inches, shall be cut into the studs, and securely

nailed with not less than two 10-penny nails to each stud. (See

Appendix, par. 30.) Sec. 6-2. Masonry Veneer on Wood Frame Construction.

1. Masonry veneer applied to the walls of frame structures shall

rest directly upon the masonry foundation of the structure and shall

be not less than inches in thickness.

2. Noncorrodible flashing shall be installed where necessary to prevent moisture from penetrating behind the walls.

3. The masonry veneer shall be securely attached to the frame

structure at intervals of not more than 16 inches vertically and 24

inches horizontally with noncorrodible nails or ties.
14 MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS

4. A waterproof sheathing shall be securely attached to the framework of the structure back of the masonry veneer. (See Appendix,

par. 28.) Sec. 6-3. Stucco on Frame Construction.

1. Cement and lime for stucco shall conform to the requirements

for these materials as given in section 3-1.

2. Noncorrodible flashing or other expedients which will prevent

penetration of moisture behind the stucco shall be used where

necessary.

3. Back plastering shall be required where sheathing is omitted.

(See Appendix, par. 29.)

4. Where wood sheathing is used it shall be of not less than 6-inch

boards securely nailed to the studding with at least two 8-penny

nails to each stud.

5. Metal reinforcement shall be of expanded metal or wire fabric

weighing not less than 1.8 pounds per square yard and having openings not less than three-fourths inch nor more than 2 inches in greatest dimension. Where sheathing is omitted, the weight of such metal

reinforcement or mesh shall be not less than 3.4 pounds per square

yard.

Note.—For information on insulation, see Appendix, paragraph 46.

6. If a wall is back plastered, the plaster shall be of sufficient thickness to extend back between the studs a distance not less than

one-fourth inch. (See Appendix, par. 29.)

7. Metal reinforcement for stucco of any type shall be furred away

from sheathing or building paper at least three-eighths of an inch

at all points by the use of sj)ecial furring nails or devices or by

suitable metal strips unless self-furring metal lath is used.

8. The thickness of stucco when applied on metal lath or similar reinforcement shall be at least 1 inch and the metal reinforcement shall be covered at least five-eighths of an inch.

Note.—For information on plastering, see Appendix, paragraphs 40 to 44, inclusive. SECTION 7. WOOD FRAMING

(These requirements apply to small dwellings and may not apply to larger

buildings or other types of buildings.)

Section 7-1. General Requirements.

Members shall be so framed, anchored, tied, and braced as to develop the maximum strength and rigidity consistent with the

])urpose for Avhich they are used.

Sec. 7-2. Strength of Members.

1. AYood structural members shall be of sufficient size and strength

to carry the load safely without exceeding the allowable working

stress of the material. The strength of such members shall be de- termined from actual diipensions of the pieces and not from nominal

dimensions. (See Appendix, pars. 30 and 36.)

2. Stress due to dead and live loads acting singly or in combination, without wind load, shall not exceed the allowable stress specified

in Table 1. For stresses produced by wind loads or by a combination of wind loads and dead and live loads the working stresses
MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS 15

I allo\v(>(l in Table 1 may be increased by 50 per cent, provided the

i resulting: sections are not less than those required for the combined

I (lead and live loads. (See Appendix, par. 31.)

I 3. The strps in compression across the grain may be increased

j aO per cent in the case ot joists supported on a ribbon board and I spiked to the studding. (See Appendix, par. 32, bearing values for

, joists; par. 33, sizes lor girders and maximum permissible length of

I floor joists; and ]>ar. 35, for general information on use of lumber.)

Table l.—Alloirnhlc stres-.ws peniURsime for structnral Umbers in small

(IwelVniffs ^

Allowable stresses in

Species Grade 2 Bending Compression Modulus

In extreme

fiber

Horizontal shear

Parallel

to grain “short

col- umns”

Perpendicular

to grain

of elas- ticity

[Select

Lbs.lin.^ 900

Lbs.jin.^ 80

Lbs.lin.2 700 Lbsjin.i

200

1,000

Ibs./in.i

I \Common

/Select

720

750

6470

560

550 200

175

1

1, 000 \Common 600 56 440 175 1 800

niiftstTiiit (Select 950 90 800 300

}

1, 000 Cvpres.s (Common

(Select 760

1,300 72

100 640

1,100 300

300 (Common 1,040 80 880 300 1

1, 400

[Select 1,600 1,750

1,200

1, 100 880

90

1057285

68

1, 173 1,283 880

800

640

347

379

325

275 275

Douglas fir (Dense select... [Common

(Select

> 1, 600 Douglas fir (Rocky Mountain region) (Common 1 ],200

Fir, balsam (Select 900 70 700 150

}

1, 000

}

1, 200 Gum, red (Common

(Select 720

1,100

56 100 560 800

150 300 (Common 880 80 640 300 TTemlock, west cnasf. (Select 1,300 75 900 300

}

1 , 400

}

1, 100 Hemlnnk, pa.stpm (Common.

(Select 1,040

1,000 60

70 720

700 300

300 (Common 800 56 560 300 Larch, western (Select 1,200 100 1, 100 325

}

1, 300

}

1, 600 Afaple, hard (Common

(Select 960

1,500 80125 880

1,200

325 500 (Common 1, 200 100 960 500 Oak, white nr red (Select 1,400 125 1,000 600

}

1, 500

1 Pine, southern yellow . 1, 600 (Common

(Dense select.. . (Common

1, 120 1,750

100

128 800

1, 283 600

379

1,200 88 880 325

Pine, northern white, western white, and \ western yellow.

Pine. Norway J

(Select. -- 900 85 750 250

j- 1, 000

[ 1, 200 (Common

(Select 720

1, 100 68

85 600 800

250

300 (Common 880 68 640 300 . Spruce, red, white, and Sitka |(Select - 1, 100 85 800 250 1 250 j 175 1

[ 1, 200

I- 800 [Common

(Select 640

600 Spruce, Engelmann

880

750

600

1,200 960

68

70 [Common

"Select 175 J Tamarack 300 1 i 56

9576

480

1, 000 800 [ 1, 300

1 Common... 300 J

* Data furnished by the Forest Products Laboratory, Forest Service, U. S. Department of Agriculture, August, 1930.

* The select and common and dense-select grades are those specified in American Society for Testing

Materials “Standard Specifications for Structural Wood Joists, Planks, Beams, Stringers, and Posts,”

serial designation D245-27,
16 MINIMUM SMALL DWELLING CONSTEUCTION REQUIREMENTS

4. Shearing stress for joint details may, for all grades, be taken

as 50 per cent greater than the horizontal shear yalnes permitted in

the select grade.

Sec. 7-3. Sills, Joists, Girders, and Rafters.

1. Each tier of floor joists when they enter masonry walls shall i be securely anchored thereto with T-shaped steel anchors at intervals

of not more than 6 feet. Anchors shall be so attached as to release

the ends of the joists from the wall in case of fire. The ends of lapped joists resting upon girders or bearing partitions shall be securely spiked together. When abutted they shall be

connected with steel straps or dogs or by wood splices well spiked on each side. ' Joists running parallel to masonry inclosing walls shall be an-

' chored to the walls at intervals of not more than 8 feet. Such an- chors shall extend back and engage at least three joists.

Girders shall be anchored to the walls and fastened to each other

where they intersect or abut with steel straps.

When inclosing walls are of wood, each joist, beam, and girder

in the wall shall be securely spiked or anchored to the wall

construction.

Wood structures and roofs where resting on masonry foundations s or walls shall have anchors of not less than %-inch bolts. Such j anchors shall be spaced not over 6 feet apart and shall extend down * into the wall not less than 2 feet except over openings, where they ' shall be anchored in a suitable manner. (See Appendix, par. 35.)

' Wood rafters shall be spiked to the plates to develop a tie equal | to that obtained by spiking each rafter to the plate with at least three j 16-penny nails. "(See Appendix, par. 35.) | 2. Support of joists and rafters: When supported by masonry,

joists shall have bearing at least 3 inches in length.

When the ends of joists enter masonry walls, they shall be beveled

to release the joist from the wall in case of fire. Joists sui)porting nonbearing partitions which are parallel to the

joists shall be double. If nonbearing partitions cross joists near their

center, these joists shall be of size required for normal loading, with

a span 2 feet greater than the actual span. (See Appendix, par. 33.)

Rafters shall be vertically supported near the ridge when the slope

is less than 6 inches per foot, and rafters shall be thus supported

unless their feet are thoroughly tied at the plate.

3. Bridging: Floor and flat-roof joists and beams shall be rigidly

bridged at intervals not exceeding 8 feet.

4. Separation of joist ends: Wood joists shall not enter 8-inch

brick party or division walls unless recesses for timbers on both sides are provided at the time the wall is built ; otherwise a 12-inch wall

shall be required. In masonry walls the joists on opposite sides shall

be so placed as to provide at least 4 inches of solid masonry between

them.

Sec. 7-4. Bearing Partitions.

1. Bearing partitions shall be provided at the top with double

plates, each at least 2 inches thick and of same Avidth as stud. When

the studs are placed directly below each joist, a single top plate may
MINIMUM SMALL UWELLING CONSTRUCTION REQUIREMENTS 17

be used. If properly fire stopped, studs may run through the floor and rest on girders or on partition plates. (See Appendix, par. 30.)

2. Partitions not resting upon girders, or of which the studs do

not rest on partition plates below, shall have sole plates of dimensions not less than the studs.

3. Partitions unsupported by walls shall be supported on girders or double joists, or on sole plates if placed at an angle to the joists. Sec. 7-5. Nonbearing Partitions.

Nonbearing partitions shall be provided with at least one 2-inch

plate on top and bottom of same width as stud or be otherwise properly fire stopped at floor lines. (See Appendix, pars. 30 and 53.) Note.

For information on the advisability of double flooring, see Appendix,

paragraph 84. SECTION 8. METAL FRAME CONSTRUCTION

(These requirements apply to small dwellings and may not apply to larger

buildings or other types of buildings.)

Section 8-1. Construction.

Inclosure or panel walls shall be of sufficient strength and rigidity

to resist lateral forces and transmit them to the framework.

Structural members shall be designed in accordance with approved

methods to carry safely the loads imposed. (See Appendix, pars. 37 and 57.)

SECTION 9. PARTY WALLS, PARTITIONS, AND

CEILINGS

(These requirements apply to small dwellings and may not apply to larger

buildings or other types of buildings.)

Section 9-1. Party Walls.

Party walls between dwellings occupied by not more than two

families each shall be of fire-resistive construction, consisting of

wood studs covered on both sides with at least three-fourths inch

gypsum or Portland cement plaster on metal lath or any other construction having an ultimate fire resistance of at least one hour.

When constructed with wood studs, fire stops of incombustible material shall extend the full depth of the joists and at least 4 inches

above the level of each floor. Such walls shall be supported below

Abe first floor by a masonry wall not less than 8 inches in thickness.

(See also Ceilings, sec. 9-2, and Appendix, pars. 47 and 52.)

Not more than four families shall be permitted in attached dwellings Avithout a party Avail of masonry.

Where party Avails of masonry are required, they shall have the

folloAving thicknesses and shall iDe uniform in other respects to re- quirements for exterior walls of the same materials

:

Solid brick party Avails shall be of the same thickness as required

for such exterior walls given in section 3-2. Plain concrete party walls shall be of the same thickness as re- quired for such exterior walls as given in section 3-2,
18 MINIMUM SMALL DWELLING CONSTEUCTION REQUIREMENTS

Party walls built of hollow masonry units or hollow walls of brick

shall be not less than 12 inches thick throughout.

No party walls of hollow units or of hollow wall construction and

no 8-inch solid walls shall be broken into, subsequent to erection, for

the insertion of structural members.

A separation of at least 4 inches of solid masonry shall be provided

in all masonry party walls between combustible members which may

enter such walls from opposite sides. Where combustible joists, beams, and girders enter masonry walls

they shall be beveled so as to be self-releasing in case of fire. Where combustible or unprotected steel building members frame

into hollow party walls of thickness not greater than 12 inches, they

shall not project more than 4 inches into the wall and shall be so spaced that the distance between embedded ends is not less than 4

inches on all sides of the members.

Open cells in tile or blocks occurring at wall ends shall be filled solid with concrete for at least a depth of 6 inches, or closure tile set in the opposite direction shall be used.

Sec. 9-2. Ceilings.

In dwellings having apartments over one another, the floor and

ceiling construction separating such stories shall be a fire-resistive floor and ceiling consisting of wood joists, fire stopped, with a double board floor having an insulating layer between the boards and

with a ceiling of at least three-fourths inch gypsum plaster on ex- panded metal lath or any other construction having an ultimate fire resistance of at least one hour. (See Appendix, par. 52.) Sec. 9-3. Parapet Walls.

Masonry ])arty walls shall project through combustible roofs to a. height of at least 12 inches, shall have the full thickness of the top

story wall, and shall be coped. No such wall shall exceed in height

above the roof four times its thickness. (See Appendix, par. 48.) Sec. 9-4. Interior Partitions.

1. Bearing: Interior bearing walls, except party and division

walls, are considered as bearing partitions.

For bearing partitions, materials meeting the ordinary accepted

local standards for the purpose may be used.

Where not utilized as party or division walls, bearing partitions

built of solid masonry units shall be not less than 8 inches thick

and those built of hollow masonry units shall be not less in thickness

than one-eighteenth of the height between floors or floor beams.

For bearing for concentrated loads, see section 4r-4. 2. Nonbearing partitions: For nonbearing partitions, materials

meeting the ordinary accepted local standards for the purpose may

be used.

Nonbearing partitions built of solid or hollow masonry units or hollow walls built of solid units shall be built solidly against floor
l\lINBrU!\r SMAl.lv DWELLING CONSTRUCTION REQUIREMENTS 19

and ceiling construction below and above, and shall not exceed the

following unsupported lieights:

Thickness

exclusive of plaster Maximum

imsupported

height

Inches Feet

2 8

3 12 4 15

6 20

8 25 Gypsum block shall not be used for partitions where exposed con- tinuously to dampness.

SECTION 10. MISCELLANEOUS

(These requirements apply to small dwellings and may not apply to larger

buildings or other types of buildings.)

Section 10-1. Chimneys and Fireplaces.

1. Chimneys shall be built upon concrete or masonry foundations

properly proportioned to carry the load without danger of settlement

or cracking. The footing for any exterior chimney shall be below

the frost level. Chimneys in frame buildings shall not rest upon or be carried by wood floors, beams, or brackets, nor be hung or supported by metal stirrups from wood construction. (See Appendix,

par. 50.)

2. Masonry or concrete walls of buildings may form part of chimney when the chimney Avails are securely bonded into the walls of

the building and when the Hue is lined the same as an independent

chimney, hdues in party Avails shall not extend beyond the center of the Avails.

3. Corbeled chimneys shall not be supported by hollow walls or

Avails of holloAv units. Solid Avails supporting corbeled chimneys

shall be not less than 12 inches thick, and corbeling shall not project more than 1 inch per course and not more than 6 inches in any case. (See Appendix, par. 50.)

The total offset, OA^erhang, or corbel of an independent chimney

shall not exceed three-eighths the Avidth of the chimney in the direction of the offset.

. 4. Chimneys shall be built at least 3 feet above flat roofs and not

less than 2 feet aboA^e the highest point of the roof. Unless provided Avith a stone, terra-cotta, concrete, cast-iron, or other special

cap or top, the chimney lining shall project not less than 4 inches.

No chimney top shall decrease the required flue area.

5. Chimneys built of brick, stone, or other masonry units shall be lined throughout with fire-clay flue lining, provided that in chimneys having solid brick walls 8 inches or more thick the flue lining

may be omitted. Flue linings shall be at least five-eighths of an

inch thick, and shall be suitable for the purpose and adapted to Avithstand high temperatures and the resultant gases from burning

fuel. The flue sections shall be set in mortar of quality at least as
20 MTRTMUM SMATX DWELLTN^G CONSTETTCTION EEQUIEEMENTS

rich in cement as that required for walls. The joints shall be smooth

on the inside.

When two or more flues are contained in the same chimney withes

of brick or mortar not less than 3% inches thick shall be provided

at intervals not exceeding 30 inches horizontally. Where flue linings are not separated by withes, the joints shall be staggered and the,

vertical distance between joints in adjoining flue linings shall be not

less than 7 inches.

The masonry shall be built around each section of lining as it is placed, and all spaces between masonry and linings shall be filled with mortar. Linings shall start at least 8 inches below the center

line of smoke-pipe intakes or, in the case of fireplaces, from the apex

of the smoke chamber and shall be continuous the entire height of

the flue. No smoke-pipe intake shall be cut into a flue lining already

set in place. Flues shall be built as nearly vertical as possible, but

in no case at an angle greater than 45° from the vertical. Where

flues change direction, the abutting linings at the angle joints shall

be cut to fit closely, and at no point shall the cross-section area be

reduced.

6. Concrete for chimneys cast in place shall flow readily, be well

rodded, and shall be reinforced vertically and horizontall}^ The

walls shall be at least S% inches thick and shall be lined throughout

with fire-clay flue lining, provided that when the walls of the chimney are at least 6 inches thick, and provided further that quartz

gravel be not used as the coarse aggregate, the flue lining may be

omitted.

7. Concrete blocks used in chimney construction shall be at least 3% inches thick, and blocks inclosing more than one flue shall have

suitable reinforcement completely encircling the blocks and well embedded in them.

8. The walls of chimneys built of sawed or dressed stone in courses, properly bonded at corners and tied with metal anchors, shall be at least 3% inches thick. Chimney walls of other stone shall be at

least 8 inches thick.

9. Hollow masonry units shall not be used for the walls of an independent chimney, but may be used for chimneys built in connection

with exterior walls of buildings built of hollow units, in which case the chimney walls shall be at least 8 inches thick. The outer 8 inches

of a building wall may serve as the outside wall of the chimney, but

the remaining chimney Avails shall be constructed of two layers of

4-inch holloAv units set Avith broken joints, or the}^ may be built of

4 inches of solid masonry. In either case the outside Avails of the

chimney shall be securely bonded into the Avail of the building. No

chimney shall be corbeled from a Avail built of hollow units.

10. The inside effectiA^e area of flue linings shall be at least 70

square inches for Avarm-air furnaces, steam or hot-Avater boilers; at

least 50 square inches or at least one-tAvelfth the opening for fire- places; and at least 40 square inches for stoves, ranges, and room

heaters AAdien coal, coke, or Avood is the fuel used. (See Appendix,

]:>ar. 50.)

The construction and size of flues to be used for oil and gas fired

furnaces, boilers, and automatic Avater heaters shall be the same as required for corresponding appliances burning solid fuel. Vent
MTNnvrUM SMATJ. DWETJ.lNG CONSTRUCTION REQUIREMENTS 21

flues for nonautomatic water heaters, stoves, ranges, and other domestic gas appliances having relatively small gas consumption shall

liaye a flue area of at least 10 square inches, provided, however, that

this shall not ap|)ly to gas plates and portable gas heating appliances. Such flues, unless inclosed in solid masonry walls, shall be of

incombustible material at least three-fourths inch thick, with air- tight joints, and shall vent through and above the roof.

11. Connections between chimneys and roofs shall be made with

sheet-metal cap and base flashing arranged to allow for any lateral or vertical movement between chimney and roof.

12. No change in the interior dimensions of chimneys shall be made

within a distance of 6 inches above or below the rafters or roof

joists. 13. Flues shall be thoroughl}^ cleaned and left smooth on the inside.

14. The walls of fireplaces shall be at least 8 inches thick, and if built of stone or hollow units at least 12 inches thick. The faces of

such minimum-thickness walls exposed to fire shall be lined with

fire brick, soapstone, cast iron, or other suitable fire-resistive material.

When lined with at least 4 inches of fire brick, such lining may be

included in the required minimum thickness. When the fire-brick

lining is less than 4 inches thick, such lining shall not be included

in the required thickness.

15. Fireplaces, except when designed and used for approved gas

appliances only, shall have hearths of brick, stone, tile, or other

approved incombustible material supported on masonry arches. Such hearths shall extend at least 20 inches outside of the chimney

breast, not less than 12 inches each side of the fireplace opening

along the chimney breast. The arches shall be of brick, stone, hollow

tile, or other approved masonry at least 4 inches thick. A flat stone or a reinforced concrete slab may be used to carry the hearth instead

of an arch if it is properly su])ported and a suitable fill be provided

between it and the hearth. Hearths shall be of brick, stone, tile, or

concrete, as may be specified. The combined thickness of the hearth

and siqiporting arch or slab shall be not less than 6 inches at any

])oint. 16. No coal-burning heater shall be placed in a fireplace which does

not conform to the foregoing requirements.

Sec. 10-2. Combustible Construction Around Chimneys and Fireplaces.

1. No combustible beams, joists, or rafters shall be placed within

2 inches of the outside face of chimneys or from masonry inclosing

a flue. No combustible studding, lathing, furring, or plugging shal]

be placed against any chimney or in the joints thereof. Combustible

construction shall either be set away from the chimney or the plastering shall be directly on the masonry or on metal lath and furring

or on other incombustible lathing and furring material. Combustible furring strips placed around chimneys to support base or other trim sliall be insulated from the masonry by asbestos paper,

at least one-eighth inch thick, and metal wall plugs or approved in- combustible nail-holding devices attached to the wall surface shall

])e used for nailing
22 MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS

2. No combustible construction shall be placed within 4 inches of

the back wall of any fireplace. Combustible or unprotected header

beams supporting trimmer arches at fireplaces shall be not less than

20 inches from the face of the chimney breast.

3. No combustible mantel or other combustible construction shall

be placed within 8 inches of either side nor within 12 inches of the

top of any fireplace opening.

4. All spaces between the masonry of chimneys and combustible

joists, beams, headers, or trimmers shall be filled with loose cinders,

loose mortar refuse, gypsum block, or other incombustible material.

Sec. 10-3. Heating Appliances.

1. Not more than one smoke pipe shall be connected to a flue.

2. Smoke pipes shall enter the side of chimneys through a fire- clay or metal thimble or flue ring of masonry. Neither the intake

pipe nor the thimble shall project into the flue.

3. No smoke pipe shall pass through a ceiling, floor, or roof con- struction of combustible material.

4. Smoke pipes shall not pass through combustible partitions ; provided that smoke pipes from ordinary stoves and ranges may do so if protected by double metal ventilated thimbles 8 inches larger in

diameter than the pipe or 4 inches larger in diameter than the

pipe if the space between the pipe and the thimble is filled solidly

with mineral wool or other approved incombustible material. (See

Appendix, par. 51.)

5. The clear distance in all directions between a smoke pipe and

combustible construction, including plaster on a combustible base,

shall be not less than 12 inches; provided that this clearance may be

reduced one-half when such construction is protected b}^ cementasbestos board or asbestos millboard not less than one-fourth inch

thick or equivalent approved covering extending the full length of

the smoke pipe and not less than 12 inches beyond it on both sides, or Avhere plaster is on metal or wire lath.

G. The clear distance between Avarm-air pipes leading from the

furnace to vertical or Avail stacks and combustible construction shall

be not less than 1 inch unless such construction is covered with

asbestos paper and the paper coA^ered Avith galvanized or bright sheet

metal.

7. No Avarm-air pipe shall enter a floor, partition, or other construction of combustible material unless it is at least 6 feet distant

in a horizontal direction from the furnace or unless it is coA^ered aa ith

asbestos paper or millboard at least one-eighth inch thick or equivalent approA’ed protection. A clearance of not less than TV ii^ch shall

be maintained betAveen combustible construction and Avarm air heating stacks, floor or Avail ducts and their inlets and outlets, and they

shall be covered Avith not less than one thickness of asbestos paper

AA^eighing not less than 12 pounds per 100 square feet, or equivalent

protection.

8. StoA^es or ranges the loAver surface of Avhich is a portion of

the fire box shall be set on hearths supported by masonry trimmer

arches extending not less than G inches on all sides beyond such

appliances ; provided that Avhen such appliances have legs giving an
MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS 23

open air space of not less than 5 inches below the bottom of the

appliance they may be set on sheet metal underlaid with not less than one-quarter inch of asbestos or other equivalent approved in- combustible material; and provided further that where such appli- ances have ash boxes under the entire fire box and are set on legs

giving an open air space of not less than 5 inches below the bottom

of the appliance, they may be set on sheet metal. (See Appendix,

par. 51.)

9. No stove or range shall be placed within 24 inches from combustible construction nor within 18 inches of combustible supports

or combustible base of plastered construction; provided that when

such construction is protected by a shield of galvanized or bright

sheet metal or other equivalent approved incombustible material ex- tending from the floor to 1 foot above and 1 foot beyond the sides

of such appliances, these distances may be reduced one-half. (See

Appendix, par. 51.)

10. Domestic gas ranges shall have a distance between the burners

and a combustible floor of not less than 12 inches unless such floors are protected with asbestos board under sheet metal or other equivalent approved incombustible material. The space between the oven back or side of the cooking top shall be not less than 6 inches from

combustible material unless such material is protected as described

in the paragraph immediately preceding.

Sec. 10-4. Fire Stopping.

1. Fire stopi)ing shall be arranged to cut off all concealed draft

openings and form an effectual fire barrier between stories and

between the upper story and the roof space. (See Appendix, pars. 53 and 54.)

2. Furred walls: For all walls furred with wood the masonry

between the ends of wooden beams shall project the thickness of

the furring beyond the inner face of the wall for the full depth of

the beams, or a double course of bricks or other masonry above and

below the beams shall project beyond the face of the wall the full thickness of the furring. (See Appendix, par. 55, and fig. 29,

3 and 4.) Where floor beams are parallel to a wall furred with wood, there

shall be a space of not less than 2^ inches between such wall and

the nearest beam. This space shall be filled solidly with masonry

or incombustible material the full depth of the floor beams.

3. Walls studded off : Where walls are studded off, the space

-between the inside face of the wall and the studding directly over such space shall be fire stopped with incombustible material for a depth of at least 4 inches, supported by metal lath and plaster or

other suitable means.

4. Partitions : Where stud partitions rest directly over each other

and cross Avood floor beams at any angle, and the studs run down

between the floor beams and rest on the top plate of the pa^rtition

below, the spaces between the studding shall be filled in solid for a depth of at least 4 inches above each floor level with incombustible

materials.

5. Exterior Avails: Exterior walls shall be properly fire stopped

at each floor leA^el and at the level where the roof rafters connect

with the wall plate. (See Appendix, par. 53.)
24 MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS

6. Cornices: Cornices built of wood or having wood frames on rows of buildings shall be either fully fire stopped between each

building or shall be completely separated.

7. Stairs: The space between stair carriages shall be fire stopped

by a header beam at top and bottom. Where a stair run is not all in one room or where a closet is located beneath the stairs, the stair

carriages shall have an intermediate fire stop, so located as to cut off communication between portions of the stairs in different rooms, or between the closet and the room in which it is placed. Such stops

shall be made of plank or other suitable material.

If a flight of stairs leading to the second story is over a flight of

stairs leading to the basement, the underside of the stairs to the

second story shall be covered with expanded metal lath plastered

with gypsum or Portland-cement mortar, or with %-inch gypsum

lath plastered with unsanded gypsum plaster at least one-half inch

thick.

8. Warm-air pipes and registers: Where a furnace warm-air pipe

passes through a floor, the space between the pipe and floor construction shall be filled with incombustible material supported by sheet

metal or metal lath. The space between a register box set in a floor and the casing protecting the floor construction shall be filled with incombustible material. This shall include the space around that portion of the warmair pipe attached to the register box down to the bottom of the joists

in wood floor construction, and a layer of sheet metal or metal lath

shall surround the pipe and be securely nailed to the underside of

the joists to supjiort the fire stopping. When a register box is fire stopped in this manner, the space between the box and the casing may

be reduced to 2 inches; otherwise it shall be 4 inches. (See Appendix, par. 55. See also fig. 33, 1 and 2, for details.)

9. No fire stopping shall be concealed from view until opportunity

has been given the owner or his representative to inspect same.

Sec. 10-5. Private Garages Combined with Dwellings.

When a garage is located beneath or attached to a dwelling, the

following regulations as to its construction shall be observed

1. The floor and ceiling construction aboA’e the garage when it is located beneath the building, or the roof of the garage when it is attached to the building, shall be unpierced and shall be of fire- resistive construction, consisting of wood joists, fire stopped, with

a double board floor having an insulating layer between the boards

and with a ceiling of at least %-inch gypsum plaster on expanded

metal lath or any other construction having an ultimate fire resistance

of at least one hour.

2. Walls and partitions between the garage and dAvelling shall be a

fire-resistive wall or partition consisting of wood studs covered on

both sides with at least three-fourths inch gypsum or Portlandcement plaster on metal lath or any other construction having an

ultimate fire resistance of at least one hour.

3. Openings from a dwelling into a garage shall be restricted to a

single doorway; such opening shall be protected by an approved
INIINIMUM SMALT. DWELLING CONSTRUCTION REQUIREMENTS 25

swin^in^, self-closing fire door with approved fire- resistive frame

and hardware. No glass shall be permitted in such door. The doorsill shall be raised at least 1 foot above the garage floor level. (See

Appendix, par. 56.)

4. Garage floors shall be made of concrete or equally fire-resistive and impervious material.

XoTE.—For information on plumbing and electrical requirements, see Apl^endix, paragraphs 58 and 59. 126381°—32 3

c
PART 3.—APPENDIX

Purpose.

The appendix consists of explanatory matter referring to part 2

and includes information submitted through various national organizations and other sources. It is a vital part of this report. The committee has been singularly fortunate in its facilities for obtaining

data and test records from all parts of the country. It has had for

consideration a large accumulation of reliable material on Avhich

many of its recommendations have been based, thus adding greatly

to their significance. The appendix is the merest digest of this

wealth of material and is submitted for its educational value.

The Building Code Committee is convinced that the requirements

of a building code should be as brief and simple as possible. It should contain merely the minimum requirements necessary and not

be a set of specifications covering methods of building. The committee further believes that every such document should be accom- panied by an appendix, which should not be a law or ordinance, but

which should contain such general explanatory statements of the

requirements in the code as would make them easily understandable

and such other information of value as could not be obtained else- Avhere in concise form, if at all, for the education of the home builder.

The committee strongly recommends that in the event of any State

or municipality using part 2 as the basis of a building ordinance for

dwellings such an appendix be published accompanying the ordi- nance for the direct benefit of builders.

It should be further stated that the committee, after prolonged

study of the A^oluminous data at its disposal, has placed the requirements in part 2 as low as it considers safe for durable and proper

building, as indicated in part 1 of this report. The appendix contains many suggestions for better methods of building, so that they

Avill be aA^ailable for those who are financially able to take advantage

of such opportunities.

Paragraph 1. Heights and Areas.

The requirements for heights given in section 1-3, part 2, are those

recommended in the committee’s report entitled “ Kecommended Minimum Requirements for Fire Resistance in Buildings.”

In order further to simplify the requirements for wall heights,

the permissible height of all types of 8-inch walls has been set at 35 feet. For small dAA^elling construction this height is considered

safe in so far as affected by considerations of loading. Other factors, such as fire resistance, climatic conditions, earthquakes, or high

wind pressures, may make it desirable to use thicker walls for this

height. (See par. 16 of this appendix.)

In the ordinary case the 35-foot height allowed for any Avail is measured from the top of the wall to the top of the foundation. In

26
TUTNnnilVr RMAU. DWELTJNO CONSTRUCTION REQUIREMENTS 27

the case where walls do not extend more than 5 feet below the ground

level and certain types of foundation walls are therefore permitted

to be 8 inches thick, or in the case of solid concrete foundation walls which may also have an 8-inch thickness, the foundation wall must be

included in the allowable height; that is, the foundation wall must

be increased in thickness according to the requirements in sections

'^2, 4r-2, and o-2, part 2, if the total height of foundation and exterior

wall exceeds a height of 35 feet. The requirements for area in the committee’s report on fire resist- ance state that frame dwellings may be permitted to have an area not exceeding 4,000 sipiare feet. Inasmuch as the area of the averao-e small dwelling falls below this figures, no limitations on area for

this class of structure have been proposed. Attention is called to the definition of a dwelling in section 1-1, part 2. Par. 2. Weights of Materials.

For the purpose of estimating dead loads, in the absence of more

definite information, the approximate average weights of some of the more common construction materials may be taken as follows

Brickwork, solid Concrete, stone

Concrete, solid cinder

Structural tile, wall bearing

Structural tile, partition

Hollow concrete block, cinder Hollow concrete block, stone

Blaster, mortar

Granite, bluestone, and marble

Limestone

Sandstone

Bine, longb'af

Bine, sbortleaf

Bine, northern white

Douglas fir Bedwood

Spruce, red, white, or Sitka Hemlock

Cyi)ress

Oak

Cedar, Port Orford

Cedar, western, northern white

, "Weight of partition tile (unplastered):

Solid gypsum block 2-inch

Solid gypsum block 3-inch Hollow gypsum block

8-inch

4- inch

5-inch

6-inch Structural clay tile

3-inch

4-inch

6-inch 8-inch 10-inch 12-inch

Pounds per

cubic foot 120

150 no

60

546080

96

170

160 14541

38

253430

28 2932

48

29

Pounds per square foot

10

1315.5

16.5

1516

2230 rrrrrirrrrrrrrrrrrrirrrrrirzir 40

c
28 MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS

Par. 3. Quality of Materials.

Standard specifications for the quality of a number of structural

materials have been adopted by the American Society for Testing

Materials. These specifications are the result of long and thorough

investigation and represent the agreement of producers, consumers,

and general interests as to the standards of quality necessary for

practical, successful results. They are intended for incorporation in

working agreements of all sorts and under any conditions, and are, therefore, especially to be recommended for the general purposes of

building code. Copies of the specifications may be obtained from

the offices of the American Society for Testing Materials, 1315 Spruce

Street, Philadelphia, Pa. Following is a partial list of commonly

used building materials for which standard specifications have been

adopted

:

Serial No. of Material specification Portland cement C9-30

Natural cement C1(M)9

Quicklime for structural purposes C5-26

Hydrated lime for structural purposes C6-31

Gypsum plaster C28-30

Gypsum plastering sand C35-30

Gypsum plaster board C3T-30

Gypsum wall board C36-25

Gypsum partition tile or block C52-27

Keene’s cement C61-30

Building brick (made from clay or sliale) C62--30 Sand-lime building brick C73-30

Structural-clay load-bearing wall tile C34-31

Structural-clay fireproofing partition and furring tile C56-31

Structural-clay floor tile G57-31

Clay sewer pipe 013-24

(’enient-concrete sewei* pipe C14—24

Draintile C4-24

Structural steel for buildings AtU29

Billet steel concrete reinforcing bars AI5-30

Rail steel concrete reinforcing l)ars AlG-14

Cold-drawn steel wire for concrete reinforcement A82-27

Cast-iron soil pipe and fittings A74-29

Structural wood .1oist and planks, beams and stringers, i)osts and

timbers D245-30

Standard definitions of terms relating to timber D9-30

Tentative specifications, representing the best information and

experience obtainable to date, have been prepared for the following

additional materials

:

Serial No. of Material specification Concrete building brick C55-28T

Concrete aggregates C33-31T

Fire tests of building construction and materials C19^26T

Sand for use in lime plaster CG6-27T

Reinforced concrete pipe C75-30T

Gypsum wall board C36-31T

Gypsum lath C37-31T

Gypsum slieatbing board C79^31T

High early strength Portland cement C74-30T

Load-bearing concrete masonry units C90-31T

The Bureau of Standards has established a procedure under which

specifications developed by nationally recognized organizations, when

properly indorsed by the affected groups, are promulgated as com-
MINIMITM SMAI.L DWELLING CONSTRUCTION REQUIREMENTS 29

mercial standards.” This service, available on request, has been

found helpful in many lines of business. Among such commercial

standards now in effect for materials entering into construction may

be cited the following

:

CS4-29. Staple porcelain (all-clay) plumbing? fixtures.

('SJI-29. Guilders’ template hardware.

(’S20-30. Staple vitreous cliiiui plumbing fixtures. CS22-30. Builders’ hardware.

US2G-30, Aromatic red-cedar closet lining.

(’S31-31. Red-cedar shingles.

Federal specifications for materials, drafted by the Federal Specifications Board, are used by the Government as a basis for making

l)urchases. Many materials available commercially meet these

standards.

As a further aid to assist all purchasers in buying commodities,

tlie Bureau of Standards has also introduced a “ certification plan.”

Under this plan there are compiled for distribution, upon request,

lists of manufacturers who have expressed their desire to supply material under contracts based upon certain selected Federal specifications and commercial standards, and their willingness to certify to the ])urchaser, uiion request, that the material thus supplied complies

with the recpiirements and tests of the specifications and is so guaranteed bv them.

Par. 4. Simplification of Dimensions.

liecommendations for simplified lists of dimensions for a large

number of materials entering into building construction have been

proposed by industries and published by the division of simplified

practice of the Bureau of Standards. These recommendations are

i.ssued only after they have been voluntarily approved by the affected

grou])s. The economies that may be expected by adhering to the

sini})lified practice recommendations are large enough to make their use of real value. Some of the simplified practice recommendations

dealing with building materials are as follows:

R16-29. Lumber.

R7. Rough and smooth face brick ; common brick. R26-30. Steel reinforcing bars. R32. (’oncrete building units. R12. Hollow building tile. R3S. Sand-lime brick. Information concerning these publications may be obtained by addressing the division of simplified practice. Bureau of Standards,

Washington, D. C. Par. 5. Floors.

The wide diversity of floor systems of various types makes it inexpedient to furnish design tables covering all the different systems,

but the following publications or handbooks are an incomplete list which may be consulted for information

:

Steel Construction, by the American Institute of Steel Construction. Standard Specifications for Steel Joists, by the Steel .Joist Institute. Open Web Steel Joists, Simplified Practice Recommendation R94-30. Combination Structural Clay Tile and Concrete Floor and Roof Construction,

by the Structural Clay Tile Association.
30 MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS

Handbook of Reinforced Concrete Building Design, reprinted by the Portland

Cement Association. Maximum Spans for Joists and Rafters, by the National Lumber Manu- | facturers’ Association. For data on wood floor construction, see paragraphs 32, 33, and

34 of this appendix.

Par. 6, Roof Loads.

The minimum roof loads specified apply only in localities where snow loads are not an important consideration. Roofs having a slope of less than 20° are always liable to accidental loading, such as groups of moving people, storage of material, etc. Hence the necessity of moderate unit loads even where snow is not to be expected. ' Where large snow loads are to be anticipated the loadings prescribed

in section 1-6, part 2, should be increased in accordance with local experience. Par. 7. Soil Pressures.

Soil pressures should be uniform throughout the foundation to al- low equal settlement and avoid cracks in walls. For example, diagonal wall cracks showing on the plaster near chimneys in dwellings

indicate an unequal settlement between wall and chimney. The lat- ter loads the soil to a greater degree than the neighboring lighter

walls. It would be well to permit such unequal settlement to come to

rest before papering the walls. Allowable soil pressures to support footings, walls, and piers upon

several classes of soils are fixed in many building codes. The values

adopted are the expression of general ])ractice and experience. In

case of important structures the designer should explore the soil. The science of predicting supporting capacity upon the basis of lab- oratory test data resulting from samples secured by pits, borings,

etc., is now under development.

In the absence of actual test data, the following table gives a general average of the supporting value in tons ])ei- sqiiai-e foot of

different soils:

Supporting value, Character of soil ton/sciuare foot Soft clay 1 Damp clay and fine sand 2 Dry, fine sand 3 Compact coarse sand 4 Coarse gravel or poorer rocks G Hard pan or hard shale 10 Par. 8. Foundation Walls.

It has been customary to require that foundation walls be made

thicker than those immediately above them. Experience has indicated that this is not necessary in all cases. A foundation wall acts both as a bearing wall and a retaining wall. As a bearing wall it has few or no openings compared to the walls above it, and its unit

compressive stresses are usually lower. As a retaining wall it owes

practically all its stability to the weight resting upon it, and except

in very thin walls the addition of 4 inches of thickness increases its resistance to side thrust very little. In extreme cases an analysis

of the forces acting on the foundation may be necessary. If it is
MINIMUM SMALL DWELLING CONSTKUCTION EEQUIEEMENTS 31

louiul that the forces produce stresses greater than those approved

tor the masonry intended for use, or where tension is caused in the

inasoni\, the thiclviiess of the foundation walls should be increased

or the walls suitably reinforced. Par. 9. Bearing for Foundation Walls.

It is of vital importance for the permanence and the stability of a dwelling that the walls and interior piers should be supported upon

Figure 1 Broad and flat footings for foundation walls and basement columns are much more effective in preventing settlement than are undersized footings with rounded or wedge-shaped

surfaces. Footings should rest on solid, well-packed material and should never be built on frozen soil. In damp soils a

4-inch tile pipe should drain the footing and discharge into a suitable outfall. Column footings should extend above the

floor to protect the column from dampness. a permanent and unyielding material. If a hard, dry sand, gravel, or clay is encountered at the level at which the walls would naturally

rest, a very moderate spread of the foundation wall, or even no

spread at all, will be sufficient to support the load. If, on the other

hand, the material at the bottom of the wall is an artificial fill or

is underlaid with mud or peat or organic matter, it is liable to settle-
32 MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS

inent no matter how much the wall footing may be spread to dis- tribute the load. It is inadvisable to attempt to support any building which is intended to be permanent on other than a stratum of

natural ground, free from organic material. If such a stratum

can not be reached by carrying the excavations for the entire wall

down to its level, other means, such as piles, either wood or concrete,

may be employed.

A line of small drainage tile with proper outfall extending around

the outside of the foundation wall to drain the footing will help to j)revent settlement and dampness of basements.

Par. 10. Provision for Air Circulation.

Where provision is not made for circulation of air within inclosed

spaces next to the ground surface, dampness accumulates and timber

decays rapidly. Openings for the admission of air help to prevent

such decay and increase the life of the structure. The total area of

such openings should be not less than 7 per cent of the ground area

inclosed. Par. 11. Piers.

Stone containing high percentages of quartz or similar siliceous

material has been found to split and spall freely when subjected to intense heat. Posts of this material are therefore prohibited for use

as supporting members in interior spaces, as their failure is liable to cause collapse of the building. Par. 12. Quality of Brick.

The following table contains the values for strength of building

bridf made from clay or shale or sand lime as given in the standard

requirements of the American Society for Testing Materials

:

Name of grade

Compressive strength on mean gross area (bricks tested flatwise) Modulus of rupture on gross area

(bricks tested flatwise)

T^Iean of 5 tests Individual min- imum

Mean of 5 tests Individual min- imum

Grade A

Lbs.lin.i 4,500 or over 3, 500 2,000

1,000

Lbs.lini

600 or over 400

300

200 Grade B 2,500 to 4,500 450 or over Grade C 1,250 to 2,500 300 or over. Note.—

T

he above classifications are based on strength and do not necessarily measure weather resistance. In recommending that all brick exposed to the weather have a compressive strength of at least 2,500 pounds in section 3-1, part 2, experience shows that it is not imposing undue hardship on any particular product, and that for the purpose of this report it presents a simple standard that can be readily understood by the average person. Although a compressive strengfh requirement of 2,600 pounds

per square inch does not guarantee a brick of good weathering qualities, it represents a fair average for brick suitable for ordinary use

in small dwellings. Visual inspection will determine in most in- stances if a brick is underburned.
MINIMUM SMAT.U DWELLING CONSTRUCTION REQUIREMENTS 33

The standard size of building brick has been established as by

8% by 8 inches, and this standard size forms the basis for the recom- mendations in part 2. Plus or minus variations of one-sixteenth of an inch in depth, one-eighth of an inch in width, and one-quarter

of an inch in length are allowed. (See also par. 4 of this appendix.)

Par. 13. Quality of Mortar.

In proportioning cement and lime for mortar it is convenient to remember that a bag of Portland cement equals about 1 cubic foot

and a bag of hydrated lime equals about 11^4 cubic feet; also that 1 cubic foot of stih' lime putty is approximately equal to a bag of dry

liyd rated lime. The proportions of sand and cement specified in

section 3-1, part 2, are based on the assumption that loose damp

sand will ordinarily be used. If sand is thoroughly dry, a slightly

smaller relative volume is advisable. Care should be exercised where

very wet sands are used to insure that the resulting mix maintains

its required relative proportions.

It is also quite important wlien a mortar as lean in cement as 1-1-6, as specified in section 3-1, part 2, is used that the mixing be

very thoroughly done in order to get uniform strength and quality.

Weakness in compi'ession and slowness of set, coupled with its tendency to disintegrate under high temperatures, make the use of

sti’aight lime mortar undesii'able in the construction of brick walls

of the minimum tliickness here permitted. Where walls of greater

thickness are used or where 8-inch walls are used for a 1-story

building and where reasonable care is taken to prevent undue loads,

the use of straight lime mortar should be made optional.

Investigations at tlie Bureau of Standards ^ on various mortars

to determine volume changes in brick masonry indicated that among

those mortars studied the samples containing only lime and sand

underwent tiie smallest volume changes subsequent to hardening.

Little difference was noted in this respect between a mortar consisting of 1 part Portland cement, 1 part lime, and 6 parts sand

by volume and a mortar of 1 part Portland cement and 3 parts sand.

IJsing the same cement, lime, and sand in different mixes of mortar,

a mix of 1 part Portland cement, 2 parts lime, and 9 parts sand by

volume gave less volume changes subsequent to hardening than either

of the two mixes mentioned above. Such a mortar has good plasticity and adheres well to the units after the masonry is in service. It

is reported to have been used to a limited extent in field practice

' wdth good results. Natural cement.—The. use of natural cement conforming to the

test s])ecifications of the American Society for Testing^ Materials,

wherever such cement is available, should not be prohibited, as ex- perience has proved that it gives satisfactory results. (For mortar requirements, see sec. 3-1, pt. 2.)

A number of special cements for mortar available commercially,

and known as ‘‘ masonry cements,” are reported to have proved

satisfactory on many construction projects. Standard specifications

for their use are under study by a committee of the American Society

1 Volume Changes in Brick Masonry. B. S. .Tour. Research, vol. 6 (RP321), p. 100.3,
34 MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS

for Testing Materials. Such cements should be permitted whenever

it is shown by tests under standard specifications that their performance is at least equal to that of other required cementing materials. Par. 14. Thickness, Height, and Bonding of Solid Brick Exterior

Walls.

1. When the first edition of this report was in preparation in 1921

the decision to recommend the use of 8-inch solid brick walls was

governed by a thorough study of several compilations of information

and opinion on the subject. Building codes then examined indicated

a rather limited number permitting such walls.

Since that time further tests conducted at the Bureau of Standards on the compressive strength ^ and fire resistance ^ of such walls have

served to strengthen the former conclusions that from these considerations the 8-inch solid brick wall, as permitted for dwellings, is amply safe.

2. Lateral stability. —While it is true that 12-inch walls by reason

of their weight and thickness offer greater resistance than do 8-inch

walls to lateral forces, such as eccentric fioor loads, thrust from

rafters, wind loads, and expansion due to temperature difference, it must also be recognized that even the heavier walls in use must be

supported against lateral forces by cross walls or by floors at intervals measured horizontally or vertically not exceeding twenty times

the wall thickness. It is believed that the stability of walls, except

as insured by support from associated construction, is not an important consideration in determining the minimum thickness, and

that the 8-inch wall is sufficiently satisfactory in this respect.

In general, it appears that the walls of small dwellings are short

enough and sufficient reinforcement is afforded when the closely

spaced partitions and floors are anchored to the walls to make additional buttresses or pilasters unnecessary. Furthermore, it is con- sidered doubtful whether such masonry reinforcements, unless of dis- pro])ortionate size and spaced not over 10 feet apart, would materially improve lateral stability of the wall.

Evidence has been received showing that 8-inch walls have suffered

severely in localities subject to high winds, and in such regions and

those liable to severe earthquake shocks walls thicker than 8 inches

are deemed advisable.

The live-load impacts and vibrations incidental to residence occu- pancy are negligible.

Reinforced brickwork, in view of investigations of its adaptability and tests of its strength, appears to offer considerable promise.

The design of brick masonry where reinforcing rods are embedded

in the mortar joints is comparable to that of reinforced concrete. Careful workmanship and high-strength mortars are said to be

essential if good results are to be obtained with this type of construction. In foundation walls and other constructions, where additional strength may be desired above what is provided by plain

brick masonry reinforced brickwork should be advantageous.

2 Compressive Strenjjth of Sand-Lime Brick Walls. B. S. Tech. Paper No. 27G. Compressive Strength of Clay Brick Walls. B. S. Jour. Research, vol. 3 (RP108), p. 507.

s B. S. Letter Circulars Nos. 113, 228, and 229. B. S. Technical News Bulletins Nos. 120 and 124.
MIXIMU.M SMALL DWELLING CONSTRUCTION REQUIREMENTS 35

3. Fire resistance.—\\\ one of the provisions of the standard fire

test, vail constnietions to be^ tested are required to have an exposed

{ii’ea of at least 100 square feet with neither dimension less than 9

feet. Several tests made at the Bureau of Standards under the standard conditions show that 8-inch solid brick walls afford a very

hio-h de^rree ()f resistance to fire. In no case did temperatures oil the unexiiosed face of a wall during the first two hours of the test reach a point endangering ignition of combustible material, even

at cracks and imperfections.

1 and 2 illustrate the release of joists correctly and incorrectly anchored, when burned

through at the center. A good method of seating joists in thin tile walls is shown

in 3. It is evident that when a wall is exposed to fire from one side

only the exposed surface will expand much more rapidly than the

unexposed side. If the fire exposure is severe, this unequal expansion of the wall faces can be sufficient to cause collapse of the wall,

^diere buildings are sufficiently far apart the collapse of a wall

is not so serious a matter, but where buildings are close together

adjoining buildings are almost sure to suffer damage by such a
36 minimum small dwelling construction requirements

collapse. Attention should be given to this reaction of masonry

Avails under fire Avith a view to providing walls thicker than 8

inches Avhere severe conditions exist. Par. 15. Conclusions on 8-Inch Walls.

A recent revieAv of the existing codes of some 150 cities in various

sections of the country reveals that more than 50 per cent are iioav permitting 8-inch solid brick Avails for 2-story dAA^llings. In aucav of the fact that such Avails are safe from a structural standpoint, that

they provide sufficient resistance to fire exposures, and that they are more economical to build than 12-inch Avails, there is reason to believe that a great many codes still penalize the home builder b}^

requiring a greater thickness. Par. 16. Advantages of 12-Inch Walls Recognized.

"Wdiile 8-inch solid brick walls for dwellings are recommended as more economical and are proAung generally satisfactory in use, nevertheless it is a recognized fact that 12-inch Avails, clue to in- creased mass, liaA^e superior stability, hence greater ability to resist high Avind pressures. I'hey are also less subject to moisture penetration and more resistant to intense cold. Some evidence has been

])resented indicating that such Avails Avithstand earthquake vibrations

better than thinner Avails. With these thoughts in mind there is an

appreciable advantage in the use of 12-inch brick Avails for dAvellings

subject to extremely high Avinds or intense cold, and, in general,

Avhere cost considerations are not imjiortant. Par. 17. Durability and Weathering of Brick Masonry.

A great deal of research has been made both in the laboratory and

in the field on the durability and AA^eathering qualities of brick, especially of clay brick. Brick are knoAvn to be affected by frost action

;

by chemical action, including the soh^ent effect of rain ; b}^ expansion

and contraction due to moisture and temperature changes; and by

the biological action of certain bacteria, such as lichens. As far as durability is concerned, frost action appears to be the only factor

seriously affecting the life of the masonry.

Numerous tests on freezing and tluiAving of indiAudual brick lead

to the conclusion that the underburned or salmon brick are subject

to disintegration which makes them unfit for use under exposed

conditions. Well-burned brick usually shoAv a high resistance to Aveathering and should be used for exterior Avails and other exposed

jdaces.

Absorption requirements for brick haA^e not been included. TnA^estigations are still under Avay to determine Avhether or not the

percentage of Avater absorption of a brick is a measure of its Aveathering resistance.

In the past there has been a rather widespread belief that moisture penetrated through the brick of brick masonry and thus caused

dampness on the inside surface of the Avail. A study of the Avater penetration into brick masonry conducted at the Bureau of Standards

has shown that Avhen the interior surfaces of brick walls have be- come wet during a rain it is likely that Avater has penetrated through

the joints rather than through the brick themselves. Openings
MlNIMU.Al SMALL DWELLING CONSTRUCTION REQUIREMENTS 37

throu«rh tlie joints are caused by poor workiiiaiisliip or by slirinkaire of the iiiortar. itli no openings through the joints there is little piobabihty ol water penetration through a solid brick wall. As a matter ot piTcaution, plastering directly on 8-inch walls should be avoided. Furring may be used to provide an air space between the wall and the plaster. ^ Par. 18. Laying of Brick.

Dunnfr warm and dry weather brick should be wet just previous

p

being hud in order that a good bond may be obtained between buck and mortar, and so that sufficient water will be left in the mortar to permit its full set. study on the durability and strength of bond between brick mid ^oftar the Bureau of Standards in Research Paper No. 290 Durability and Strength of Bond Between Mortar and Brick, has

tlie tollowing to say regarding the wetting of brick : In this connection one should realize that it is the rate rather than the amount of absorption that must be given most consideration. A rapidly absorbing brick tends to dry the wet mortar very quickly when it is first applied. hen so quickly dried, the mortar loses plasticity and does not make intimate (ontact with the entire surlace as it should. At the same time a brick when laid should not be so thoroughly saturated that it can absorb no water A little suction is necessary to form the best bond. It is difficult to draw any

definite line even for one particular make of brick; however, each manufacturer should study his material and be able to make recommendations to the user

as to the proper degree of wetting his brick. It is common practice in our northern cities to build upon frozen

brickwork for dwellings and other small structures, but if long-continued low temperatures prevail precautions against injury and over- loading must be ob.served, and special care should be taken if brickwork is subjected to alternate freezing and thawing. Brick should

be thoroughly dry when laid in cold weather, and for best results both bricks and mortar should be w^arm, so that the latter may obtain

at least a partial set before it is frozen. Par. 19. Quality of Hollow Masonry Units.

The following table contains the values for strength of structuralclay load-bearing wall tile as given in the standard requirements of

the American Society for Testing Materials:

Absorption, per cent Compressive strength based on gross area

Class Indi- vidual maxi- mum

Indi- vidual

mini- mum

End construction Side construction Mean of 5 tests Mean of 5 tests Indi- vidual mini- mum

Mean of 5 tests Indi- vidual

mini- mum

Hard 6 to 12 15 5

Lbs.lin.'i 2.000 or more

1,400 or more

1.000 or more

1,400

1,000

Lbs.lin^

1,000 or more

700 or more

700 Medium 12 to 16 19 5 500 Soft-. - 16 to 25 28 5 700 500 or more... 350

Structural clay tile are now available commercially bearing the

certification label of the Structural Clay Tile Association. Such
38 MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS

tile is guaranteed by the manufacturer to be in accordance with

the standard specifications of the American Society for Testing

Materials. The tile are also marked, indicating the purpose for

which they are intended.

The crushing strength allowable for acceptable concrete block

and tile as given in section 4-1, part 2, is justified as being within

the average demonstrated stren^h of the material, also by the fact

that the comparatively thick shells and webs of blocks afford a better distribution of stress in the mortar joints.

Where manufactured under careful control, the quality of hollow

concrete blocks and tile may be expected to be uniform. Because

of the ease with which these blocks can be produced, however, a large number of them have been made by inexperienced persons

in small plants where no regulated process of manufacture obtained. In some instances constant local inspection has been found

necessary to insure a fair quality of material. Par. 20. Exterior Masonry Walls of Hollow Units.

1. Strength. —Many investigations have been conducted in the

past few years on the strength, stabilit^q and fii'e resistance of walls

built of hollow units, including those built of structural clay tile and tile and block made from various types of concrete. In general,

the investigations show that a marked improvement has been made

in the quality of such units. It is reported that in some localities a hollow sand-lime block is giving satisfactory results. The quality of the mortar has been found to oe one of the most important factors affecting the compressive strength of walls built of

hollow masonry units, and for that reason either a mortar consisting

of 1 part Portland cement to 3 jiarts sand, proportioned by volume,

with an allowable addition of hydrated lime not to exceed 15 per

cent of the cement by volume or a mortar consisting of 1 part Portland cement, 1 part lime, and 6 parts sand, proportioned by volume,

has been recommended for use in this type of construction. A special mortar consisting of 1 part Portland cement, 1 part lime, and 4

parts sand has been advocated by some authorities as more desirable

for use with hollow masonry units than a 1-1-6 mortar. When

units of the quality required in section 3-1 and 4-1, part 2, of this

report are used and the height limits and thicknesses also recom- mended are not exceeded, the compressive strength is well within

safe limits. Lateral stability. —Because of their lighter weight, walls constructed of hollow masonry units are less stable than walls of the same thickness built of solid units, but they have shown a very

satisfactory degree of stability under test conditions. Such walls

should be supported against lateral forces by cross walls or by

floors at intervals, measured horizontally or vertically, not exceeding eighteen times the wall thickness. As with the 8-inch solid brick

wall, the 8-inch wall of hollow masonry units is not recommended

for use in regions constantly subject to high winds, or to earthquakes.

Fire resistance. —The 8-inch wall built of hollow units has been

shown to have sufficient fire resistance for any of the uses to which

it would be subjected in small dwellings. Masonry walls of any
MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS 39

type have added fire resistance when plastered on one or both sides

with at least one-half of an inch of gypsum or Portland cement

])lastei’. Par. 21. Hollow Walls of Brick.

Laboratoiy tests on hollow Avails of clay brick have indicated that

such Avails Avhen built in 8 or 12 inch thicknesses and with bonds of

lolokbak, all rolok, or all rolok in Flemish bond are adequate in

strength for the Avails of dAvellings. In these tests construction cost data on aa^iIIs of this type shoAA^ed that there was a saving in time

and materials as compared Avith solid brick walls. The comments

in paragraph 20 on Avails built of holloAv masonry units also aDulv

to holloAV Avails of brick.

’ ^

Figure 3

Details of 8-inch hollow wall of brick (all rolok), illustrating best methods of joist support. Par. 22. Laying Structural Clay Tile.

1. A running bond of 6 inches will usually be found most satis- factory in providing for openings when using the standard sizes of tile. When liollow building tile is combined with a facing of

brick or cut stone, a masoniy bond between the two materials should

be used, so that the entire thickness may act as a bearing wall.

2. So far as possible, the cross Avebs of one course should rest upon tliose of the course below, and care should be taken to insure

full mortar joints on all AATb-bearing surfaces.

3. Arch lintels may be constructed successfully of hollow tile, but

the most ])ractical form of tile lintel is made by butting a sufficient number of tile end to end, filling the cells with concrete, and insert-
MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS

HOLLOU a/y/T3
MINIMUIvr SMAT.L DWELLING CONSTRUCTION REQUIREMENTS 41

ing reinforcing rods in the lower tier of cells, thereby obtaining

the effect of a reinforced concrete beam. The coarse aggregate for

such tilling should not exceed one-half inch diameter.

4. Sills should project at least 1 inch beyond the finished surface

of stucco, and to prevent passage of moisture a window sill of solid

material should in no case extend entirely through the wall. Par. 23. Concrete.

Laboratory experiments have shown that concrete of the best

(piality in respect to strength and durability is produced with the

minimum amount of mixing water that is practicable. The practice

of using a measured quantity of water in concrete mixes is well

established, and such mixing is governed by what is referred to as a ‘‘water-cement ratio.” For the 2,000-pound concrete required in

section 5-1, part 2, approximately 7% IT. S. gallons of water is commonh’' used for each sack (94 pounds) of cement.

P^or the purpose of classification of sand and gravel according

to size for concrete mixes it is standard practice to state that given

jiercentages of the material pass or be retained on a sieve having

openings of a designated size. Sieves are classified by number or by the size of oi)enings. A i/4-inch sieve means that the openings

are one-fourth inch or that there are four meshes to the linear inchSuch a sieve is also referred to as a No. 4. In the smaller sizes the numbers alone are usually given, and a No. 100 sieve means that

there are apjiroximately 100 meshes to the linear inch. By making

use of mechanical analysis of the aggregates better concrete may be

obtained. Par. 24. Construction Methods for Concrete Houses.

Construction practice has developed the following general types:

1. Monolithic construction, in which the concrete is placed in forms

and remains in place in the structure. Monolithic construction is accomplished with various systems of forms, ranging from those for

casting a complete house in one operation to those for casting small

portions of walls in courses.

2. Unit construction, in which precast units different from ordinary concrete block or concrete tile are emploj^ed. These structural

l)arts range from the special forms of small units, which serve merely

as inclosure walls between members of a load-carrying framework,

to large slabs forming an entire side wall of the building, or even

to the members for an entire house which are precast and transported.

3. Beinforced-concrete structural frame with light inclosure and

partition walls of reinforced concrete. This type has a structural

frame of reinforced-concrete columns, beams, and girders and floor slabs cast in place, and thin inclosure walls plastered and back plastered or shot with a cement gun on wire mesh or metal lath attached

to columns and beams.

4. Blocks, brick, or tile of concrete laid into walls with mortar

joints.

City building codes do not, in general, provide for the construction

of concrete houses of all four types described. These codes usually

contain a table of wall thicknesses, but these refer only to masonry

walls composed of units laid with mortar joints. Often the units

126381 <’—32 1
42 MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS

allowed for such walls are enumerated and include brick, tile, and

concrete block. Some codes refer to brick only.

The various systems of unit construction and the systems which

utilize structural concrete frame with light inclosure walls are generally not permitted because not mentioned in city building codes.

City building departments are prone to allow onh^ just what is provided for in the code regardless of the merit of any proposed new

type of construction. Satisfactory, meritorious types of construction obviously should be covered with general requirements for

structural adequacy, and the building department should be clothed

with the power of selection and should be furnished with the neces- sary means of investigation. Par. 25. Concrete Houses with Monolithic Walls.

The vertical loads on bearing walls of buildings not more than three

stories high are comparatively small, and the stability of the completed structure as a whole should be considered in any analysis of

wall thickness requirements for dwellings.

In plain concrete walls it is customary to place a small amount

of reinforcement over openings, at the corners of openings, and at wall junctions or returns. This reinforcement usually consists of two rods of from threeeighths up to three-fourths inch in diameter, and it appears that

monolithic walls with this amount of reinforcement may be properly

classed as plain concrete. Where concrete walls contain more than

two-tenths of 1 per cent of reinforcement and the two materials act together in resisting forces they should be classed as reinforced concrete, and the thickness should be determined by the dead, live, and

wind loads and the amount of reinforcement used.

Several systems of construction have been successfully used which

produce double concrete walls. Usually these systems produce two

walls, each 4 inches thick, with an air space between. These walls

are connected together with metal ties, which contribute something

to stability; but if the area of both walls is required to carry the

loads, positive means should be provided to transmit floor reactions

to both walls. Par. 26. Concrete Houses of Unit Construction.

The strength of large precast concrete units can be computed and

verified by tests. The structural adequacy of a system employing

units of sufficient strength will depend largely on the details of the

connections, the support afforded by adjacent units, and the stability

of the structure as a whole. Systems that employ relatively small

units should be judged on the basis of the structural adequacy of the

framework canying the units. If the units themselves are reinforced-concrete structural members, they are susceptible of theoretical analysis, and a decision as to structural adequacy will tlierefore

be based on engineering design. Par. 27. Structural Concrete Frame with Light Inclosure or Panel

Walls.

The adequacy of a structural concrete frame proposed for dwelling

houses is susceptible of analysis according to principles of rein-
MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS 43

forced-concrete design, and building codes should specifically provide for the use of such a system. Inasmuch as the structural frame

carries all the loads, the inclosure walls need have only such strength

as is necessary to transmit wind loads to the structural frame. This

has been successfully accomplished by a thickness of II/2 inches of

cement mortar plastered and back plastered on metal lath which

is attached to the structural frame of the building.' The interior

portion of exterior walls is formed by plastering on metal lath to a

tliickness of seven-eighths to 1 inch. An air space is thus provided

for insulation. The total thickness of such exterior walls is governed by the width required for window and door frames, and is usually not less than 6 inches.

Instead of constructing the inclosure or curtain walls by plastering on metal lath, the cement gun or other mechanical means of

applying concrete or mortar may be used.

In view of the relatively light types of reinforcement customary

for concrete dwelling construction, it is strongly recommended that

the concrete covering over such reinforcement be of such thickness

as to ])rovide for full protection against corrosion. Metal lath or other lightweight metal reinforcing fabric should be thoroughly

galvanized or painted.

Par. 28. Masonry Veneer on Frame Construction,

Frame structures veneered with a single layer of brick or struc- tural stone attached at frequent intervals to the wood framework

or sheathing are popular in many parts of the country, and the committee has investigated these structures from various points of view

to determine what regulations are desirable for their construction.

1. So far as structural stability is concerned, well-built veneered

dwellings can be safely constructed of the same height and under

the same circumstances as those with 8-inch masonry walls. The

structural frame should be adequately braced, as described in paragraph 35, and should be so designed as to afford a minimum of

shrinkage across the grain.

2. Although additional resistance to exterior fire exposure is furnished by A^eneering with incombustible materials over wood frame,

this is not sufficient to justify any significant differentiation as to type between such construction and the ordinary wood-frame type,

in Anew of the fact that the internal resistance is about that of frame

and the building Avhen burning offers approximately the same hazard to near-by structures.

3. Anchorage betAveen veneer and wood sheathing should be fre- quent, noncorrodible, and substantial. Openings should be care- fully flashed to preA^ent entrance of water behind the facing, and the

use of a building paper between veneer and sheathing to prevent

penetration of moisture and the infiltration of air is strongly

recommended. Some types of sheathing that have been used have

a heaA^y paper backing attached to a sheet of welded wire fabric.

With this type of sheathing it is common practice to slush in mortar

between the sheathing and the veneer. Adequate fire stops should

be installed at the floor lines and at intersection of partitions with

Avails.
44 MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS

Par. 29. Stucco Construction.

1. General, —'If stucco construction is to give satisfactory service,

there are four basic factors Avhich must be given careful consideration

(a) The building must be correctly designed and constructed for

stucco, ih) the stucco must be applied to a suitable base, (c) the

stucco mortar must be correctly proportioned and mixed from materials meeting standard specifications, and (<i) the stucco must

be applied by skilled workmen familiar with the material and its application.

It is essential that penetration of moisture behind stucco surfaces

be prevented. Poorly drained stucco surfaces should be avoided;

copings, cornices, exterior trim, and the frames of all openings

should be carefully flashed or otherwise designed to carry water

away from the stucco surface.

2. Wood framing.—IVood-frame dwellings to be finished with

stucco should be erected on well-built foundations to avoid settle-
MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS 45

inont and slioiild be adeciuatel^y braced to prevent any possible

distortion of tlie frame or unsightly cracking of the stucco surface.

dests indicate that stucco cracks are less likely to occur with

horizontal sheathing than with diagonal sheathing. Diagonal bracing stri})s of 1 by 4 inch boards let in to either face of the studs,

01 * other effective bracing, should be used with such sheathing to insure stability. Where wood sheathing is omitted, bridging between

the studs in each story, as well as diagonal bracing, should be used,

and the studs should preferably not be spaced over 12 inches apart.

3. Building paper.—Substantial building paper between furring

and sheathing improves the heat and moisture excluding properties

of the wall and prevents the sheathing from extracting moisture

from the stucco during the curing period. The bottom layer of

j)a])er should overlap the baseboard, and each succeeding strip should

lap the one below at least 2 inches. Building paper may also be

used effectively between back-plastered construction and the inner

})lastered wall.

4. Reinforcement.—Metal furring and metal or wire lath should

be fabricated from galvanized sheets or should be given a galvanized

coating or painted and securely stapled to the sheathing or to the

wood frame at intervals of not more than 8 inches apart. Metal

lath should ])referably be laid horizontally, the joints being lapped

a distance of at least one mesh and securely tied or laced with wire.

Lapj)ed vertical joints should occur over supports and should be well

stapled to avoid lines of weakness. Wood lath is not recommended

for cement stucco, but is satisfactory for use with lime stucco.

5. Bach-plastered and, open construction.—In back-plastered construction the base for the stucco is attached directly to the studs. The back plastering between the studs serves fully to incase the

metal lath, thus protecting it from corrosion, and reduces the fire hazard.

Open construction is similar to back-plastered construction, except

that the three coats are placed on the outside face of the wall. In

either of these two types of applying stucco, special attention should

be given to proper bracing and adequate insulation.

6. Masonry trails.—^lasoniy walls offer an excellent base for stucco because of their inherent rigidity. Foundations for masonry walls

should insure that settlement will be avoided. The joints should not

project beyond the face of the wall, and, if the joints are raked, an

additional key will be furnished. Where the masonry serves as a base for the direct application of the stucco, it should be thoroughly

cleaned of all dirt, loose or weathered particles, paint, grease, or other

substances which would impair bond. The masonry should also have

a sufficiently rough texture so as to provide a good mechanical bond

with the scratch coat.

7. Wetting the surface.—Surfaces to be stuccoed should be moist,

but not wet enough to yield moisture to the coat applied.

8. Mixing.—Stucco should be mixed by niachine where possible,

and careful attention given to obtaining uniform proportions and

thorough mixing. . . „ 9. Proportions.—A general proportion which is widely used tor

stucco mortar consists of 1 part of Portland cement and 3 parts ot
46 MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS

sand with hydrated lime, in the proportion of 10 per cent, by weight,

of the cement used.

10. Application. —Except on monolithic concrete or on masonry

walls having very true surfaces, three coats of stucco are considered

desirable. Plastering should be carried on continously in one direction without allowing the plaster to dry at the edge. The most com- mon practice used in applying stucco at the present time favors

keeping the scratch coat moist for a period of at least 48 hours, with

an equal period of similar treatment for the brown coat, which is then

allowed to become dry before application of the finish coat. All

necessary precautions should be taken to prevent the plaster from

drying out before attaining its set. A fine spray or mist of water

has been found to be very successful in wetting stucco surfaces.

The time of application of the various stucco coats is an open

question. It was noted in tests on stucco at the Bureau of Stand- ' ards that shrinkage cracks which developed in the scratch coat later appeared in the brown coat, and finally the same cracks appeared in

the finish coat, and therefore that it is more logical to apply all three

coats one day apart, building up a fairly heavy thickness of mortar

and keeping this uniformly wet for several days, than to expect a finish coat permanently to seal cracks which have worked through

the first two coats.

11. Protection . —Stucco should be protected from sun, rain, and

freezing weather. In general, stucco work should not be attempted

when the temperature is below 40° F. unless protection can be given

the stucco for at least 48 hours.

Note.

For a complete treatment of cement stucco, reference is made to Bureau of Standards Circular No. 311 and to the recommendations contained

in the proceedings of the Ameiican Concrete Institute, volume 26. 1930. Recommendations for Portland cement stucco are also prepared and issued by the Portland Cement Association and for lime stucco by the National Lime Association, and may be obtained by writing to these associations at the addresses

given in paragraph 60 of this report. Par. 30. Sizes of Timber and Lumber.

Wherever timber or lumber is specified in part 2, the nominal size by which it is known and sold in the market is understood, provided

that the actual dimensions are not less than those of the American

lumber standards, established in Simplified Practice Bulletin E16-29,

Lumber, by the United States Department of Commerce. The actual

dimensions of seasoned and surfaced lumber are from one-eighth to one-half inch less than the nominal.

As given in the standards referred to in the preceding paragraph,

the dressed thicknesses of structural joists, rafters, plank, factory

flooring, etc., 2, 3, and 4 inches in nominal thickness are three-eighths

inch less than the nominal. Widths are three-eighths inch less than nominal for pieces of nominal width from 4 to 7 inches and

one-half inch less than nominal for widths 8 inches or more. The

standard dressed thicknesses and widths of beams, girders, stringers,

etc., 5 inches and thicker and square timbers 6 by 6 inches and thicker

are one-half inch less each way than the nominal dimensions. The

standard lengths of all lumber and timber are in multiples of 2 feet.
MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS 47

Par. 31. Removal of Overloads on Timber Construction.

The load which a wood member, such as a floor joist or a rafter,

will sustain is dependent to a considerable extent upon the length of

time the load remains on the timber. Ordinarily a timber will carry

10 per cent more load for 1 hour than it will for 10 hours. If a given load will break a timber in 40 days, a load about one-third

greater will break the same timber in one hour. It is evident, therefore, that timber will sustain considerable overload for a time, and

for this reason temporary stresses caused by wind or snow loads

may be greater without danger or failure than those due to dead

loads or long-continued live loads.
Girder

factor

and

maximum

permissible

lengths

of

floor

joists

48 MINIMUM RMALU DWELLING CONSTRUCTION REQUIREMENTS

P,o

'O w as

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MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS 49

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Table

3.

—

Maximum

'permissible

unsupported

lengths

of

rafters

measured

from

plate

to

ridge

(Based

on

30

pounds

per

square

foot

live

load

for

flat

roofs

and

20

pounds

per

square

foot

for

wind

load

acting

perpendicular

to

the

roof

for a

rise

of1

foot

per

foot.

Weight

of

roof

assumed

to

be

10

pounds

per

square

foot

roof

surface.)

50 MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS

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-g g<

’ q ®

.2S O §

cS be O q eaiJ

3,.3.-a2:S

^ a

I a g®

i.

Department

of

Agriculture,

Forest

Service,

Forest

Products

Laboratory,

Madison,

Wis.,

November

13,

1931.
I!

I iNriNiivruiM sivrALL dwelling construction requirements 51

It is, however, important to remove the load from any overloaded

I wood floor or roof within a short time, since it is not certain that

I the floor or roof Avill not fail merely because it has held the load

' for a few hours or days.

Par. 32. Bearing Values for Joists.

The reasons for allowing a greater stress in compression across the

grain Avhen the joists rest upon a ribbon or ledger board than when

the ends rest upon or in masonry are that they are more certain

of being dry and are consequently stronger; that the stress is not

at the extreme end of the joist and in case of a slight overload they

will not yield so much; and that the joists are to be spiked to the

studding, thus gaining some support through the nails. Par. 33. Explanation and Comments Relative to Table on Girder

Factor and Maximum Permissible Lengths of Floor Joists. Use of Table No, 2. —The size of girder necessary in any small

dwelling may be found as follows:

Add together the joist spans in feet meeting at the girder. Multiply this Avidth by the figure given in Table No. 2 under “ girder

factor ” and opposite the species of which the girder is to be made.

This Avill give for select-grade timbers the minimum width of the

girder, in inches, to support one floor when the distance between

siqiports of the girder is tAvelve times its height. To get the thick-

: ness of the girder for more than one floor, multiply the thickness for

I one floor by the number of floors. When the supports under the

I girder are placed closer together, the thickness of the girder can be

I |)roportionately decreased. When the distance between supports is not oA^er ten times the girder height, common-grade timbers may be

* used, excejit that the shakes and checks should conform to the re- quirements of select grade. When it is desirable to place the posts

farther apart than given by the aboA^e rule, the girder should always

be calculated by a competent engineer or architect. Joints in built-

! u}) girders sholild occur only OA^er supports. In determining from

the table the maximum permissible lengths of joists, all figures

(except the girder factors) grouped opposite any one bracket apply

to all the species in the bracketed lines. Find the species which it

I is proposed to use and the grade of material; then run horizontally

’ across to the first length as great or greater than the proposed joist

span. The head of this column will be found marked “ 16 inches.”

’ This means a spacing of 16 inches center to center, and the figures

aboA^e give the nominal and actual sizes of joists. Three columns

farther to the right, ordinarily, the required length for 24-inch

j spacing aauII be found, although occasionally it will be found that

I the same size joist is required with either 16 or 24 inch spacing.

/ Where the floor joists are to support plastering, the length of joist

' should neA^er be greater than that given in the lowest horizontal

line in each group of species, since this length is considered to be the

I maximum AAdiich can be used Avithout serious cracking of the plastering, and lengths greater than this will give floors which shake

I considerably.
52 MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS ; Par. 34. Flooring.

Wherever cost will permit, the committee recommends that all

| flooring be double, with a layer of heavy asbestos paper or incombustible floor felt, gypsum board, or other incombustible material

between the finish and rough flooring. This will make the floor warmer, decrease sound transmission, and will delay the passage

of fire through the floor. In any event, it is advisable to put some

good type of building paper between the flooring.

Desirable features of framing for stairways are illustrated above. Note that streiif?tli lost by cuttiiij' studs and

joists is regained by reinforcing the r(>niaining timbers. Par. 35. Notes Bearing on the Use of Lumber and Timber in SmallHouse Construction.

1. Desirahility of protecting luniher. —The care of lumber prior

to use for building purposes and its condition at the time of use often

determine to a large extent the value of the building or the rate at which depreciation will take place. Green or partially dry lumber,

when not properly piled, will twist and warp in drying and will

retain this twisted and warped condition after being taken from
MINIMTTM SMALL DWELLING CONSTRUCTION REQUIREMENTS 53

the pile. Green luinber, when closely piled or stored without ample

provision for the circulation of air, is very likely to become infected

with decay. This is especially true in warm, damp weather. Decay

once started in a timber will quite frequently continue after the

timber has been placed in the building, even though it be used in a

relatively dry location where a perfectly sound, dry timber would
54 MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS

The above illustration shows some common defects in balloon frame

construction, which are avoided on Figure 7. Omission of floor headers and of tire stops permits heat losses by free air circulation ; lack of corner braces impairs rigidity ; and unecjual settle- ment results from' resting partition studs on the subfloor.
MINIMUM SMALU DWELLING CONSTRUCTION REQUIREMENTS 55

never be attacked by decay. Timbers used in a building in a fairly

green condition and so inclosed as partially to cut off circulation of

the air are very likely to be attacked by decay. In this respect

sapwood is much worse than heartwood, although in the strength

of the sound material there is no difference.

When the rough lumber is delivered at a building site but little attention is generally paid to the piling or to the protection of the
56 MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS

The above illustration shows some common faults in building modern

braced-frame construction. Note that the floor headers and fire- stopping shown on Figure 9 are omitted, that the subfloor is laid per- pendicular to joists, and that interior partition studs rest upon the

subfloor instead of the partition plates below.
IMINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS 57

The ahove illustration shous details f construction, in which each story is built as a

settlement is equalized by making the Height of horizontal timoers the same in exterior walls and interior partitions. 126381°—32 5
58 MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS

lumber from rain and sunshine. It is common practice to use some

of the building material for concrete forms. This material when

removed is not infrequently thrown around in a rather promis- cuous pile. The effect on lumber of such treatment and the ensuing

wetting and drying are often quite disastrous, resulting in development of checks, shakes, warping, twisting, and cupping. Joist material, for instance, may have been in the very best condition when

received and practically fall to pieces between the rings under such

treatment.

2. Influence of shrinking^ and swelling. —The use of seasoned lumber in the framing of dwellings is important in reducing the shrinkFigure 12

Details of sill construction. age, Avhich would otherwise cause considerable trouble if green lumber was used. Shrinkage can be partly eliminated by proper design,

but both proper design and seasoned lumber are desirable in quality

construction. If green lumber is used and one end of a joist rests on the foundation and the other end on the top of a timber girder,

the girder will shrink and lower that end of the joist. It is generally good practice to place the girder flush with the top of joists,

which can be accomplished by supporting joists on members spiked

to the side of the girder.

Care should be exercised when installing either interior or exterior

trim, which ordinarily is delivered to the job in a well seasoned,

dry condition. If it is placed over wet plaster or allowed to become
MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS 59

wet from other causes, such as being stored in the open, miter joints

will first open at the outer corner, and later, when the material be- comes dry, will oj^en throughout their entire length. Some of this

difficulty may be overcome by back painting or priming of trim and

finish before it is put in place. The bad influence of shrinking and

swelling will be much greater when flat-grained material is used

than when quarter-sawed stock is used, since flat-grained material

shrinks and swells about 50 per cent more than quarter-sawed stock

with the same moisture changes. Quarter-sawed material is much

less inclined to twist and warp than flat-sawed material, and also has the advantage of offering a more uniform resistance to wear. From this it will be seen that quarter-sawed finish flooring and the

like are much superior to flat-sawed material, even when what is usually the chief factor, its appearance, is disregarded.

3. Considerations affecting joist si-zes.—In determining the size of

joists and the grade of material to be used, the following points

should be borne in mind : The stiffness of the floor is quite important if the dishes are not

to rattle and the plastering to crack. The stiffness of a joist of a given span under a given load is proportional to the cube of its height. Thus, if the height is increased by a given per cent, the

increase in stiffness is more than three times this per cent. This

is true so long as it is not so thin and high that it buckles sidewise under the load. The stiffness of a joist is but little influenced

by the grade of the material. The load which a joist of a given

length will hold without breaking varies as the square of the height.

The load which a beam or joist will sustain is dependent upon the

defects and the quality of the clear wood. It is not good economy to skimp on the height of joists, since the lower-grade material with

a greater height will probabl}^ give a more satisfactory floor at the same price than could be obtained from the higher-grade material

and correspondingly shallower joist. It is not usually good economy

to use joists over 16 feet long, since it requires additional bridging,

a greater depth of joist, and there is usually a considerable advance

in the price per board foot of the lumber.

4. Cost influenced hy length. —In the manufacture of lumber, es- pecially in the large mills that cut Douglas fir and pine, there is great advantage in having the lumber of uniform length. The most

economical length to handle appears to be 16 feet. In the stacking

of lumber it is very necessary to have it of uniform lengths, so that it can be properly held in place while drying. Even after

the lumber is dry, ends of boards projecting from the pile will usually become checked and warped and of little value.

^ On account

of these and other reasons which might be mentioned, it is common

to manufacture lumber in lengths which are multiples of 2 feet;

12, 14, and 16 feet being the ordinary standards. Shorter^ lengths

may come in on account of the limited lengths of logs which it is economical to take from the tree or as a result of cutting off defects

in trimming.

The National Committee on Wood Utilization has made a special

study of the possibilities of utilizing short-length lumber and has

pointed out that with more general use substantial economies might

be effected both for the manufacturer and consumer.
60 MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS

Lumber and timbers are produced in lengths greater than 14 or 16

feet, but such material usually commands a greater price. In the

designing of a house not infrequently the size of a room may be

changed by 6 inches without any material inconvenience and joists 2

feet shorter may result. The height of the ceiling of a room may be

changed an inch or two in order to avoid extra lengths of studding

or the plate may be double in place of single, and many other ex- pedients may be resorted to in order to utilize the full length of the

lumber as it comes from the saw, the resulting building being just as satisfactory and just as well constructed, but at a lower cost.

5. Laminated girders.—Butt joints in laminated girders, such as to reduce the effective section to less than required to support the load,

should occur over supports.

6. Importance of thorough hrojcing.—Proper bracing of a frame

building is most important. If the exterior walls are to be sheathed,

they may be braced most effectively by putting the sheathing on

diagonally and thoroughly nailing it to the studs. Such placement

of the sheathing is two to four times as effective as horizontal sheathing. Long, continuous braces let into the faces of the studs and

thoroughly nailed to them will increase the rigidity of a horizontally

sheathed wall to such an extent that it will com])are favorably with

a diagonally sheathed wall. Braces cut on a bevel and nailed in

between the studs on a line are not so effective as continuous braces.

If used at all corners, however, and made as long as the let-in braces,

they will increase the rigidity of a horizontally sheathed wall about

oO per cent. So-called “ bridge ” or “ herringbone ” bracing placed

at mid-story height does not increase the rigidity of a wall to an

extent which would justif}^ the expense of putting it in for this

purpose.

Wood lath and plaster is more rigid than many types of sheathing

or sheathing and bracing. Under normal conditions plaster may

furnish all the rigidity required for most pur])oses. However, as the

plaster begins to crack from shrinkage, settlement, or other causes, the rigidity of the sheathing comes more and more into ])lay. Thus,

in violent winds or earthquakes, it is the sheathing and bracing that

become all important in preventing complete destruction. It is logical, too, that slightly more bracing than is needed to resist or- dinary distorting influences will in the long run more than ])ay for

itself through diminishing, if not entirely eliminating, maintenance

costs that result from the structure getting out of alignment.

It is also important that the building be thoroughly tied to resist

the thrust of the rafters. When it is not feasible to tie the building

together at the foot of the rafters, the thrust may be transferred

to the end walls by a system of diagonal bracing on the underside of

the rafters. This in reality makes trusses of the two halves of the

roof which are nailed together at the peak.

In small buildings this system of bracing may be used to eliminate

very objectionable ties across the center of the building. In a garage

the end containing the doors will not get out of shape if a proper

system of bracing is used on the roof or underneath the ties and if the other three walls are well braced.

7. Anchoring of roofs and of wood huildings to foundations.—The

necessity for anchoring roofs and buildings depends upon the char-
IMTNIMUJVr SMALL DWELLING CONSTRUCTION REQUIREMENTS 61

Jicter of tlie and the severity of storms which may be

micountered.

The most common storm damage is to roofs. A roof with laro-e overhanging eaves, if not strong and well tied, is likely to be entirely torn off. The most general type of failure is for the side of the

roof away from the wind to be lifted off. The greater part of the

damage would be eliminated if the rafters were thoroughly nailed or otherwise tied to the plate and the tips of the rafters tied by

collar beams thoroughly nailed.

Frame buildings are sometimes blown over, slid on the foundation,

or picked up and carried by the wind. The following observations

of damage done by the Sejitember, 1928, Florida hurricane and the

Rockford (111.) tornado will help in determining the necessity for

anchorage. The chief damage to most of the houses was in the roof. The Florida hurricane upset and tore to pieces many houses of light

construction. Frame houses of good, fairly heavy construction (that

is, well nailed, braced, and tied and having subfloors, sheathing,

and plaster) suffered little damage even when exposed to the full force of the storm. Xone of this heavier type of construction

appeared to have been moved on the foundation.

The Rockford (111.) tornado tore down or carried away many

garages and roofs and lifted some of the heavier types of houses,

moving two entirely free of their foundations and shifting others

a few inches to 3 or 4 feet. It is very evident from these examples that roofs should be well

fastened, that the lighter buildings should be anchored, and that in

a large })art of the country it is advisable to fasten even the heavier

frame buildings to the foundations.

8. A series of tests on the rigidity and strengfh of frame walls

conducted at the United States Forest Products Laboratory, at IMadison, Wis., in cooperation with the National Lumber Manufacturers’ Association has answered many previously unsettled questions about the design of wood framing. The results of these tests as they affect the design of wood framing have been incorporated in

the requirements and information contained in this report.

Nearly 50 frame walls about 9 by 14 feet, with 2 by 4 studs spaced

16 inches on centers, were tested'; rigidity, as shown by the end

thrust necessary to cause a given movement of the end posts from

their upright position, and the strengfh, as shown by the end thrust

necessaiy to cause failure of the whole panel, were measured.

A tabulation of the test data is given in Tables 4 and 5. The

maximum loads producing failure under the assumed conditions are given in pounds. Comparisons of one type of framing or bracing

with another type can be made by referring to the number given

under the heading “ Stiffness factor ” or “ Strength factor.” The

stiffness or strength of a horizontally sheathed panel with two nails

in each board at each stud is taken as unity, and the stiffness and

strength of all other panels are then compared with this panel.

Thus a diagonally sheathed panel, two nails in each board at each

stud, no braces, and the boards in tension, is approximately 4.2 as

stiff and over eight times as strong as the horizontally sheathed unit

panel.
Table

4.

—

Results

of

tests

of

panels

without

window

and

door

openings

62 MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS

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Forest

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U.

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Over

8.
Table

5.

—

Results

of

tests

of

'panels

'with

window

and

door

openings

MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS 63

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64 MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS

Par. 36. Lumber Grade Marking.

The practice of stamping lumber with a grade-mark and a trademark in order that its actual grade and its producer may be easily

identified has been approved in the American Lumber Standards.

(See par. 30.) Although this practice has not become universal, a number of the larger producers have adopted it. Lumber thus

marked and when backed up by the guaranty of the producer assures the consumer that he is getting what he has ordered. Without such

marking the purchaser is dependent on the dealer to furnish the

grade specified, and, in the usual case, he has no way of telling if the material furnished meets the requirements for that grade.

Figure 13

1. Right method 2. Wrong method The illustrations show desirable and undesirable framing around window openings. The

double headers and window studs in 1 are as stiong and rigid as continuous studs, and

with the stiffeners at the sides help to prevent windows from binding and rattling. The calking and rabbeted strip beneath the sill excludes air, which otherwise enters

freely. Par. 37. Metal Construction.

The use of a metal frame for small dwelling construction has

been tried out in a number of cities. Such framing is, of course, easily susceptible to theoretical stress analysis, and questions as to

its structural adequacy can be based directly on engineering design.

While dwellings of this nature have not yet been developed extensively enough or have not yet been in use sufficient time to enable

detailed requirements concerning their erection to be formulated,

requirements of a general nature may be included.
MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS 65

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66 MINIMUM SMALL DWELLING CONSTKUCTION REQUIREMENTS

Metal studs for walls and partitions have been made up from

angles and assembled with separation plates that are bolted, riveted, or welded. These members are perforated with holes spaced about

2 inches on centers for ease in assembling and for attaching the lath.

Sills, girts, and plates are made

up from standard channels or

other sections and are also perforated for assembling.

Floor s3"stems for use with this

framing are usually of steel joists or beams made up of bars

welded together, expanded from

rolled sections, built up of channels or angles of less than standard weight, or rolled into struc- tural shapes of less than standard weight. Standard weight I beams and channels are also used.

Tension bridging has been found

to give good results with these

joists.

Incombustible first floors for

dwellings have been widelj" advocated to reduce the fire hazard,

and the floor s}^stems just described may be adapted to any

type of construction. To develop at least one hour fire resis- tance, the top slab and ceiling

construction should be at least equal in fire resistance to that

listed for floors in paragraph 52

of this appendix.

Other developments in metal

dwellings make use of metal

sheets which are assembled by

Avelding. Insulation is used to prevent heat transmission

through the walls. Various types

of interior and exterior finish are employed with this method of

Fiouke 13 construction.

Wood shrinks crosswise, not lengthwise of the fiber. A dwelling framed as showm

above will in time settle from 1 to 2 inches more in the center than at the

walls. This renders floors uneven, causes

plaster to crack, and makes doorr bind and rattle. Equal settlement, as obtained by the method shown across, will greatly diminish these effects.

Par. 38. Termite Protection.

The Bureau of Entomology of

the United States Department of

Agi'iculture has made investigations for a number of years con- cerning the habits of the antlike

insects known as termites. While

at one time it was thought that termites were confined mostly to tropical countries, research has shown that many sections of the United

States, particularly the Southeastern, Central, Western, Southwestern, and Pacific Coast States, are infested with them. In many
MINIM UAr SMALL DWELLING CONSTRUCTION REQUIREMENTS 67

instances the damage to wood and other material subject to attack

])V termites has been found to be serious. Much information has

therefore been disseminated by the Bureau of Entomology in order

properly to acquaint the public

with the habits of the termite and

to point out relatively simple

methods by which protection may

be secured.

For the most part, the termites

which cause the greatest struc- tural damage to building are those

which live in the ground. Such

termites are dependent upon moisture in order to live, and this

moisture is obtained from the

ground. When the insects are shut off from this supply, they

dry up and die. Obviously, where

wood members are in direct contact with the earth they are directly exposed to attack. Termites also penetrate masonry walls

where they are not constructed

witli tight joints and, by means

of shelter tubes built of earth and

])ulverized wood, they crawl up

tlie extei'ior of masonry walls ta

the underside of the material to be attacked. It has been estimated

that ample protection can be obtained at a cost of approximately

2 ]:>ei* cent of tlie first cost of a building. It should be remarked

that an initial expense of this sort may save many times the amount

in repairs and replacement at a

later date, as well as prevent possible structural failure.

As a result of its investigations on this subject the Bureau

of Entomology of the Department of Agriculture suggests the

following regulations for preventing termite attack

:

Wood or fiber products, when an

approved preservative has not been

forced into the product, shall not be

placed in the earth or within 18 inches

thereof, excepting: wood columns or

posts over a concrete floor, which columns shall be provided with noncorroding

metal or concrete base plates or footings 6 inches above the floor. This applies

to steps, which shall be laid over a concrete base, projecting at least 6 inches

Figure 16

If a building is framed to equalize the

total height of horizontal timbers in exterior walls and interior partitions, their relative positions remain the same

after settlement occurs. This helps to avoid plaster cracks and other inconveniences. (See fig. 15.)

beyond the supports of the steps. Timber to be used in contact with the earth shall be thoroughly impregnated

by a standard-pressure process with coal-tar creosote or other equivalent

preservative. Timber should be completely cut to proper dimensions before
68 MINIMUM SMALL DWELLING CONSTKUCTION REQUIREMENTS

treatment whenever possible, but when cutting after treatment is unavoidable

the cut surfaces shall be thoroughly coated with coal-tar creosote or other equivalent preservative.

Masonry foundations and footing shall be laid in Portland-cement mortar. Foundations built up of masonry units, whether hollow or solid, shall be

1. Wrong method

PLATt--

Blockihq POUBU

Meaper

on Cpqe -iRussino iPouBLt Poor 5tup

2. Right method Figure 17

Inadequate framing over wall and partition openings, illustrated in

1, permits local settlement, causes unsightly plaster cracks, and

spoils the fit of doors. The precautions shown in 2 help to prevent these undesirable results. Note that the plate, lu'ader. and

door studs have been doubled, and the header turned on edge to afford greater strength. The short diagonal and horizontal members form a truss which provides rigid support for joists over the opening.

capped below woodw’ork with at least 1 inch of Portland-cement mortar, or

the mortar and slate, or solid or joined noncorroding metal, or other equally

efficient seal. In the case of frame buildings, a metal termite shield shall be provided,

continuing completely around the top of the masonry foundation, including
MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS 69

all iiilhn-s, suiiports, and piping, below the woodwork of the building, or both the inside and outside surfaces. Such a shield may be formed of a stri of noncorroding metal (such as copper, or zinc, or an alloy composed of 28 per cent of copper, („ per cent of nickel, and 5 per cent of iron, manganese and silicon), hriiily inserted in the surface of the masonry, or between the

Figure 18

Careless cutting and notching of timbers often weakens

floors unnecessarily ; 2 by 6 inch partition studs accommodate vertical pipes readily and without undue loss of sup- porting capacity, when notched. Horizontal pipes should

be run through the centers of joists to avoid weakening them and to leave a good nailing surface for the floor. foundation and the wood, with the projecting edge bent downward at an angle

of 45° and extending horizontally at least 2 inches from the face of the foundation. In masonry buildings this shield can be inserted in the masonry

at a height at least 18 inches above the ground. Floor sleepers or joists embedded in masonry or concrete, or laid on concrete which is in contact with the earth, shall be impregnated with an approved

preservative.
70 MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS

Expansion joints between concrete floor and wall shall be fllled with liquid

asphaltum and the right-angle joint covered with a sanitary cement mortar

or Portland-cement concrete flnish of an arc of at least 2 inches in length.

The ends of wooden beams or girders entering masonry or concrete shall not be sealed in, but shall be provided with boxes affording an air space at the end of the piece of not less than 1 inch at side of member, unless the ends of such timbers are impregnated with coal-tar creosote or other approved

preservative.

Where there are spaces under floors near the earth, they shall be exca- vated so that there will be no earth within 18 inches of the wood, and they

shall be provided with cross ventilation. Such ventilating openings shall be

proportioned on the basis of 2 square feet for each 25 lineal feet of exterior wall,

except that such openings need not be placed in front of such building. Each

opening shall be provided with 20-mesh noncorroding-metal screening, including

windows in attics. Where timber is used in roofs of the flat type, the roof shall, unless protected on the weather side vdth a waterproof covering, have a slope and run-off

sufficient to provide proper drainage.

All wooden forms on foundations shall be removed from masonry work within 15 days ; grading stakes shall be removed before laying concrete floors. Par. 39. Rat Proofing.

Within the past few years considerable attention has been directed

toward making buildings resistant to infestation by rats. Aside

from the potentialities of spreading disease, rats destroy food and

cause insanitary conditions.

Obviously, the individual dwelling presents its own problem, but

there are two general principles that may well be considered in

connection with making any building resistant to rat invasion.

First, all exterior openings should be protected with tight screens, gratings, or doors; and, second, the walls, floors, or similar con- cealed spaces should not provide an uninterrupted passage for the

rats to enter. Proper fire stopping of such spaces as recommended

in section 10-4, part 2, will in a large measure prevent access to

tliese locations.

Much work has been done in combating rats and bubonic plague

by the United States Public Health Service and by the Department

of Agriculture. Information concerning more detailed requirements

of this nature can be obtained from these departments.

Par. 40. Plaster and Other Wall Coverings.

Plaster is recognized as having a number of valuable jiroperties

aside from its usual function of providing an interior flnish for

walls. When made wdth gypsum or Portland cement and applied

to metal lath it provides a very considerable degree of fire resistance.

Its weight also adds to the stability of a dwelling. When omitted,

adequate anchorage to the foundations becomes increasingly essential.In no place is the importance of good, honest construction more

evident than in the plastering of a house. If the general construction is neglected or skimped, the results are shown by the unsightly

cracking and sometimes dangerous falling of the plaster. Therefore the committee, realizing that under the best of conditions it

is impossible to avoid all cracks in plastering, wishes to emphasize

the necessity of good building. Following are some of the common

causes which result in cracked plastering: (1) Inadequate or faulty

footings under bearing posts, (2) too small girders or too few bear-
MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS 71

iiig posts, (3) joists of insufficient depth, (4) joists under partitions

not doubled, (5) improper framing over wide openings, ( 6 ) uneven

settlement due to shrinkage of wood frame improperly designed

and constructed, (7) chimney not independent of the frame, ( 8 ) settlement of wall footings and foundations, (9) separation of partitions from walls, and ( 10 ) failure to conform to good plastering

standards.

Measures by which some of the above causes of plaster cracks can be wholly or in part overcome are shown on Figures 1, 13, 15,

16, 17, 19, 24, and 26. Suitable design of footings is illustrated on

Figure 1 , proper framing over and around wide openings on Figures 13 and 17, framing to bring about uniform settlement on

Figures 15 and 16, methods of framing around chimneys and fire- places on Figures 24 and 26, and approved methods of attaching

inside partitions to walls of frame dwellings on Figure 19. When gypsum wall board is used in place of lath and plaster, it should conform to the specifications of the American Society for

Testing Materials. Gypsum lath at least one-fourth inch thick

may be used in place of wood lath. Gypsum lath three-eighths

inch thick, with the joints covered with a 3 by 3 inch or wider strip

of metal lath and plastered with at least one-half of an inch of

gypsum plaster consisting of 2 parts of gypsum and 1 part of sand

by weight, has a fire resistance of at least one hour. When gypsum

lath is used it should conform to the specifications of the American

Society for Testing Materials.

Fiber boards provide an economical wall surface. They should be

kept in a thoroughly dry condition from the time they are manufactured until applied. (See also par. 46.)

Studies of fiber boards used as wall boards and insulating boards

have been made by the Bureau of Standards.^ The following extracts are from specifications suggested by the bureau in relation to

this product.

In respect to dimensions, the boards may be secured %, 3%^, %, Ai? and tV inch thick, 32, 48, and 64 inches wide, and 6 to 16 feet long,

with all intermediate lengths in even feet. The thickness is rela- tively unimportant; and, owing to the uncontrollable variation in

the thickness of homogeneous boards, a tolerance of minus 5 per cent and plus 20 per cent in thickness is suggested. Suggested tolerance

for width and length are, respectively, plus or minus one-eighth

inch and plus or minus three-eighths inch.

Flexural hrealcing strength. —Not less than 10 pounds for the

shorter direction of the board.

Water ahsorption. —Not more than 65 per cent of the original

weight of the board.

Expansion . —Not more than 0.7 per cent in the shorter direction

of the board.

Par. 41. Preparation of Base for Plaster.

When plaster is applied directly to masonry surfaces, these should

be rough and of coarse texture but not uneven ; free from dust,

laitance, or other loose material which will prevent a good bond

< Properties of Fiber Building Boards. B. S. Miscellaneous Publication, No. 132.
72 MINIMUM SMALL DWELLING CONSTEUCTION REQUIREMENTS

between plaster and wall; and particularly from grease, which will cause discolorations. The wall surface should be wet enough so that it does not withdraw water from the plaster, but not so wet as

to fill the surface pores and prevent good bond or interfere with

hardening. Care in this respect is not so important with lime plaster as with gypsum, because lime holds water against suction better

than gypsum and because water is not required for hardening lime,

while it is for gypsum.

To prevent undue laterial expansion and contraction of wood

lath, which shears and loosens the plaster keys, such lath should not

be over by three-eighths inch in section and key spaces should

be not less than three-eighths inch for lime plaster and one-fourth

inch for gypsum plaster. Wood lath should be thoroughly wet when

plaster is applied. Lath should be attached to at least three supports, and good practice requires broken joints at least every eighth

lath. Expanded metal lath, weighing at least 2.5 pounds per square yard,

or No. 20 wire cloth having 2^^ meshes to the inch, are recommended

for a spacing of studs not exceeding 16 inches. Expanded metal

lath for ceilings applied to the underside of wood joists should be

not less than 3.0 and 3.4 pounds per square yard for joists, with a spacing of not more than 131/2 and lb inches on centers, respectively.

Greater spacings demand heavier lath or special stiffeners. Ends

of sheets should be joined over supports and horizontal edges lapped

and laced securely with wire. Continuous sheets bent around cor- ners tend to prevent cracks in the plaster. Metal lath should be

fabricated from galvanized sheets or should be galvanized or painted.

Gypsum lath consists of an incombustible core of calcined gypsum

surfaced with a fibrous material firmly bonded to the core. Gypsum

lath is usually manufactured with a width of 16 inches, lengths of

32 inches and 48 inches, and with a I/4 and % inch thickness. In some localities the lath can be obtained in a 32 by 36 inch size. For a 16-inch spacing of studs or joists, i^-inch lath may be used.

Gypsum lath should be securely nailed at each support. Nails should

be spaced not over 4 inches apart and joints so staggered that vertical joints in wall will not meet the ceiling joints. Vertical joints

should be broken. The surface of the lath is finished so that plaster

adheres readily and should not be wetted when plaster is applied. Par. 42. Plaster Materials.®

The essential ingredients of plaster are a cementitious material,

such as lime, gypsum or Portland cement, an inert aggregate of

sand and water. Hair or fiber is customarily added to act as a reinforcement while the plaster is in a plastic state, and thus keeps

it from breaking. A “ neat ” plaster contains no aggregate.

Lime, gypsum, or Portland cement may be used alone as the ce- menting material, lime may be mixed with Portland or Keene’s

cement, or Portland cement may be mixed with lime. Neither

gypsum nor Keene’s cement should be mixed with Portland cement.

Lime will carry about twice as much sand as gypsum as ordinarily

used, but the setting time of gypsum plasters can be more easily

® B. S. Circular No. 151. entitled “Wall Plaster, Its Ingredients, Preparation and Properties,” gives a detailed description of wall plasters and their properties.
IVIINIMUM SMALL DWELLING CONSTRUCTION EEQUIEEMENTS 73

regulated. Gypsum plaster has greater inherent strength than lime

})laster, and its better fire-resistive qualities are important when fire barriers are to be constructed. Lime plaster can be brought to equal

strength by tempering with Portland or Keene’s cement. Portland

cement or lime plasters are more resistant to moisture than gypsum

])lasters. Selection of plasters should be made with reference to

local practice, better work usually resulting if the workmen are familiar wdth the materials.

Keady-mixed (dry) plaster can be purchased which contains all the ingredients, gypsum or lime, sand, etc., so that all that is neces- sary is to add water to prepare the plaster for the scratch or brown

coat. Such plasters offer the advantage that they are mixed by machinery and under careful supervision, thus securing a careful selec- tion of ingredients, good proportioning, and a very thorough mixing.

Their disadvantage is the cost of transportation, which might be

offset in localities where a good sand is not available.

I In some cities a ready-mixed mortar (ready-mixed lime plaster to

I which water has Ijeen added) can be obtained, and it is equally ser-

. viceable as a mortar, stucco, or plaster. The use of such a plaster

I saves storing and mixing on the site, offers an opportunity for more

thorough aging of the lime putty, and allows the mixing to be more

thorougli than would result by hand methods. Its use is determined

by whethei' or not the delivered cost compares favorably with the

cost of preparing tlie plaster on the job.

Gyi)suni wall board represents the nearest present approach to manufacture of completed plaster at the factory, ready to be erected

in place. Gyi^siim wall board consists of an incombustible core of

^ calcined gyi)sum between two layers of tough, sized, protective fiber covering and is supplied in 32 or 48 inch widths, in lengths up to 12

I feet, and in thicknesses of one-fourth, three-eighths, and one-half

inch. It should be so erected that all ends and sides are always over

: a sup])ort. INIetal tape, or fabric, and special wall-board finisher

' should be used in finishing the joints. The walls and ceilings may be

, ])aneled or the entire surface painted or papered, as desired. Wall

board jiossesses the essential characteristics of rigidity, strength, and

finished surface common to plaster.

!' Par. 43. Mixing and Application of Plaster.

,, 1. Mliving . —^lachine mixing, due to more thorough mixing and

I

- better control of conditions, gives a more uniform and better plaster

!l than usuallv results from hand mixing. In mixing plasters other

I ; than lime, whicli requires soaking before used, the dry materials

should be mixed thoroughly to a uniform color and then added to

I the water and again thoroughly mixed to a uniform consistency.

' Directions for slaking quicklime and for screening and aging the

< jiutty are given in the appendix to the Specifications for Quicki lime of the American Society for Testing Materials, serial

j designation C5-26.

1 2. Proportions. —Proportions of sand and lime or gypsum will

> vary with each grade or make of materials. The following proporl! tions bv volume are in common use

II I For scratch coat on lath, 1 part lime to of sand, 1 of gypsum

to 2 of sand, or 1 of Portland cement to 3 of sand. In all cases,

i 126381°—32 6
74 MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS

1

Built Up Corner

Wall Stup

Post Wall Stup —

Corner Stup2 Figure 19

1 and 2 show proper methods of securing backing for lath where partitions meet outside walls at or between wall

studs. By such means firm backing is afforded for the ends of the lath and no lath extend through from room to room.
MINIIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS 75

liair or fiber niay be added in amounts not to exceed 3 bushels per

cubic yard of sand.

For scratch coat on masonry, 1 part of lime to 3 of sand, 1 of

gypsum to 3 of sand, or 1 part of Portland cement to 3 of sand. If a

finish coat is to be used, hair or fiber may be added to the scratch coat in amounts not to exceed II/2 bushels per cubic yard of sand.

For brown coat, 1 part of lime to 3 of sand, 1 of gypsum to 3 of

sand, or 1 of Portland cement to 3 of sand. If a finish coat is to be

used, fiber may be added to the brown coat in amounts not to exceed

II/2 bushels per cubic yard of sand.

For the finish coat the proportions of lime putty and gypsum

should be left to the discretion of the plasterer.

3. AppUcation. —The scratch coat on lathed surfaces should be

a})plied with sufficient force to push the plaster through the openings in or between the laths, should be of such thickness to cover the

lath at least one-fourth inch, should be brought to a reasonably true

surface, and should be scratched vertically and horizontally. The

scratch coat should be permitted to harden until the pressure of the

thumb is not sufficient to break down the edges of the scratches.

The scratch coat on masonry should be applied with sufficient force to form an effective key with the depressions in the masonry,

sliould then be built up to the desired thickness, and then rodded

to produce a plane surface, flush with the grounds. It should then

be permitted to become thoroughly harsh and dry before the finish coat or other decorative finish is applied.

The brown coat should be applied with sufficient force to provide

a proper key with the scratch coat, should then be built up to the

desired thickness and rodded to produce a plane true surface flush

with the face of the grounds. It is then customary to go over this coat with a plasterer’s darby to take out the irregularities left by

the rod, after which the surface is floated as a final step in making

a smooth and true surface. The floating process also assists in

making the surface of the brown coat sufficiently porous to provide

])roper suction for the application of the finish coat. The finish coat should be spread over the entire area of one side

of the room, except where scaffolds are necessary, and then troweled

just as the cementitious material is hardening. Much skill and care

is needed for success in the application of the finish coat. Par. 44. Number and Thickness of Plaster Coats Necessary.

Plaster on wood or metal lath or on other materials which support

the plaster by keying should be not less than 2-coat work and at least five-eighth inch thick.

Plaster on masonry surfaces, plaster board, or on other materials

which do not support the plaster by keying may be 1-coat work, but

should be of sufficient thickness to cover the surface amply and to correct all unevenness. The exposed aggregate method of making colored concrete is equally applicable'^to plaster and requires merely a little care in the

selection of the sand. Wood fibers used in the brown coat may be

dyed and exposed by washing the plaster after it has set to give

effects in color and texture. The ordinary brown coat may be rubbed

down to a sand-float finish, which is satisfactory for some purposes,

and the appearance may be improved by painting.
76 MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS

Par. 45. Furring.

The furring out of all plaster surfaces from masonry walls is rec- ommended by many authorities. The advisability of this measure

is plainly shown by the following summary of experience reported

from all parts of the country

:

1. In regions subject to low temperature, high winds, heavy rains, or extreme humidity of considerable duration, furring of masonry

exterior walls is practically a necessity to avoid damp walls, also the

danger of ruining wall decorations.

Figuke

20

Methods

of

installing

gypsum

wall

board.
MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS 77

2. Ill arid localities, where low temperatures are infrequent, furring may be omitted without serious results, but should be used

wherever economy in construction cost is a secondary consideration.

3. Waterproofing paints or compounds applied to the interior of

masonry walls help considerably to prevent moisture penetration,

but have little effect in preventing condensation, and make it diffi- cult to bond plaster directly to such treated walls. (See par. 17 of

this appendix for moisture penetration through masonry walls.)

4. Furring is somewhat less necessary on masonry exterior walls

of hollow units, since the inclosed air cells help to check transmission of heat and moisture. However, when the joints run through

the wall there is a possibility that moisture will find its way to the

inner wall surface through cracks and crevices which may develop

between the mortar and the masonry unit.

5. Furring a masonry wall lessens its heat conductivity, thus sav- ing fuel, which saving, of course, continues throughout the life of the

structure and may repay many times over the increased cost of

furring.

G. When walls are built with hollow masonry units and the joints

extend but ])art way through the wall, it is common practice in

many localities to omit the furring and to apply the plaster directly on the Avail.

7. In concreteghouse construction provision for insulation of exterior Avails is recommended. A dead-air space Avithin the Avail itself or formed by furring and plastering has been found effective,

and this re(|uireiiient seems to be favored by those recommending

the use of conci’ete external Avails. In applying ])laster to furring lath it is important that the keys

shall not project through so as to touch the wall nor be allowed to drop off and form a solid mass betAA'een plaster and wall. In either case moistui*e from the Avail is liable to be transmitted through the

plaster i)roducing troublesome results, such as staining the wall and

ruining the lath—Avood lath by dry rot and metal lath by corrosion.

It is claimed that excellent results in furring 8-inch brick walls are obtained by attaching a layer of tarred paper to the back of the

furring strips or by using a lath in which such paper forms an

integral part.

Incombustible furring is excellent, since it entirely prevents a fire creeping along a AA^all from one story to another behind the plaster.

HolloAA^tile or gypsum furring blocks are much used and are quite

satisfactory. They have grooves in the back face which furnish air

spaces betAA^een the AA^^all and the plaster. There are also sev^eral forms of metal furring to Avhich metal lath is attached and which

sei-A^e the same purpose. Where walls are likely to be continuously

damp, hollow tile furring Avill be more satisfactory than gypsum.

Par. 46. Insulation.

Since the first edition of the report was published, rapid strides

have been made in the insulation of dwellings. This subject appears

to be bevond the scope of a building code. Its value m securing fuel

econoiiiv and comfort has come to be generally recognized. Obvioiislv, tiie use of such material may repay many times its initial cost. In general, heat losses from any building occur in two ways—(1)

by infiltration of air around openings, such as doors and windows,
78 MINIMUM SMALL DWELLING CONSTKUCTION KEQUIIIEMENTS

and infiltration through the walls or roof assembly; and (2) by heat

transniission « through the materials of which the walls and roof of

the building are constructed.

In the first case a proper and careful fitting of doors and windows

will materially decrease air infiltration. Ildiere cost considerations

are not too important, the addition of weather stripping will further decrease losses from this source. With respect to frame walls,

air infiltration through the wall itself has been shown to be greatly

decreased by the use of a good grade of sheathing paper. In the

case of masonry walls, furring has been found materially to in- crease the insulating value of the ordinary types of walls.

Heat transmission through various assemblies of materials is known to be decreased b}^ using an insulator either of fibrous materials in loose form or made into quilts confined between relatively

thin layers of paper or textile, or by boards in which the components are bonded together in some way.

The selection of any particular material is dependent upon the

particular needs and requirements in the way of fire hazard, struc- tural strength, cost, etc. The final cost to^ be considered in this

event is not the cost per square foot of any given material, but

rather the cost per unit insulating value of the" commercial thickness.

The following table, taken from Circular No. 376 of the Bureau

of Standards, entitled ‘‘ Thermal Insulation of Buildings,” gives

general information on the approximate fuel savings in dwelling

houses. For more detailed information bearing on this subject

reference is made to this publication.

Table G.—Ai)j)roximate fuel .savings in dirclUng hon^ses

(Expressed in percentage of fuel which would have been required for similar house without insulation or weather stripping)

Saving

Per cent

15 to 20. 25 to 30. 20 to 30. About 40. About 50. 30 to 40. About 50. About 60.

No insulation, weather stripped Same, with double (storm) windows

3^-inch insulation, not weather stripped . )4-inch insulation, weather stripped

V^-inch insulation, with double windows.

1-inch insulation, not weather stripped..

1-inch insulation, weather stripped

1-inch insulation, with double windows. .

(Expressed in percentage of fuel which would have been required for similar house without insulation but

with weather stripping)

With double windows, no insulation

>^-inch insulation only H-inch insulation, with double windows.

1-inch insulation only

1-inch insulation with double windows. .

Per cent

10 to 15. 25 to 35. 40 to 45. 35 to 45. cO to 55.

Par. 47. Party Walls.

The thickness advisable for party walls depends on several factors

not affecting exterior walls. Such separating walls also serve the

For detailed information on heat transmission through walls, see B. S. Jour., vol. G (KP21)1), entitled “ Heat Transfer Through Building Walls.”
MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS 79

purpose of fire walls. The vertical loads, while higher than on

(\xteiuor walls produce no greater stresses, owing to the equalizing

eliect ot noor loads from both sides. More bearing area is lost by

insertion of joists on both sides, and the close proximity of these

reduces the elliciency of thin walls as fire stops.

Party walls of hollow masonry units or hollow walls of brick

because of their lighter weight and the greater liability of destruction in case ol fire as compared with solid masonry walls, are required

to be at least 12 inches thick throughout. Consideration must also be

given to the increased difficulty of inserting joists in such walls and

obtaining siqiport and protection for the ends.

When the building on one side only of a party wall is completed

ydth the wall and where subsequent construction may require breaking into the wall for insertion of floor beams or other members, party

walls built of hollow masonry units or hollow walls of brick should

not be used. '\^ here the disadvantages of breaking into such walls can be overcome—as, for instance, by solid wall construction extending at least one course above and below where the future line of

joists will be inserted—party walls of this type are feasible for the

])urpose intended when constructed under the provisions outlined

in section 4-2, part 2, of this report. Par. 48. Parapet Walls.

The object of a parapet wall is to prevent a fire in a house from

entering an adjoining house through the attic space, also to restrict flames from lapping over and igniting the adjoining roof. Where

party walls do not extend through incombustible roofs, the joints

between the wall and the roof may be effectively closed by metal lath

bent into the angle between wall and roof and plastered with gypsum

or Portland-cement plaster.

Careful workmanship on parapet walls and proper coping is necessary to prevent moisture from seeping down into the wall and

injuring the plaster. Experience with building maintenance has

indicated that the importance of coping has not been generally

recognized, and many otherwise excellent buildings have been seri- ously damaged by a leaking coping. Soldered metal joints extending

through the walls, either exposed or covered with masonry, make an

excellent protection. Par. 49. Roof Coverings.

No direct requirements for roof coverings are included in part 2, owing to the committee’s decision not to consider in this report the

influence upon construction of fire hazards created by building

congestion, as explained in the introduction of this report (p. 3).

Information regarding roof coverings in respect to fire-resistive considerations is contained in the Building Code Committee’s Report,

entitled “ Recommended Minimum Requirements for Fire Resistance

in Buildings.”

Par. 50. Chimneys.'^

Pure quartz gravel or other highly siliceous gravel concretes are not adapted to Avithstand high temperatures, and it is therefore

For complete specifications covering construction and care of low-temperature chimneys,

reference is made to “A Standard Ordinance for Chimney Construction,” distributed

gratis by the National Board of Fire Underwriters, 85 John Street, New York, N. Y,
80 MINIMUM SMALL DWELLING CONSTKUCTION EEQUIREMENTS

recommended that they should not be used for chimne^^s when subject to direct attack of heat.

The reinforcement required in concrete chimneys cast as a unit, or when built of large blocks inclosing more than one flue, is to resist stresses due to temperature variations or unequal settlement of

foundations.

Experience has indicated that good quality flue linings properly

installed are a reliable material and an essential part of all thinwalled chimneys. Care and good workmanship in laying the flue lining will aid in preventing leaky flues having an unsatisfactory

draft as well as an increased fire hazard. Parging the inner walls

of the flue with mortar as the masonry progresses should not be

allowed as a substitute for flue lining. The combined effect of wind,

expansion and contraction due to temperature changes, and flue gases causes disintegration of such lining. It is extremely advisable to construct flues as nearly vertical as possible, since each offset retards draft and offers a lodging place

for soot to accumulate. If it becomes absolutely necessary to change

the direction of a flue, it should not depart more than 30° from the

vertical.

Experience has shown that more than one connection to a flue is bad practice. The draft is impaired and there is much danger,

where only one of the connections is in active use, that fire will be

communicated by way of the unused opening to connecting rooms. Where a connection is not in use there is danger that the flue stop

may be displaced or destroyed by corrosion, thus permitting sparks

to pass through. Such unused connections also accumulate soot,

which in time will burn and thus greatly increase the fire hazard.

Flue linings should project I inches above the chimney top to allow

for a 2-inch wash and a 2-inch projection of the lining. It is important tliat the top of chimneys be properly capped by a 2-inch cement

wash or other suitable means to prevent water entering the masonry

work. Wliere freezing is likely to occur, this may cause disintegration of the ex]iosed part of the chimney. Also the water might find

its way down the chimney and cause discoloration or cracking of the

plaster in the rooms where it was located.

A method of hearth-foundation construction that has proved satis- factory consists of a reinforced-concrete slab supported by steel members cantilevered from the masonry chimney.

In studies conducted by the American Society of Heating and

Ventilating Engineers ® on draft efficiency in lined and unlined round,

square, and oblong flues it was found that round flues provide a better draft than other shapes having equal cross-sectional area and

operating under the came conditions. In flues having a square

cross-sectional area the corners are found to have little, if any, influ- ence on the draft, and the so-called effective area of such a lining

is the same as that of a round flue of equal internal diameter, no

credit being allowed for draft in the dead corners. When square or rectangular flues are used, they should be chosen on the basis of

“ effective area ” as given on page 88.

5 Code of Minimum Requirements for Heating and Ventilating of Buildings, by American

Society of Heating and Ventilating Engineers, 51 Madison Avenue, New York, N. Y.
ivriNnviUM s]\rALL dwelling construction requirements 81

3T/fNDA£D CH/MNEY C0^5T£UCT/OA/

Sca/e in Feet 0 12 3 4 Figure 21

Elevation and section of an interior independent chimney showing recommended

construction. Extra flues can be added as desired.
82 MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS

Details of chimney construction showing method of flashing at roof

surface, also, a wash course, but no cap surrounding flues at top. (See fig. 21.) Underflashing or cap flashing may bo substituted

for copper apron shown.

3^/cAT

/=>/)jery

ij/ul

84 MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS

Ex'

n n n n

N£/iDEB B£/iAt

|

/

4- //\/CH CC£A/e/iA/C£ 3PACE F/LLED MTH LOOSE /A/COMaoST/6LC MATERIAL R\ .. 11- U

1 ^C^AM ^ ml u LJ LI 1 IJ

z. Figure 24

1. Method for building two fireplaces back to back in a brick party wall to secure proper spacing between ends of fioor joists.

2. Floor framing around a single fireplace. Note filling between framing and brickAvork, which serves both as insulator and fire-stop.
MINIM r.M SMALL DM^ELLING CONSTRUCTION REQUIREMENTS 85

LOOS£ /f^COr>jaUST/eL£ MAT£/e//?L AS FZ/SESrOPP^AiQ Figure 25

Method of framing around a fireplace and chimney construction with, exposed hack

wall and chimney.
86 MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS

]] 1 !!

ii

j 1 L_i _j 1 ,>^'song

h

'^}r/B£ eefCK U f \ ^adnl

Tiri'dan^

JJ— 1 B ^120^

IT

£ /A'r-V CL£/ieAA^C£ J/»/?C£ £/LL£0 CJ/TH LOOSE /A^O/V£(/Sr/£L£

A?/9T£e/AL t9S £//?£jrOPP//VG

H£AD£e esp/v

U u

: |33 j bn! : OQ 1 po

np /V£xr COUQSE

/fPPJ30V£0 HOLLOC^ T/L£ CON5TBUCTJON FOP FIPFPLPCF CHIMNEY

Y?PPJSOYFO I^/OOOI^OJPJY PPOTFCTIOf)f

Figure 26

Details of hollow tile chimney construction and of woodwork protection.
MINIMTTIM SMALL D\VELLING CONSTRUCTION REQUIREMENTS 87

a

3

Figuee 27

1. Floor framing around chimney in a party wall, to secure proper space between

ends of floor joists.

2. Ordinary floor framing around a chimney. All timbers 2 inches clear of brickwork and space filled with fireproofing material.

3. Stud partition across back of a chimney showing proper method of arranging studs.

4. Stud partition across back of a fireplace and around the ends of the chimney

breast, showing proper arrangement of studs. Method of fire-stopping this space is shown on chimney section, Figure 21.
88 MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS

J^OCf/VD FLU£

l/N/m

/VO C/2SD/TFO/5

DJ9FFT //V D£FD

CO/S/V£/SS

fVO C/SED/T FO/3 OG/?FT

//V OEFO CO/^/V£/^S Figure 2S

Details of effective area of flue linings. Ddia an flues, areas, and chimneys with and without flue linings

Round

flue lining

(inside diameter)

Nominal sizes

Rectangular flue lining (outside dimensions) (inches)

Unlined chimneys (in- side dimensions)

(inches)

Actual

inside area

Effective area “E”

Mini- mum

thick- ness of chimney

wall

Square Square

Inches inches inches Inches

4 by 8 32 11.

1

4 by 12 48 19.

1

4J4 by 8H-- 23.6 21. 3 354

6 28.3 28.3 3^

8 by 8 64 28.3 8 7H by 7H 39. 1 30.7 Wa

41/2 by 13 38. 2 35.9 3M

8H bv 8H 52. 6 41.3 3^

8 50.3 50.3 3*4

8 by 12 96 52.3 8 8H by 13 80. 5 70 3M

10 78. 5 78. 5 3M

12 by 12 144 78. 5 8 8H bv 1714 106 96. 5 3M

13 by 13 127 100 3M

12 113 113 3^

12 by 16 192 126 8

13 by 1734. 177 150 354

15 177 177 3%

1734 by 1714 233 183 20 by 20 298 234 8

18 254 254 8 20 by 24 357 295 8

20 314 314 8

24 by 24... 461 346 8

22 380 380 8

24 4.52 452 8
iVIINlMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS 89

\ arioiis studies on the height of chimneys for dwellings indicate

that the niinimum height should be between 30 and 35 feet. While

dwellings of the bungalow type and other 1%-story houses have

chimneys less than this height, if a good draft at all times is desired

chimneys less than 30 feet in height are not desirable, as drafts

in such chimneys are likely to be erratic in their action.

For fireplaces it k especially important for good draft to design

the flue on the ‘‘effective area” principle, and an effective area of

flue of one-twelfth of the area of the fireplace opening is desirable.

A sinoke test of the chimney is recommended before its acceptance. The method of test is to build a smudge fire at the bottom

of the flue and while smoke is flowing freely from the flue to close

it tightly at the top. Escape of smoke into other flues or through

the chimney wall indicates openings that should be made tight before

the chimney is accepted.

In the foregoing pages are shown elevations and sections of

typical chimney and fireplace construction supplied through the

courtesy of the National Board of Fire Underwriters, and which

are at least equal to the requirements given in sections 10-1 and

10-2, part 2. Par. 51. Heating Appliances.

A 1 ‘eview of the origin of fires in dwellings indicates that many

of them are caused by overheated smoke pipes, by placing heating

appliances too close to combustible construction, and by poor maintenance. Many of the requirements written in the past for the pur-

])ose of controlling the hazards causing these fires have been based,

for the most part, on the judgment of those experienced in fire protection and fire underwriting. Actual test data have been available to a very limited extent. The Building Code Committee, believing such data to be essential for the formulation of practical

and economical code requirements, requested the Bureau of Standards to conduct tests on these appliances with this purpose in mind.

Under the direction of S. H. Ingberg a series of such tests have

been conducted by G. Q. Voight, of the bureau. In order to establish experimental conditions closely related to typical installations, a survey was made of equipment in use in the District of Columbia,

as well as a survey of the causes of fires from household equipment

for the period 19&-1930. With this information as a guide, some

34 individual tests were made on different assemblies of appliances.

In general, temperatures were determined at critical points for

smoke pipes, stoves, and furnaces in order to discover their potential fire hazard with respect to partitions, floors, and ceilings within

various distances, either unprotected or protected.

Where wood is heated for short durations to temperatures in the

range of from approximately 482° to 572° F., ignition may result. No definite cases of ignition of wood exposed for long periods

around heating installations were found where temperatures were below 300° F. Between temperatures of 300° and 375° F. browning

and initial charring may occur, but, in so far as direct evidence is concerned, ignition has not resulted from these temperatures. The

danger when combustible construction is heated for long periods is 126381°—32 7
90 MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS

that, by a process of slow carbonization, a condition may gradually

be produced favoring ignition at lower temperatures than would re- sult from shorter periods of heating. As a basis for interpreting

the test data in this formulation of requirements, a temperature of

300° F. has been assumed as the maximum allowable even for short

infrequent periods of exposure.

2. Smoke pipes and thimbles. —The actual temperatures at the

surface of wood joists spaced at 6, 10, and 12 inches from smoke

pipes indicated that at least a 12-inch clearance should be maintained between such pipes and unprotected combustible construction.

Keductions in this distance should be permitted only when protection of asbestos board or equivalent approved incombustible material

is used.

Because of the increased likelihood of open joints where long runs

of horizontal pipe occur, much less hazardous conditions can be ef- fected by short runs well supported and wdth tight riveted joints.

In the thimble tests the data obtained showed that the ordinary

thimble available commercially, providing a 1-inch ventilated air

space around the smoke pipe, offered insufficient protection. With

a thimble 8 inches larger in diameter than the smoke pipe having a vented air space, or a thimble I inches larger in diameter than the

pipe with the space between tlie pipe and thimble filled solidly with

insulating material, such as mineral wool, temperatures approximately at the maximum from safety considerations were obtained.

A thimble 8 inches larger in diameter than the smoke pipe filled with insulating material gave temperatures that would provide a very considerable factor of safety. It should be borne in mind that

the tests represent extremely severe conditions, but that conditions

of this nature can and do obtain.

3. Wall and partition protection . —To insure that excessive temperatures will not occur on the surfaces of wall and partitions adjacent

to stoves or ranges burning solid or liquid fuel, a clearance of 21

inches between these appliances and combustible studding or sheathing appears necessary where no protective covering is employed.

When shields of incombustible material extending at least 1 foot on all sides and from the floor to at least 1 foot above the stove or range are j^i’ovided, the clearances can be reduced one-half. In the

case of plastered construction having combustible supports, these as well as any combustible j)laster base should have a clearance of at least 18 inches Avitli an allowable decrease to 9 inches where bright

metal or equivalent protection is applied over the plaster.

The tests indicated that the difference in performance between

black iron and galvanized iron used as a shield to protect combustible construction is very marked, both as applied directly to the wall

and as forming one side of closed air spaces. Galvanized iron will,

with time, lose some of its heat reflecting properties, although it is not known to what extent this would occur. ^letal initially brighter

than galvanized iron that would retain this property would apparently give greater protection than that obtained in the tests.

4. Floor protection . —Heating furnaces, boilers, laundry stoves, or similar devices in which hot fires may be maintained should rest upon masonry foundations.
MIXIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS 91

When it is necessary that stoves or ranges without legs and which

burn solid or liquid fuel be set directly on wood floors, the floors should be protected by a hearth consisting of at least one course of

brick on edge or other masonry of the same thickness. This hearth

should extend not less than 6 inches on the sides and rear, and it is well to have it extend at least 2 feet in the front in order to prevent

hot coals from falling on the floor. The necessity for protection

decreases as the distance from the surface of the floor to the bottom

of the stoves increases. In the tests a clearance of 5 inches between

the floor and stove, when the floor was covered with one-quarter inch

of asbestos board overlaid with black iron, gave temperatures close to the end point for safety considerations. Inasmuch as the bottom of a sheet-metal stove may fall out from deterioration of the metal, it is always wise to set such stoves on some sort of an incombustible

covering. (See also par. 52 of this appendix.)

5. Warm-air pipes. —Interpretation of the test data for warm-air

furnaces shows that some protection of these pipes is essential where

conditions are severe. The number of fires caused by overheated

warm-air ducts is comparatively small. The requirements for warm

pipes given in section 10-3, part 2, are considered sufficient for conditions producing maximum temperatures.

Where pipeless furnaces are installed, a distance of at least 3 feet from the top of the radiating dome to the finished floor surface is desirable. The down draft of cold air at the sides of the register was found to reduce the temperature of the air from the warm-air

flow to a very marked extent. The temperatures measured on combustible floor construction adjacent to register boxes connected with

this type of furnace were not high enough to be hazardous. Temperatures sufficient to cause eventual ignition of combustible material

or goods were found to exist in the path of the warm-air flow at the

top of the register. Partitions should never be built over registers, as is sometimes done to facilitate heat distribution. Furniture,

rugs, clothing, or other combustible materials placed on a warmair register introduce a very definite fire hazard which can be easily

avoided. • 6. Steam and hot-water pipes. —Experienced observers have ex- pressed the belief that after a period of long-continued heating combustible construction in contact to steam or hot-water pipes may be

subject to spontaneous ignition. No test data on this are available.

Simple precautions, such as preventing any direct contact between

combustible construction and steam or hot-water pipes, covering the

pipes with some form of insulation, and, where they pass through

combustible floors or partitions, providing a metal sleeve for the

pipe, are desirable. Some authorities recommend that these pipes

be kept an inch away from combustible construction. Par. 52. Fire-Resistive Requirements.

Where an ultimate fire resistance of one hour is referred to in

sections 9 and 10, part 2, the fire-resistance rating of the materials

and construction assembly involved, as determined by tests made

in accordance with the Specifications for Fire Tests of Materials

and Construction A2-1926 of the American Standards Association,

is meant. These standards are the ones employed by the Bureau of
92 MINIMUM SMALL DWELLING CONSTEUCTION EEQUIKEMENTS

Standards, the Underwriters’ Laboratories, and other testing authorities in the conduct of fire tests on building construction materials

and assemblies.

For the sake of clearness a typical construction having a 1-hour

ultimate fire resistance has been given in the requirements in part

2, and any other construction meeting the requirements for 1-hour

ultimate fire resistance is of course permissible.

In the case of walls and partitions the following constructions

have been listed as having a 1-hour rating in the committee’s report

entitled ‘‘ Eecommended Minimum Requirements for Fire Resistance

in Buildings,” and this report should be consulted wherever a more

thorough investigation of fire-resistance ratings becomes necessary:

3% inches or more clay or shale brick. 3% inches or more concrete or sand-lime brick. 3 inches or more hollow gypsum block, nnplastered.

2 inches or more solid gypsum block, plastered both sides. 4 inches or more cinder concrete block, nnplastered ; or 3 inches or more

plastered on both sides. 3 inches or 4 inches hollow clay tile, plastered on both sides. 3 inches or more solid reinforced concrete, nnplastered, reinforced in both

directions with not less than 0.4 of 1 per cent reinforcement. Maximum size of coarse aggregate not to exceed % inch. 2 Y2 inches or more solid partition of Portland-cement plaster on expanded

metal or wire lath on incombustible studding.

2 Y2 inches or more solid partition of sanded gypsum plaster on expanded metal

lath on incombustible studding.

2% inches or more solid partition of sanded gypsum plaster on wire lath on

incombustible studding. 2 inches or more solid partiton of sanded gypsum plaster on expanded metal lath or wire lath on incombustible studding.

Hollow partition of at least %-inch neat tibered gypsum plaster on at least %-inch gypsum ])laster board on each side of incombustible studding.

Hollow partition of at least V-»-iuch wood tibered unsanded gypsum plaster on

at least %-inch gypsum plaster board on each side of combustible studding,

tire stopped. Joints of plaster board covered with expanded metal lath at

least 3 inches wide. Hollow partition of at least %-inch gypsum plaster on expanded metal lath on each side of combustible studding, tire stopped.

Hollow partition of at least %-inch Portland-cement plaster on expanded metal

lath on each side of incombustilde studding, or on wire lath oineach side of incombustible studding, or on expanded metal or wire lath on each side of combustible studding.

Hollow partition of at least %-inch gypsum plaster on expanded metal lath on each side of incombustible studding.

Hollow partition of at least %-inch gypsum plaster on wire lath on each side

of incombustible studding.

In the case of floors and ceilings, constructions having a rating of one hour or more are listed in the report mentioned above, as follows

:

3% inches or more reinforced concrete slabs or arches having at least %-inch

protection below steel reinforcement. Composite floors consisting of reinforced concrete beams with filler of hollow

tile, cinder concrete block, slag block, or gypsum block, thickness of filler to be 6 inches or more if without top slab, plastered, or 4 inches or more if with 2-inch or more concrete slab ; at least %-inch concrete protection for

steel reinforcement.

Concrete-joist construction, not more than 24 inches between joists ; thickness

of slab 2 inches or more if with ceiling of at least %-inch gypsum or Port- land-cement plaster on metal or wire lath or 3 inches if without ceiling; at

least %-inch concrete protection below steel reinforcement.

Steel-joist construction consisting of a 2-inch or more reinforced concrete or gypsum top slab and at least a %-inch gypsum or Portland-cement plaster

ceiling on expanded metal or wire lath.
MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS 93

Wood-joist construction, fire stopped, with double board fioor having insulat- ing layer between boards and with ceiling of at least %-inch gypsum plaster on expanded metal lath. Wood-joist construction, fire stopped, with double board fioor having insulat- ing layer between boards and with ceiling of at least %-inch Portland-cement

plaster on expanded metal lath. Wood-joist construction, fire stopped, with double board fioor having insulating

layer between boards and with ceiling of at least %-inch gypsum or Portland- cement plaster on wire lath. AVood-joist construction, fire stopped, with double board fioor having insulating

layer between boards and with ceiling of at least %-inch wood fibered gypsum

plaster on at least %-inch gypsum plaster board. Joints of plaster board

covered with expanded metal lath at least 3 inches wide. Statistics on fires in dwellings indicate that a large number of

these fires originate in the basement. Such fires originating at night

have often gained such headway before being discovered that the

occupants have either been trapped on the second story or have been

compelled to jump from the windows. Wlien it is remembered that

most dwellings now have but one stairway, the desirability of confining tlie fire to the point of origin as long as possible is easily seen. To accomplish this purpose it is desirable to have the first floor built of incombustible construction, or of a combustible construction

as described in this paragraph which has a fire-resistance rating of

at least one hour.

If it is not feasible to attempt this because of cost considerations, a fire-resistive ceiling directly over the heating plant will reduce

the hazard somewhat.

Sprinkler systems are also available that may be installed in the

entire basement or in aii}^ portion thereof. Their use in locations

of this nature is a distinct aid in preventing serious fires. Par. 53. Importance of Fire Stops.

The committee desires to emphasize the fact that fire stops are an extremely important though inexpensive aid in preventing rapid

distribution of fire. Fire in buildings spreads by the movement of high-temperature

air and gases through every open channel. In addition to halls,

stairways, and other large spaces, these heated gases also follow

with equal facilit}^ the concealed spaces between floor joists, between the studs in partitions and walls of frame construction, and

betAveen the plaster and the Avail Avhere the former is carried on

furring strips. In a clAvelling or even in a large building where

these hidden channels are not obstructed at suitable points, a fire

AA’iU find its AA^ay in a feAA^ minutes to all parts of the structure, and

either Avill destroy it entirely or will result in much greater loss than would liaA^e occurred if fire stops had been installed. It is not practical to introduce cut-offs in hallways and stairways

of the ordinary small-size dwelling, but fire stopping of all hidden

channels is eas}^ to accomplish. . .r, 1 In general, fire stops should be so located as to separate the

open spaces ^vitlnn the walls and floor of each room from those of

adjacent rooms. Especial care should be taken to slmt off the cellar or basement from the first floor. A large proportion of residence

fires start in such lower stories where the heating equipment is located and are readily communicated to all parts of the structures by way of hollow partitions and walls and the spaces around warm-
94 MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS

air ]Dipes and floor registers. Hence the importance of having them

all carefully Are stopped.

2. Wherever possible, fire stops should be of incombustible material and should form a practically air-tight obstruction, for the

hot air and gases generate pressure and will find their way through

very small crevices.

3. Precautions such as described above, by delaying the spread of

fire, will afford time for help to arrive, and result in saving many

buildings and even lives which otherwise might be lost.

4. Experiments upon the thermal conductivity of walls indicate

that heat losses are appreciably decreased by breaks in the furring

spaces at each story, and that fire stops, in addition to tlieir normal

functions, save fuel.

5. Fire stops, if properly installed, provide a valuable barrier

to rats and other rodents. Par. 54. Vigilance Necessary to Secure Fire Stops.

The greatest obstacle to securing efficient fire stops in a building

is in getting architects and builders to realize the supreme importance of such precautions. The ordinary carpenter or builder is ignorant of the serious annual life and property loss due to fires in combustible dwellings, and considers the possibility of such a

fire too remote to worry about. Some one must be responsible for

rigid inspection to insure that such work is concientiously performed. Wherever possible the building inspector should be re- quired to inspect all fire stopping before it is concealed from view.

Usually the owner lacks experience and does not know what should

be required. Par. 55. Fire-Stopping Materials.

1. Tavo courses of brick, tile slabs, or other masonry are required

to cut off a furring space, for mortar joints may drop out of a

single course and render it useless.

2. Incombustible material suitable as dry fill for fire stopping may

be crushed refuse mortar, plaster, concrete, holloAv tile, gypsum

block, or other similar material containing sufficient fine stuff to fill voids Avhen it settles. Loose boiler cinders is one of the best

fire-stopping materials, and a mixture of sand and gravel with cinders or ashes, or eA^en dry earth, Avill also seiwe the purpose. The

Aveight of sand or graA^l alone or of crushed concrete Avould be

objectionable AAdien supported on metal lath. Some of these materials are ahvays found about a neAV building, and their use involves no expense except for labor.

3. Gypsum blocks are excellent for fire stopping in dry locations.

Ordinary partition blocks can easily be saAA’ed to fit any space. Any

open joints betAA^een such blocks should be mortar filled. Gypsum

products, hoAveA^er, should not be used Avhere likely to become wet. Under such conditions it Avould be liable to induce dry rot in adjoining woodAvork. Metal lath and plaster is also excellent fire- stopping construction, especially where considerable surfaces are

to be coA^ered.

4. Metal lath is a coiiA^enient and inexpensive material for supporting fire-stopping material betAveen studs or joists. It can be easih^
MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS 95

Figure 2d.—DivcIUngs with Walls of Brick or Other Masonry

1 Method of fire stopping at eaves when attic floor joists are level with

plate ; 2. Same as 1, except that attic floor joists are any distance below

the plate and built into the wall. Support for fire stopping might be same as in 1 if more convenient ; 3. In this and the other figures of this

plate, note fire stopping of wooden furring by two courses of brickwork

being set out to face of furring above and below floor joists all around the

building. Other types of masonry walls should be built out in the same manner ; 4. Fire stopping at a floor level when the wall is thinner above

the floor than below.
96 MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS

bent into shape to fit such spaces and then nailed to place. To

avoid having the fine material sift through the lath, it is best to cover it with a layer of plaster or mortar before applying the fill material. Such fire stopping will yield with the shrinkage of the

woodwork and always maintain its full protective efficiency.

1 and 3, Elevation and plan showing fire stopping of wall of frame building

at line of sill and between studs and floor joists.

2. Fire stopping with timber cut between floor joists on top of brick partition.

4. Fire stopping of partition resting on wooden girder.

5. Same as 2. except that incombustible compressible material between tuo

boards is used instead of a timber.

5. There are some places, such as between floor joists resting on

a brick cellar partition, wliere concrete fire stopping should not be

used, because the shrinkage of the timber joists Avill bring the

flooring to bear upon the rigid fire stopping and the floor will bulge.

Metal lath and plaster could also be used if proper precautions were taken to insure complete cut-offs.
MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS 97

C. Metal lath and cement or gypsum plaster are excellent fire- stopping construction for the under side of a box cornice or a flat finish under the eaves.OLfnWE SHEATHING

PAPER. OR PELT^ EtHWGLE^ OR. CIAP30ARDS

mcoridYfbLP

MAIT^/AL

TH & PLASTER.

Scale

FLOOR jorsf^

^'^^4 IN. stud

^ 'Ve IN. BOARD

%ZlN.

oo F

: /V. atvd

0 ft

1 II0 N 1^10 -w7 I material.

’PPER FLOOR. DEAFENING FELT UNDER FLOOR..

a-

<3k4!N. TOHOLBCTIRE’STOPPG, CROSS-FURRING LATH AND PLASTER, /» StN. RIBBON GIRT

ii*ZlN. NAILING -piECE FLOOR JOtST~^ —2*4- IN. STUD

4« -Ve/N.e>oARD

TO HOLD riRE-SlDppINQ

^ tZm. NAILING piECE FLOOR JOIST 'z*4iN.'S>ruD

Figure 31

1 and 8. Elevation and plan showing fire stopping in frame wall at con- nection of upper floor joists with girt. 2 and 4. Fire stopping at same place for “ balloon frame.” Note.—Wherever boards are indicated as supports to hold incombustible

fire stopping in place, metal lath is recommended as a superior substitute.

It is easier installed and will not burn.

7. Fire stopping around warm-air pipes and registers is important,

but seldom done. Any such space should be fire stopped irrespective

of floor construction. In fireproof floor construction, register boxes

should fit the floor opening snugly, and so make fire stopping un-
98 MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS

1. Interior partition running same direction as floor joists supported on

double joists, fire-stopped at l)ottoin by 2 by 4 inch sole. 2 and 6. Elevation and plan of partition footing on 3 by 4 inch cap of partition below running crosswise to joists, showing method of fire stopping between joists.

3. Partition running crosswise to floor joists footing on sole used as a fire- stop. This would be improved by addition of some incombustible

material on top of sole. 4 and 5. Elevation and plan of partition running same direction as floor joist footing on 3 by 4 inch cap of pai-tition below used as a fire stop, and floor joists placed alongside studs. 7 and 8. Elevation and plan of partition running crosswise to joists footing on sole fitted between joists at bottom arid fire-stopped with mineral wool between two boards. Brickwork or other solid incombustible material could be used.
MINIMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS 99

necessary. The protection of woodwork, as elsewhere required

around a register, will safeguard the wood from the heat of the

pipe itself, but the open space provided around the pipe and register

box forms an easy entrance for fire occurring in the lower story to

gain access to the story which the register serves. (See fig. 33, 1 and 2.) Par. 56. Garage Construction.

Walls and partitions and floors and ceilings for private garages

combined with dwellings may be called upon at any time to resist a fire starting in such a location. A minimum rating of one hour

ultimate fire resistance has been required for these locations, and
100 MINIMUM SMALL DWELLING CONSTEUCTION EEQUIREMENTS I

1. Connection of floor joists with outside “ balloon ” frame. Method

of fire-stopping cornice and “ gambrel ” roof construction. Metal

lath and cement i)laster or stucco would make better fire protection than wood for the flat surface under the eaves.

2. Connection of floor joists with outside “ balloon *’ frame at plate

level, showing “ box ” cornice, gutter trough, and foot of roof

rafters, and method of fire stopping. This retards fire entering

building if cornice burns. Same methods employed for girt framing.
I ^MINIMUM S:\IALL DWELLING CONSTRUCTION REQUIREMENTS 101

constructions meeting this requirement have been given in paragraph

52 of this appeiulix.

Koof construction should be equivalent to that for overhead floor and ceiling.

Only products approved by competent authorities should be used.

A large variety of fire doors and windows have been tested and

approved by the Underwriters’ Laboratories and are a standard

commodity in the building-material market. Only fire doors and

windows thus apjiroved or which have withstood tests of equal se- verity conducted by other responsible parties should be used for the

purposes mentioned in section 10-5, part 2. It is important, however, that such devices should be installed in metal frames and with

hardware, the same as that with which they are equipped when

tested; otherwise they may fail to meet expectations when subjected

to fire. Fire doors are made in both swinging and sliding types,

and many of the former are as artistic in appearance as wood doors.

A self-closing fire door as required in section 10-5, part 2, is one

that is normally kept in a closed position by some mechanical device.

Wired glass is excluded from this door because such glass is liable to soften and sag from its fastenings at a temperature of about 1,600° F.,

which is a heat easily produced by burning gasoline or oil. Although provision is made in section 10-5, part 2, for entrance

from the dwelling into the garage, it is recognized that even with

the precautions specified some fire hazard still exists, and it is strongly recommended that when a garage is placed underneath or attached to a dwelling there should be no opening whatever between

the two occupancies. It is much safer to enter the garage from the

outside. Par. 57. Developments in Construction.

The committee recognizes that much research has been and is still being made with a view to developing new types of construction

for dwellings. New materials and new forms of old materials are

also constantly being put on the market. Sound and meritorious

advancements in this field should be recognized promptly in order

that the potential home owner may have the benefits of reduced costs through elimination of waste at many points.

In this respect attention should be directed toward building codes

from tAvo standpoints: (1) That their provisions deal with safety

in construction rather than specifying best methods of construction,

and thus act toward encouragement of new methods rather than

blocking all progress in this direction; and (2) that when necessary

their provisions be brought up to date in order that desirable leplation may not lag too far behind construction progress, thus

causing unnecessary expense and even seriously hindering logical

Committees of experts from all parts of the country chosen to study the problems relating to the purchase, building, equipment, and

other features related to homes, and known as the Presidents Conference on Home Building and Home Owner^ip, made tenatiye

reports of their findings in December, 1931. The

various committees of this conference contain much detailed and
102 MINIMUM SMAUL DWELLING CONSTRUCTION REQUIREMENTS

valuable information on the many subjects which were considered.

Information concerning these reports may be obtained by addressing

the President’s Conference on Home Building and Home Ownership,

Commerce Building, Washington, D. C. Par. 58. Plumbing.

Kequirements for plumbing in dwellings, as well as other buildings, have been issued by a special subcommittee on plumbing of the

Building Code Committee. The most recent publication of this committee, entitled “ Kecommended Minimum Kequirements for Plumbing,” contains detailed plumbing regulations, as well as an appendix

giving much other useful information in this field. Par. 59. Electrical Requirements.

Proper electrical installation is essential to prevent unnecessary

fire hazard. The requirements of the “ National Electrical Code,”

being the Regulations of the National Board of Fire Underwriters

for Electric Wiring and Apparatus as approved by the American

Standards Association, are generally accepted as the most approved

methods and practices. Par. 60. Value of Publications.

The following is a partial list of national and in some cases local organizations, the publications of which have come under observation

of the committee

American Concrete Institute, 2970 West Grand Boulevard, Detroit, Mich.

American Face Brick Association. 130 North Wells Street, Chicago, 111, American Institute of Steel Construction, 200 Madison Avenue, New York, N. Y. American Society of Heating and Ventilating Engineers, 51 Madison Avenue,

New York, N. Y, American Society for Testing ^Materials, 1315 Spruce Street. Philadelphia, Pa. American Standards Association, 29 West Thirty-ninth Street, New York, N. Y. Asphalt Shingle and Hooting Institute, 2 AVest Forty-fifth Street, New York,

N. Y. Associated Tile ^Manufacturers, 420 T.exingtoii Avenue, New York, N. Y. Building Stone Association of Indiana (Inc.), Bloomington, Ind. California Redwood Association. 405 Montgomery Street, San Francisco, Calif. Clay Products Association. Ill AVest AA'ashington Street. Chicago, 111. Clay Products Institute of America, 900 Colonial Building, Philadelphia, Pa. Common Brick Manufacturers’ Association of America, 2121 Guarantee Title Building, Cleveland. Ohio. Gypsum Association, 211 AA>st AAhicker Drive, Chicago, 111. National Board of Fire Underwriters, 85 .Tohn Street, New York, N. Y. National Building Units Corporation. 1000 Arch Street, Philadelphia, Pa. National Fire Protection Association, 00 Batterymarch Street, Boston. IMass. National Lime Association. 927 Fifteenth Street NAA’’., AA'ashington. D. C. National Steel Fabric Co., Union Trust Building. Pittsburgh, Pa. National Lumber Alanufacturers’ Association, 1337 Connecticut Avenue, Washington, D. C. National Sand & Gravel Association. Alunsey Building, AA'ashington, D, C. National AA'arm Air Heating Association, 3440 A. I. U. Building, Columbus, Ohio. Portland Cement Association, ,33 AA'est Grand Boulevard. Chicago, 111. Red Cedar Shingle Bureau, 4445 Stuart Building, Seattle, AA^ash. Sand Lime Brick Association. Saginaw, ]Mich. Structural Clay Tile Association, 1400 Engineering Building, Chicago. 111. Southern Pine Association. Interstate Bank Building. New Orleans, La.

Steel Joist Institute, 1730 Dime Bank Building, Detroit, Mich.

Underwriters Laboratories (Inc.), 207 East Ohio Street, Chicago, 111.
MINIxMUM SMALL DWELLING CONSTRUCTION REQUIREMENTS 103

West Coast Liiiiil)eriiieirs Association, White-Henry-Stuart Building, Seattle, Wash.

Weyerhaeuser Forest Products, First National Bank Building, St. Paul, Minn.

The Building Code Committee desires to call attention to the

large number of j)ublications distributed by national and local

organizations included in the above list for the purpose of promoting

correct practice in the use of their products. The- committee does

not necessarily agree with nor should it be quoted as indorsing the

statements made in such publications. It believes, however, that the

helpful information contained therein should be given careful con- sideration by those interested in building.
!\

\
INDEX

Aggregate:

('oarse Fine

Anchors: For masonry veneer For roof structures For unphxstered buildings.. For walls For wood joists and girders. Appendix, purpose of Arches: Over wall openings Trimmer, under hearths

Areas. See Floor areas.

Page

11,41

11,41 13,43

7, 16, 60, 6160 16,61

1626

-- 9, 11, 12

.. 21,80,81

Back-plastered construction... 14,45 Basement: Columns. g Walls. See Foundation walls. Bearing: Capacity of soil 7, 30 Courses in hollow walls ’ lo For ends of wood joists.. 16,51 For foundation walls 7,30-32 For timber lintels 9, n, 12 Bonding:

Brick walls, solid 8,9,34 Concrete walls... 12,41-43 Hollow walls of brick 10, 39 Walls of hollow masonry units 10, 38 Bracing for frame dwellings 13, i4, 60 Brick, quality of 8, 28, 32 Brickwork. See also Masonry. Bonding of 8,34,37 Laid in freezing weather 37 Load-carrying capacity 34 Reinforced.. 34 Weight of. 27 Bridging: Floor and roof beams 16 In back-plastered construction 45 C

Ceilings: In apartments over one another 18, 92, 93 Cement:

Natural, use permitted 8, 33 Quality of 8,28,33 Special masonry... 33 Chases and recesses: In brick walls 9, 11 In concrete walls 12 In walls of hollow masonry units 11 Chimneys:

Built on masonry supports 19 Combustible construction around 21,22 Construction of 19, 20, 21, 79-89 Corbeling.. 19,80 Flue lining required 19, 20, 80 Height above roofs 19, 89 Inwalls 20 Of concrete 20,80 Roof connections 21, 82, 83 Smoke test advisable 89 Thickness of walls 19, 20, 21 Cinder block. See Hollow masonry units. Columns, basement 8 Concrete:

Mi.xes 11,41 Plain, defined 6 Reinforced, defined 6 Concrete block. See Hollow masonry units. Concrete brick. See Brick. Concrete tile. See Hollow masonry units. 126381°—32 8

Concrete dwellings: Of block or tile Height limited Monolithic type Party walls Structural frame type Unit construction Construction developments.

Page

... 12,4112

... 12,42

... 17,78

13, 42, 43

12, 13, 42

101 D

Dead load defined 5 Definitions I 5 q Drainage for foundations 31 32 Dwelling defined ’ 5 Dwellings, report limited to. 3, 6, 7, 8, 9,'ii, 13, 17, 19 E

Earthquake 35

Electrical regulations 102

Faced wall: Bonding.... jq 40

Definition. 5 Fiber board II*”" 71 Fire door, definition IIIII.II 5 Fire doors for built-in garages 11**24, 101 Fire limits not considered in report 3, 79 Fireplaces, requirements for ’ 21 Fire protection: For built-in garages 24, 101 For heating appliances 22, 23, 89-91 Fire resistance: Ratings of floors and ceilings 18, 24, 92-93 Ratings of walls and partitions 17, 92 Standard fire test 91

Fire-resistive construction:

Ceilings and floors 18, 91, 92 Partitions 24,92,99 Roofs 24,92,101 Walls 17,18,24,92,99 Fire stopping: Adjacent to floor beams 23, 96 For cornices 24, 95, 100 In exterior walls 23, 97, 98 In furred walls 23, 95 In partitions 23,98 In stairways 24 In studded off spaces 23 Inspection 24,94 Importance of 93 Materials for 94 Vigilance necessary to secure 94 Flashing: Around chimneys 21, 81, 82 For masonry veneered dwellings 13, 43 For stucco surfaces 14, 44

Floors: Area 26 Data on design 29, 30, 47, 48 Loads, minimum allowable 6, 7, 49, 51, 52 Systems in concrete dwellings 13, 30 Table of joist sizes 48, 49 Flooring, double, advisable 52 Flue linings: Laying 19,20,80,81,88 Required for chimneys 19, 20

Size 19,88 Foundations: Bearing for 7,30,31 Drainage for 31, 32 Footings 7,31 Materials 7 Of concrete 7 Thickness 7,30,31 Ventilation of 8,32 105
106 INDEX

Frame dwellings: Page

Allowable height 6, 26, 27 Defined 6 Exterior walls. 14 53-63 Foundation walls 7, 8, 58 Veneered with masonry 13, 43 With stucco exterior 14, 44 Framing. See Wood framing. Furnace:

Installation 22,23,90,91 Smoke pipes 22, 23, 89, 90 Furring: Advisability of 76,77 Around chimneys 21, 22, 81, 84, 85, 86, 87 Methods 77 G

Garage: Attached or built-in 24, 25, 99 Defined 6, 99, 101 Girder: Live load on 6,

Wood, size of 48, 49, 51 Grade defined 5 Gypsum block: For furring 77 For fire stopping 94 Partitions 19 Gypsum plaster characteristics 72, 73 Gypsum plaster board 72 Gypsum wall board 71 H

Hearth, requirements for construction 21,80 Heat appliances. 22, 23, 89, 90, 91 Height defined... 5 Height of walls: Concrete 6, 12 Frame 6 Foundation. 7, 8, 26, 27 Hollow, of brick 6, 10 Of dwellings.. 6, 26, 27 Of hollow units 6, 10

Solid, of brick 6. 8, 34 Hollow masonry units, quality of 9, 28, 37, 38 Hollow walls of brick: Allowable height 10,38 Bonding 10,39 Thickness 10,39 Use for party walls 18,79 Housing re(iuirements not included 6 Hydrated lime. See Lime.

Insulation — 77 J

.Toists: Anchored 16,35 Dimensions 16,48,49 Supported, in frame dwellings 13, 16, 53-58 L

Lath: Metal 14,17,18,72 Wood... 72 Lime:

In mortar. 8,33 In plaster 72 Quality of 8,28 Limitations: Of requirements 6 Of floor areas 26 Lining for chimneys 19, 20, 80

Lintels; Definition... 5 In brick walls 9 Of hollow masonry units 11, 39 Load:

Carrying capacity of walls 34 Dead, defined 5 Floor 6, 7 Live, defined i 5 Kemoval of overloads 47 Roof 7,30 Lumber. See Timber.

. , M Page

Masonry:

Ashlar 7,

Brickwork 8, 9, 32, 34, 35, 36, 37 Construction 8-12, 32-43 Definition.. 5 Facing 10, 40 HoUow units 9, 10, 37, 38 Hollow walls 9, 10, 39 In party walls or partitions 17, 79 Materials 8, 9, 11, 28, 32, 37 Alortar g, 33 Piers 9, 10, 12, 32 Protection against freezing 37 Stone 7, 9 Stucco on 44 Veneer 13, 43 Materials: In foundation walls 7 Quality of 8, 9, 11, 14, 28 Weights of 27 Metal framing 17,64,66 Metal lath. See Lath. Mortar: Cement 8, 33 Cement-lime 8, 33 Lime 33 Proportioning 8, 33 Required for walls 8, 33 N

Nominal size does not govern design. 46 P

Parapet walls, general requirements 18, 79

Partitions: Bearing. 16,17,18

Fire resistive, for garages 24, 92, 99 Fire stopping of 23, 93, 94, 96, 97, 98 Nonbearing 17, 18, 19 Weights of 27 Party and division walls: Hollow, of brick 18,79 Of concrete 17,79 Of hollow units 18, 79 Separation of joist ends 18, 84, 87

Solid, of brick 17, 79

Piers: Definition...’ 6 Of brick.. 9 Of hollow masonry units 10 Stone 32 Pipes: Chases for 9, 11, 12 Hot-water 91 Smoke 22,90 Steam 91 Warm-air 22,91

Plaster: Desirability of. 70 For fire resistance 17, 18, 24, 92, 93 General information... 70-75 Ready-mixed 73 Thickness 75 Phxster board. See Gypsum plaster board.

Plates: Bearing 10,11 For partitions 16, 17, 53-57 Plumbing 102 Posts, wood, in basements 8 Q

Quality of materials: Aggregate 11,41 Brick 8,28,32 Cement 8,28,33 Concrete 11,41 Hollow masonry units 9, 28, 37, 38 Lime 8, 28 Lumber 14, 15, 28, 53, 55, 58 Mortar 8, 33 Miscellaneous 28 R

Rafters: Specifications 16, 50 Supported and tied 16, 60, 61 Rat proofing 70
INDEX 107

Recesses. See Chases. Page

Registers, fire stopping around 24, 99 Reinforced concrete dwellings 13, 42, 43 Reinforcement in monolithic construction, 12, 41, 42 Refiuirements; Limited to dwellings 6-9, 11, 13, 14, 17, 19 Minimum, for safe and economical construction 5-25, 26 Roofs: Anchorage for 7,60,61 Chimneys through 21, 81, 82, 83 Coverings. 79 Live loads upon... 7,30 Roof construction for attached garages 24, 101 Rubblestone foundation walls 7 S

Sand-lime brick. See Brick. Sheathing: Behind masonry veneer 14, 43, 44 For stucco dwellings 14,45 In frame construction 13,60-63

Sills 16,58,66,67 Smoke rapes:

I nstallation 22, 90 Intakes and thimbles 22,90

Soil, bearing capacity of 30 Sprinklers 93 Standard specifications: For fire tests - 91 Of -\merican Society for Testing Materials. 28 Of governmental agencies 29

Stresses: Beari ng for j oists - - 48 Increased for temporary loads 47 Timber 15 Structural clay tile. See Hollow masonry

units. Stucco on frame construction, requirements. 14,

44, 45 T

Termites 66-70 Timber:

Construction. See Frame dwellings and wood framing. Cost influenced by length 59,60

Lintels 9, 11, 12 Prohibited in masonry walls 9, 11 Protection from decay 8. 13, 14, 21, 52, 53, 55, 58 Quarter-sawed stock desirable - 59 Shrinkage and swelling 58,59 Weights of - 27 Working stresses 15

Page

Trade publications, value of 103 Trimmer arches 21,81 V

Veneered construction 13, 43 Vent flues, requirements for 20, 21 W

Walls: Anchors in 9, 10, 12, Arches and lintels in 9, Brick, solid 8, 9, Changes in thickness Concrete, monolithic 11-13, Corbeled, for chimney support Faced

Fire resistance 17, 24, 35, 38, 43, 79, Foundation

Height defined 5, HoUow, of brick Metal frame Of hollow masonry units 10, Party or division 17, 18, Parapet

Recesses or chases in 9, Reinforced concrete

Stability, lateral supports

9, 12, 16, 34, 36, 38, 43, Thickness 7, 8, 10, 12, 30, 31, 34, 36, 38, Venee^d Woodirame 13, Warm-air pipes: Covered in basements

Fire stopping around Weight of materials Wind pressure: On roofs On walls 34, 36, 38, Stresses may be increased 14, Wood framing: General requirements

Girders anchored and fastened

Joist sizes 13, 48, Joists anchored and supported

Joists doubled under partitions Rafter sizes Rafters supported and tied

Sills Wood joists: Anchors for Allowable lengths for given sizes Bearing in walls Separated from chimneys 21, 22, Separation in walls Working stresses. See Stresses.

16, 35

11, 12 34-37

9

41, 42

19, 80

10, 40

91, 92 30-32

10, 39

17, 64

11,38

78, 79

18, 79

11, 12

12, 41

7,8, 45,60

39, 43

13, 43 61-63

22,91

24, 93

27

60, 61

15, 47

14

16, 60

49, 59

16, 51

1650

16, 60

16, 51

1648

10, 16 83-87

18 O




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