American Standard

Building Code Requirements

For Masonry

U. S. Department of Commerce

National Bureau of Standards

Miscellaneous Publication 211

UNITED STATES DEPARTMENT OF COMMERCE • Sinclair Weeks, Secretary NATIONAL BUREAU OF STANDARDS • A. V. Astin, Director

American Standard Building Code

Requirements for Masonry

By

Sectional Committee on Building Code Requirements and Good Practice Recommendations for Masonry—A41

Under the Sponsorship of the National Bureau of Standards

Approved

September 28, 1953, by the American Standards Association

as American Standard A41. 1-1953

National Bureau of Standards Miscellaneous Publication 211

Issued July 15, 1954

(Supersedes Miscellaneous Publication 174)

For sale by the Superintendent of Documents, U. S. Government Printing Office Washington 25, D. C. - Price 20 cents
Foreword

This standard is a revision of an earlier edition (1944), and has been

approved by the American Standards Association as American Standard Building Code Requirements for Masonry, A41.1-1 9 53. It is a' complete code of minimum requirements for masonry construction

including definitions, requirements for materials, allowable stresses, and general requirements for all types of masonry except reinforced

masonry and thin veneers. This document, prepared by American:

Standards Association Sectional Committee A41 under the sponsorship

of the National Bureau of Standards, is one of a series of building code

standards prepared by various committees under the jurisdiction of j: the Construction Standards Board of the American Standards

Association.

A. V. Astin, Director. \

i|io

Jfii

ifla m
Sectional Committee

The personnel of the Sectional Committee on Building Code eqmrements and Good Practice Recommendations for Mlsonry

41, which developed this standard, is as follows:

ational Bureau of Standards, Sponsor D. E. Parsons, Chairman

J. W. McBurney, Secretary

Organization represented Representative merican Ceramic Society j. W Whit?kmore nencan Institute of Architects TheodIe I RVmo Coe

Ben H. Dyer

Merican Public Works Association, _ . _ _ Roy L

' Philips -nencan Society of Civil Engineers W. L. Dickey

E. A. DOCKSTADER

S. B. Barnes (Alternate) nerican Society for Testing Materials R. K Dato

(Alternate) K. F. Wendt

P. M. WoODWORTH

J. M. Hardesty (Alternate)

Wiated General Contractors of America, N.altaTM J Jeffress (Alternate)

/icklayers Masons and Plasterers Inter- A. J. Cleland mtional Lmon of America.

ilding Officials Conference of America Eugene M. Smith ildmg irades Employers Association of the Peter W Elleb ^ity of New Y ork.

e Finishing Lime Association of Ohio L. E. Johnson

e Protection Group E. W. Fowler

nnMl r, * , . . H. A. Sweet

SL. Q

erV1

-CeS Admmistration-Public C. W. Chamberlain feteFinance Agency

JW.V=

voting).

<$SS?M

tional Association of Real Estate Boards... 1* U^lson^ (Alteniate)

honal Bureau of Standards J. W. McBurney

tional Concrete Masonry Association R. E.' Copeland lona Crushed Stone Association A. T. Goldbeck lona Sand and Gravel Association Stanton Walker ponal blag Association pEED Hubbard

Tfi.^

an

+d r?^ Alexander Addeo lific Coast Building Officials Conference—. Hal Colling

^i?r?eniATClat\0U --. J- P- Thompson

ictural Clay Products Association H. C. Plummer mbers-at-Large A. H. Baker

Theodore Crane

Paul E. Jeffers (deceased)

Albyn Mackintosh

Walter C. Voss

Torgan Strong, Chairman, ASA Construction Standards Board, serves as

fficio member of the committee.

ITI
Contents

Page Foreword * Sectional Committee

Section I. General

1.1 Scope

1.2 Application of requirements

1.3 Dimensions

1.4 Alternate materials and constructions---

1.5 Tests

1.5.1 When required

1.5.2 Methods

1.5.3 Compressive stresses

1.6 Definitions

1.6.1 Abbreviations

1.6.2 Approved

1.6.3 Architectural terra cotta_ - 1.6.4 Ashlar facing

1.6.5 Ashlar masonry

1.6.6 Bonder (header)

1.6.7. Brick

1.6.8. Building

1.6.9. Building official 1.6.10. Concrete

1.6.11. Cross-sectional area

1.6.12. Grout (see Mortar)

1.6.13. Grouted masonry

1.6.14. Header (see Bonder)

1.6.15 Height of wall

1.6.16. Hollow masonry unit

1.6.17. Leaf (leaves), (see Wythe)

1.6.18. Masonry

1.6.18.1. Masonry of hollow units

1.6.18.2. Solid masonry

1.6.19. Mortar

1.6.20. Partition r 1.6.20.1. Nonbearing partition

1.6.21. Pier

1.6.22. Required

1.6.23. Rubble

1.6.23.1. Coursed rubble

1.6.23.2. Random rubble

1.6.23.3. Rough or ordinary rubble

1.6.24. Solid masonry unit

1.6.25. Story

1.6.26. Walls

1.6.26.1. Bearing wall ---

1.6.26.2. Cavity wall (core wall), (see Hollow wall;

.

1.6.26.3 Faced wall

1 6.26.4. Foundation wall

1.6.26.5. Hollow wall

1 6.26.5.1. Cavitv wall (core wall)

1.6.26.5.2. Masonry bonded hollow wall

1.6.26.6. Nonbearing wall

1.6.26.7. Parapet wall

1.6.26.8. Party wall

1.6.26.9. Veneered wall

1.6.27. Wythe (leaf) Section 2. Materials

2.1. Quality

2.1.1. Second-hand materials

2.2. Standards of quality

2.2.1. Building brick

2.2.1.1. Brick and solid clay or shale masonry units.

2.2.1.2. Sand-lime brick

2.2.1.3. Concrete brick

2.2.1.4. Grades

IV
Section 2. Materials—Continued 2> age

2.2.2. Structural clay tile and hollow clay or shale masonry units 5

2.2.2.1. Load-bearing wall tile ' ___ 5

2.2.2.2. Xonload-bearing tile 5

2.2.3. Concrete masonry units 5

2.2.3.1. Hollow load-bearing units 5

2.2.3.2. Hollow nonload-bearing units ,5 2.2.3.3. Solid load-bearing units _ 5

2.2.4. Stone 5

2.2.4.1. Cast stone "" 5

2.2.4.2. Natural stone ~__ ~~

'__ ~ 5

2.2.5. Architectural terra eotta 5

2.2.6. Glazed building units 5

2.2.7. Glass block 6

2.2.8. Gypsum tile and block 6

2.2.9. Cementitious materials 6

2.2. 10. Aggregate for mortar 6

2.2.11. Aggregate for concrete 6

2.2.12. Water 6

2.3. Plain concrete 6 ection 3. Mortar 6

3.1. Quality 6

3.2. Grout 6

3.3. Gypsum mortar 7

3.4. Types of mortar permitted ~ 7 lctton 4. Allowable Stresses 7

4.1. General 7

4.2. Allowable stresses 8

4.2.1. Higher stresses 8

4.2.2. Composite walls 9

4.2.3. Allowable stresses in plain concrete 9 action 5. Lateral Support 9

5.1. Ratio of height or length to thickness 9

5.2. Method of support 9

5.3. Piers 9 :ction 6. Thickness of Masonry 10

6.1. General 10

6.1.1. Change in thickness 10

6.1.1.1. Variation in thickness 10

6.1.1.2. Decrease in thickness 10

6.2. Thickness of bearing walls 10

6.2.1. Minimum thickness 10

6.2.2. Rubble stone walls "

_ ~

"

~_ 10

6.2.3. Exceptions 1q

6.2.3.1. Stiffened walls __~ 10

6.2.3.2. Top story walls 10

6.2.3.3. Walls of residence buildings 10

6.2.3.4. Penthouses and roof structures 10

6.2.3.5. Walls of plain concrete 1] 6.2.3.6. Hollow walls (cavity or masonry bonded) 1 6.2.3.7. Faced walls * 1 3.3. Thickness of non-bearing walls and partitions l: 6.3.1. Nonbearing walls l; 6.3.2. Nonbearing partitions i; 6.3.3. Gypsum tile and block 1 ).4. Foundation walls 1 6.4.1. Thickness l; 6.4.2. Exceptions 1 6.4.2.1. Reinforced masonry l:

„ 6.4.2.2. Allowable depth of 8-inch foundation walls 1! 6.4.2.3. Rubble stone 12

6.4.2.4. Plain concrete 12

6.4.2.5. Foundation walls supporting brick veneer or cavity walls_„ 12

.5. Parapet walls 12 ?tion 7. Bond 12

.1. Walls of solid masonry units 12

7.1.1. Bonding with bonders (headers) 12

7.1.2. Bonding with metal ties 12

1
Section 7. Bond—Continued

7.2. Masonry walls of hollow units

7.3. Stone walls

7.3.1. Ashlar masonry

7.3.2. Rubble stone masonry

7.4. Openings in walls of plain concrete

7.5. Faced walls

7.5.1. Bonding masonry facing

7.5.2. Bonding ashlar facing

7.6. Hollow walls (cavity and masonry bonded)

7.6.1. Cavity walls

7.6.2. Masonry-bonded hollow walls

7.7. Bonding of intersecting walls

7.7.1. Where bonded

7.7.2. Bonding bearing walls

7.7.3. Walls carried up separately

7.7.4. Bonding nonbearing walls Section 8. Grouted Masonry

8.1. Materials

8.2. Construction

Section 9. Veneers

9.1. Requirements

9.2. Load

Section 10. Glass Block

10.1. Where permitted

10.2. Size of panels

10.3. Reinforcement of exterior panels

10.3.1. Anchorage

10.3.2. Placing reinforcement

10.4. Mortar

10.5. Expansion joints

Section 11. Miscellaneous Masonry Requirements.

11.1. Anchoring of walls

11.1.1. Meeting or intersecting walls

11.1.2. Fastening joists or beams

11.1.3. Spacing

11.1.4. Anchoring structural members

11.2. Chases and recesses

11.2.1. Limitations

11.2.1.1. Exceptions for 8-inch walls

11.2.2. Recesses for stairways or elevators

11.3. Lintels and arches

11.3.1. Material

11.3.2. Stiffness

11.3.3. Design

11.4. Beams and joist supports _ 11.4.1. Beams

11.4.2. Joists

11.4.3. Support on wood

11.5. Corbelling

11.5.1. Maximum projection —

11.5.2. Corbelling chimneys

11.6. Cornices

11.7. Drainage of hollow walls

11.8. Use of existing walls

11.8.1. Permission required

11.8.2. Walls of insufficient thickness

11.9. Precautions during erection

11.9.1. Bracing to resist lateral loads

11.9.2. Wetting of brick

11.9.3. Protection against freezing

Appendix

References

VI
merican Standard Building Code Requirements

for Masonry

By

Sectional Committee on Building Code Requirements

nd Good Practice Recommendations for Masonry—A41

Under the Sponsorship of the National Bureau of Standards

This standard is a revision of an earlier edition (1944), and has been approved

y the American Standards Association as American Standard Building Code

Requirements for Masonry, A41. 1-1953. It is a complete code of minimum

equirements for masonry construction including definitions, requirements for

naterials, allowable stresses, and general requirements for all types of masonry

except reinforced masonry and thin veneers. This document, prepared by Ameri- an Standards Association Sectional Committee A41 under the sponsorship of the

ational Bureau of Standards, is one of a series of building code standards pre- oared by various committees under the jurisdiction of the Construction Standards

3oard of the American Standards Association. The basis of the requirements of his standard, together with examples of good practice, is discussed in an appendix.

.1. Scope. This standard covers requirements suitable for use in

uilding codes, applying to the design and construction of masonry in milding construction. It does not include requirements for reinforced

oncrete, reinforced gypsum concrete, or reinforced masonry, 1 nor equirements concerning fire protection.

.2. Application of Requirements. Masonry construction in any

uilding or other structure shall conform to these requirements.

.3. Dimensions. Unless the word "actual" is used, the dimensional

equirements for masonry given in this standard are nominal, and

pply to such dimensions as minimum thicknesses and heights of walls, 'he measured dimensions of the masonry may be less than the re- uired nominal dimensions by the thickness of one mortar joint, but

ot more than one-half inch, and by the amount of the dimensional

^lerance permitted by specifications applying to units used in the conduction. (Appendix 1.3.)

.4. Alternate Materials and Constructions. Masonry materials and

lethods of construction not specifically authorized by these requirelents may be permitted in accordance with the provisions of the

uilding code.

5. Tests.

1.5.1. When Required. Whenever there is insufficient evidence

lat any material or construction conforms to these requirements, or

lere is insufficient evidence to substantiate claims for alternate

See American Standard Building Code Requirements for Reinforced Concrete (ACI 318-51, ASA A89.1-

l|, and Ameiican Standard Building Code Requirements for Reinforced Gypsum Concrete, ASA A59.1-

•5. A proposed standard for reinforced masonry is under development in Sectional Committee A41.

Abstract

Section 1. General
materials or construction, the building official may require tests as proof of compliance to be made at the expense ol the applicant by an approved agency.

1.5.2. Methods. Tests of masonry materials shall be made in accordance with generally recognized standards. Strength tests of masonry constructions shall be made in accordance with the Tentative

Methods of Conducting Strength Tests of Panels for Building Construction, ASTM E 72-51 T. Duly authenticated tests by a competent person or laboratory may be accepted by the building official in lieu of tests under his own supervision. (See Appendix 2.) 1.5.3. Compressive Stresses. Allowable compressive stresses in alternate constructions shall not exceed one-fourth of the average

compressive strength of representative specimens of the proposed

construction as determined by responsible authorities.

1.6. Definitions. Unless otherwise expressly stated, the following

terms shall, for the purpose of this standard, have the meanings indi- cated in this section. Where terms are not defined in this section,

they shall have their ordinarily accepted meanings, or such as the

context may imply.

1.6.1. Abbreviations.

ACL American Concrete Institute, 18263 W. McNichols Rd.,

Detroit 19, Mich.

ASA. American Standards Association, Incorporated, 70 East

45th Street, New York 17, N. Y.

ASTM. American Society for Testing Materials, 1916 Race Street,

Philadelphia 3, Pa.

psi. Pounds per square inch.

1.6.2. Approved. Approved by the building official or other

authority having jurisdiction.

1.6.3. Architectural Terra Cotta. Plain or ornamental (molded

or extruded) hard-burned building units, usually larger in size than

brick, consisting of mixtures of plastic clays, fusible minerals, and

grog, and having a glazed or unglazed ceramic finish. 1.6.4. Ashlar Facing. Facing of a faced or veneered wall composed of solid rectangular units usually larger in size than brick,

having sawed, dressed, or squared beds, and mortar joints.

1.6.5. Ashlar Masonry. Masonry composed of rectangular units

usually larger in size than brick and properly bonded, having sawed,

dressed, or squared beds, and mortar joints.

1.6.6. Bonder (Header). A masonry unit which ties two or more wythes (leaves) of the wall together by overlapping, such as a header, j 1.6.7. Brick. A solid masonry unit having a shape approximately

a rectangular prism, usually not larger than 4 by 4 by 12 inches. A

brick may be made of burned clay or shale, of fire clay or mixtures; 3! thereof, of lime and sand, of cement and suitable aggregates, or of

' other approved materials.

1.6.8. Building. A structure enclosed within a roof and withini exterior walls or fire walls designed for the housing, shelter, enclosure

and support of individuals, animals or property of any kind.

1 .6.9. Building Official. The officer or other designated authority

charged with the administration and enforcement of the building code, or his duly authorized representative. jl^ 1.6.10. Concrete. A mixture of portland cement, aggregates andj,p

e water. (See 1.6.20 and 2.3.)
1.6.11. Cross-sectional Area. Net cross-sectional area of a masonry unit shall be taken as the gross cross-sectional area minus

the area of cores or cellular space. Gross cross-sectional area of scored units shall be determined to the outside of the scoring but the

cross-sectional area of the grooves shall not be deducted from the

gross cross-sectional area to obtain the net cross-sectional area

1.6.12. Grout (see Mortar).

1-6.13. Grouted Masonry. Grouted masonry is masonry in which

the interior joints are filled by pouring grout therein as the work

progresses.

1.6.14. Header (see Bonder).

1.6.15 Height of Wall. The vertical distance from the foundation wall or other immediate support of such wall, to the top of the

1.6.16 Hollow Masonry Unit. A masonry unit whose net cross- sectional area m any plane parallel to the bearing surface is less than

75 percent ot its gross cross-sectional area measured in the same plane

(bee Cross-sectional Area.)

1.6.17. Leaf (leaves). (See Wythe.)

L ^; 18. Masonry. A built-up construction or combination of building units of such materials as clay, shale, concrete, glass, gypsum

Dr stone, set in mortar; or plain concrete.

1.6.18.1. Masonry of Hollow Units. Masonry consisting wholly or m part of hollow masonry units laid contiguously in mortar.

1.6.18.2. Solid Masonry. Masonry consisting wholly of solid

nasonry units laid contiguously in mortar, or consisting of plain

concrete.

1.6.19. Mortar. A plastic mixture of cementitious materials, fine tggregates and water, used to bond masonry or other structural units

vlortar of pouring consistency is termed grout.

I 1.6.20. Partition.

1.6.20.1. Nonbearing Partition. An interior nonbearing wall ne story or less in height.

1.6.21. Pier. An isolated column of masonry. A bearing wall

Jot bonded at the sides into associated masonry shall be considered

pier when its horizontal dimension measured at right angles to the

fuckness does not exceed four times its thickness.

\ 1.6.22. Required. Means required by this standard.

\6.23. Rubble.

1.6.23.1. Coursed Eubble. Masonry composed of roughly

^laped stones fitting approximately on level beds, well bonded, and

'rought at vertical intervals to continuous level beds or courses.' 1.6.23.2. Random Rubble. Masonry composed of roughly

laped stones, well bonded and brought at irregular vertical intervals

j discontinuous but approximately level beds or courses.

1.6.23.3. Rough or Ordinary Rubble. Masonry composed of jmshaped or field stones laid without regularity of coursing,

i 1.6.24. Solid Masonry Unit. A masonry unit whose net crossi ctional area in every plane parallel to the bearing surface is 75 per-

! nt or more of its gross cross-sectional area measured in the same

'ane. (See Cross-sectional Area.)

i,1.6.25. Story. That portion of a building included between the

toper surface of any floor and the upper surface of the floor next above,

jlcept that the topmost story shall be that portion of a building in298033°—54 2 3
eluded between the upper surface of the topmost floor and the ceiling or roof above.

1.6.26. Walls.

1.6.26.1. Bearing Wall. A wall which supports any vertical

load in addition to its own weight.

1.6.26.2. Cavity Wall (Coke Wall). (See Hollow Wall.)

1.6.26.3. Faced Wall. A wall in which the masonry facing and

the backing are of different materials and are so bonded as to exert a common reaction under load.

1.6.26.4. Foundation Wall. A wall below the floor nearest grade serving as a support for a wall, pier, column, or other structural

part of a building.

1.6.26.5. Hollow Wall. A wall of masonry so arranged as to provide an air space within the wall between the inner and outer

parts (wythes) of the wall.

1.6.26.5.1. Cavity Wall (Core Wall). A wall built of masonry

units or of plain concrete, or a combination of these materials, so ar- ranged as to provide an air space within the wall (with or without

insulating material) , and in which the inner and outer wythes of the

wall are tied together with metal ties. 1.6.26.5.2. Masonry Bonded Hollow Wall. A hollow wall built - of masonry units in which the inner and outer wythes of the wall are { bonded together with masonry units, such as in the all-rolok and

rolok-bak walls.

1.6.26.6. Nonbearing Wall. A wall which supports no vertical

load other than its own weight.

1.6.26.7. Parapet Wall. That part of any wall entirely above

the roof.

1.6.26.8. Party Wall. A wall on an interior lot line used or adapted for joint service between two buildings;

1.6.26.9. Veneered Wall. A wall having a facing of masonry

or other material securely attached to the backing, but not so bonded

as to exert a common reaction under load.

1.6.27. Wythe (Leaf). Each continuous vertical section of a wall one masonry unit in thickness and tied to its adjacent vertical section or sections (front or back) by bonders (headers), metal ties or grout.

Section 2. Materials

(See Appendix 2) 2.1. Quality. Materials used in masonry shall be of good quality

conforming to generally accepted good practice. Except as may be otherwise provided herein, the standards 2 and requirements set forth in Section 2.2, Standards of Quality, shall be deemed to represent

generally accepted good practice in building construction. (See

; Section 1.5.2.) 2.1.1. Secondhand Materials. Secondhand materials shall nol be used in masonry unless such materials conform to these requirements and have been thoroughly cleaned. (See Appendix 2.1.1.)

2.2. Standards of Quality.

2.2.1. Building Brick. (See Appendix 2.2.1.)

2 Since national standards are revised at frequent intervals, references should be made to the latest edition in incorporating these standards in a local code.

4
2.2 1.1 Brick and Solid Clay or Shale Masonry Units. standard Specifications for Building Brick (Solid Masonry Units Made from Clay or Shale) ASTM C 62-50.

2.2 12. Sand-Lime Brick. American Standard Specifications

or Sand-Lime Building Brick (ASTM C 73-51; ASA A78 1-1952)

2.2.1.3 Concrete Brick American Standard Specifications

or Concrete Building Brick (ASTM C 55-52; ASA A75. 1-1953)

2.2 1.4. Grades. Clay, shale, or sand-lime brick subject to the

ction ol weather or soil, but not subject to frost action when permeated with water, shall be of Grade MW or Grade SW, and when subfeet to temperature below freezing while in contact with the soil shall |e ot Grade SW; concrete brick subject to the action of weather or

fjoil shall be of Grade A.

th»TM„~In 1oJ^m where brick conforming in physical properties to the requirements of this specification are not readilv obtainable, the use ol other brick should be permitted, if suitable evidence of strength and resistance to weathering is presented to the building official. nits

StrUctUTal Clay Tile and Hollow Clay or Shale Masonry

j,

1 2.2.2 1. Load-Bearing Wall Tile. American Standard Specilocations lor Structural Clay Load-Bearing Wall Tile (ASTM C 34-52

h 8^,^4 - 1 -1 .^^). Structural clay tile subject to the action of eather or soil shall be of Grade LBX, or, if used for load-bearing

jlurposes but not subject to the action of weather or soil, of Grade LB

^ Grade LBX of this specification.

2.2.2.2. Nonload-Bearing Tile. American Standard Specifi- l|Uions lor Structural Clay Nonload-Bearing Tile (ASTM C 56-52-

ISA A76.1-1953).

i 2.2.3. Concrete Masonry Units (See Appendix 2.2.3.) 2.2.3.1. Hollow Load-Bearing Units. American Standard

r) TMons for Hollow Load-Bearing Concrete Masonry Units iiSTM C 90-52; ASA A79. 1-1953), for hollow units in load-bearing

lasonry or subject to the action of weather or soil.

1 1

, 2.2.3.2. Hollow Nonload-Bearing Units. American Standpd Specifications for Hollow Nonload-Bearing Concrete Masonry

cuts (ASTM C 129-52; ASA A80.1-1953), for hollow units used in

: nload-bearmg masonry not subject to the action of weather or soil. 2.2.3.3. Solid Load-Bearing Units. American Standard Specii ations for Solid Load-Bearing Concrete Masonry Units (ASTM C

5-52; ASA A81. 1-1953). Solid units subject to the action of yatner or soil shall be Grade A.

2.2.4. Stone.

[j 2.2.4.1. Cast Stone. Specification for Cast Stone, ACI 704-44.

i

?- 2 - 4 - 2

; . Natural Stone. Stone used in masonry shall be sound,

f

; je Irom friable inclusions and have sufficient strength, durability,

instance to impact and abrasion for the proposed use. (See Adfljidix 2.2.4.2.)

J.2.5. Architectural Terra Cotta. Architectural terra cotta

S| 11 have a strong homogeneous body and shall conform to the app >able requirements of Sections 2.2.1.1 and 2.2.2. All units shall

bj^e the necessary anchor holes and shall be so formed as to engage

p perly with the supporting structure.

!

! .2.6. Glazed Building Units. Units shall conform to the app |able requirements of the specifications for hollow or solid clav

jponry units of Sections 2.2.1.1 and 2.2.2.

5
2 2 7 Glass Block. Block may be solid or hollow; mortar bearing

surfaces of the blocks shall be provided with a surface or a coating

material to afford adhesion between mortar and block.

2 2 8 Gypsum Tile and Block. Standard Specifications for Gypsum Partition Tile or Block, ASTM C 52-41.

2 2.9. Cementitious Materials.

Gypsum, (ASTM C 22-50; ASA A49. 1-1951).

Hydrated Lime for Masonry Purposes, ASTM C 207-49- Hydraulic Hydrated Lime for Structural Purposes, AblM I

141-42.

Quicklime for Structural Purposes, ASTM C 5-26.

Masonry Cement, ASTM C 91-52T. (See footnote 3 in Appendix 6.1)

Natural Cement, ASTM C 10-52T.

Portland Cement, ASTM C 150-52.

Air-Entraining Portland Cement, ASTM C 175-51 T. Portland Blast Furnace Cement, ASTM C 205-51 T.

2 2 10. Aggregate for Mortar. Standard Specifications lor Aggregate for Masonry Mortar, ASTM C 144-52T

2 2 11 Aggregate for Concrete. Standard Specifications tor Concrete Aggregates, ASTM C 33-52T or Standard Specifications foi Lightweight Aggregates for Concrete, ASTM C 130-42; other aggre- gates may be approved which have been shown by test or experience

to be satisfactory for the intended purpose.

2 2 12 Water. Water shall be clean, and free from injurious

amounts of oils, acids, alkalis, organic materials, or other deleterious

substances.

2.3 Plain Concrete . 2 3 1 The requirements for concrete m Building Code Kequire

ments for Reinforced Concrete (ACI 318-51; ASA A89. 1-1951) shal be deemed to describe the generally accepted good practice m plan concrete construction.

2.3.2. Concrete exposed to freezing temperature shall have ai effective mixing water content of not more than 6 gal per sack o cement (53 lb per 100 lb of cement). Concrete exposed to the groum

or the weather, except in arid regions, shall have an effective mixing k

water content of not more than 7% gal per sack of cement (66 lb pe 100 lb of cement). These requirements may be waived it adequate

tests or experience show that concrete with a higher water conten f

, gives satisfactory durability and protection of reinforcement uncle the prevailing conditions. Cellular concrete or concrete made witJ light weight aggregate and used under conditions not subject to grouni or weather exposure, shall have a compressive strength of at least 60

psi at the age of 28 days, and that for floor or roof fill, a strength of a least 150 psi. The strength of the concrete for all conditions shall t> such that the allowable stresses determined as in Section 4.2.3 are no< exceeded. (See Appendix 2.3.2.)

' ist Section 3. Mortar

3 1 Quality. Mortar shall conform to the requirements of AST^

Tentative Specifications for Mortar for Unit Masonry, ASTM Desi£

nation C 270-52T. (See Appendix 3.1 including footnote 5.) 3 2. Grout. Grout shall be Type A-l, Type A-2, or Type B mort*

as defined in ASTM C 270-52T to which is added water to produc

6
mortar Tvn. HTM* F^vft segregation of constituents of the mortar Type A-l grout shall be used with Type A-l mortar - either

Type

Type

A-2

A-l or

or Type

Type

2-A

B grout

grout shall be used with Type A-2; TvpeTl shall be used with Type B mortar

' h.3. Gypsum Mortar. Gypsum mortar shall be composed by weight

4greg

eatea gJPSUm *"* n0t m°re than three Parts ^

- Types of Mortar Permitted. Masonry shall be laid in mortar the types specified in table 1. (See Appendix 3.4.)

Table 1.

8.4

Kind of masonry foundations: Footings Walls of solid units ~__ Walls of hollow units Hollow walls lasonry other than foundation masonry7 Piers of solid masonry

Piers of hollow units ~ Walls of solid masonry

Walls of solid masonry, other" than parapet"wails" or rubble stone walls, not less than 12 inches thick nor more than 35 feet in height, supported laterally at intervals not exceeding 12 times the wall thickness. Walls of ho ow units; load-bearing or exterior, and hollow walls 12 in. or more in thickness. Hollow walls, less than 12 in. in thickness where as- sumed design wind pressure: a (a) exceeds 20 pounds per sq ft (b) does not exceed 20 pounds per sq ft I Glass block masonry

None-bearing partitions of fire-proofing "composed" of

structural clay tile or concrete masonry units Gypsum partition tile or block

Fire brick Linings of existing masonry, either above or below grade

Masonry other than above

Types of mortar permitted

A-l, or A-2

A-l, A-2 or B

A-l or A-2

A-l or A-2

A-l, A-2 or B

A-l or A-2

A-l, A-2, B or C

A-l, A-2, B, C, or D

A-l, A-2 or B

A-l or A-2

A-l, A-2 or B

A-l, A-2 or B

A-l, A-2, B, C, or gypsum. Gypsum

Refractory air setting mortar A-l or A-2

A-l, A-2 or B

&^ZS5jfiSS3L ffettSffi8

^°0de K^*TM ** Minimum

Section 4. Allowable Stresses

. General. In determining the stresses in the masonry, the effects

all loads and conditions of loading and the influence of all forces ectmg the design and strength of the several parts shall be taken

o account. Stresses shall be calculated on actual rather than tmnal dimensions. Masonry construction shall be so designed and istructed that the allowable stresses prescribed herein are not

•eeded.
4 2 Allowable Stresses. Except as permitted in other sections of this standard, the compressive stresses in masonry shall not exceed

the values given in table 2. Table 2. Allowable compressive stresses in unit masonry

(See Appendix 4.2.)

Construction; grade of unit

Solid masonrv of brick and other solid units

of clay or shale; sand-lime or concrete

brick: 8,000 pins, psi

4,500 to 8.000. psi

2,500 to 4,500, psi

1,500 to 2,500, psi

Allowable compressive stresses gross cross- sectional area (except as noted)

Grouted a solid masonry of brick and other

solid units of clay or shale; sand-lime

or concrete brick: 4.500 plus, psi

2,500 to 4,500, psi

1,500 to 2,500, psi

Type

A-l

mortar

psi 400

250

175

125

Type

A-2

mortar

Solid masonry of solid concrete masonry

units: Grade A

Grade B

Masonry of hollow units

Piers of hollow units, cellular spaces filled, as in Sec. 5.3 Hollow walls (cavity or masonry bonded) . b Solid units: Grade A or 2,500, psi plus

Grade B or 1,500 to 2,500, psi__

Hollow units Stone ashlar masonry:

Granite

Limestone or marble

Sandstone or cast stone Rubble stone, coursed, rough or random.

350

275 225

175 125

85

105

psi 350

225

160

115

275

215

175

160 115

Type B

mortar Type C

mortar

75

95

140 130 110

100 90 80

70 60 55

800 720 640

500 450 400

400 360 320

140 120 100

psi 300

200

140

100

200

155

125

140 100

70

90

psi 200

150

11075

Type D

mortar

10075

1 1 iK

psi100

100 • 75

5C

% (

i

j m

500 325

250

80

ft

25 percent. 42 1 Hiqher Stresses. Higher stresses than herein specif

may be used, but only if it is clearly established to the satisfactic of the building official, by test, or other approved evidence th material of a higher grade or a superior workmanship than is genera

provided in accepted practice will be employed under approy

inspection. The use of higher stresses, however, shall not be alio until a statement giving the reasons for such permission togetn

8
with the facts and circumstances on which it is based, has been placed on file and made a part of the official record of the permit. (See Appendix 4.2.1 for effect of workmanship.)

4.2 2. Composite Walls. In composite walls or other structural

members composed of different kinds or grades of units or mortars,

the maximum stress shall not exceed the allowable stress for the

weakest of the combinations of units and mortars of which the member

is composed. (See Appendix 4.2.2.)

4.2.3. Allowable Stresses in Plain Concrete. The allowable

stresses shall not exceed 25 percent for compression, and 3 percent

for tension in extreme fibre in flexure, of the compressive strength

of the concrete. When the ratio of height to thickness of structural

members of plain concrete exceeds 10, the percentage for compressive

stress shall be reduced proportionately to 18 percent for a ratio of height to thickness of 20. For hollow (cavity) walls of plain con- crete, the allowable stress shall not exceed 20 percent of the compressive strength of the concrete based upon the gross cross-sectional

] area of wall minus area of cavity. (See Appendix 4.2.)

Section 5. Lateral Support

5.1. Ratio of Height or Length to Thickness. The ratio of unsupported height to nominal thickness or the ratio of unsupported

length to nominal thickness (one or the other but not necessarily

both) for solid masonry walls or bearing partitions of buildings shall aot exceed 20 if of plain concrete or of solid masonry units if laid in Type A-l, A-2, B or C mortar, nor 12 if laid in Type D mortar; and,

Regardless of the type of permitted mortar used, shall not exceed 18

"or walls of hollow masonry units or hollow walls. In computing the

latio for cavity walls, the value foi thickness shall be the sum of the

lominal thicknesses of the inner and outer wythes. In walls com-

, )osed of different kinds or classes of units or mortars, the ratio of

• leight or length to thickness shall not exceed that allowed for the

| veakest of the combination of units and mortars of which the member

s composed. See Section 9.2 for veneers. For completed cantilever

rails of masonry the precautions of Section 11.9.1 shall be followed.

' See Appendix 5.1.)

.2. Method of Support. Lateral support may be obtained by cross

! rails, piers, or buttresses, when the limiting distance is measured

I orizon tally, or by floors and roofs when the limiting distance is leasured vertically. Sufficient bonding or anchorage shall be pro- vided between the walls and the supports to resist the assumed wind

r other horizontal force, acting either inward or outward. Piers, uttresses and cross walls relied upon for lateral support shall have

\ifficient strength and stability to transfer the horizontal force,

cting in either direction to adjacent structural members or to the

round. When walls are dependent upon floors or roofs for their

teral support, provision shall be made in the building to transfer ae lateral forces to the ground.

3. Piers. The unsupported height of piers shall not exceed 10 mes their least dimension provided that when structural clay tile r hollow concrete units are used for isolated piers to support beams

r girders, their unsupported height shall not exceed 4 times their

iast dimension unless the cellular spaces are filled solidly with

imcrete or either type A-l or A-2 mortar.

9
Section 6. Thickness of Masonry

(See Appendix 6)

6.1. General. The thickness of masonry walls shall conform to the

requirements of this Section and of Section 5, provided that the

allowable stresses in Section 4.1 and 4.3 shall not be exceeded.

6.1.1. Change in Thickness.

6.1.1.1. Variation in Thickness. Except for window-paneled

backs, and permissible chases and recesses, walls shall not vary in thickness between their lateral supports. When a change in thickness, due to minimum thickness requirements, occurs between floor

levels, the greater thickness shall be carried up to the higher floor

level.6.1.1.2. Decrease in Thickness. Where walls of masonry of hollow units or masonry bonded hollow walls are decreased in thickness a course or couises of solid masonry shall be interposed between the

wall below and the thinner wall above, or special units or construction

shall be used that will adequately transmit the loads from the shells above to those below.

6.2. Thickness of Bearing Walls.

6.2.1. Minimum Thickness. The thickness of masonry bearing

walls shall be at least 12 inches for the uppermost 35 feet of their height, and shall be increased 4 inches for each successive 35 feet or fraction thereof measured downward from the top of the wall, except

as otherwise permitted in Section 6.2.3, Exceptions.

6.2.2. Rubble Stone Walls. Rough or random or coursed rubble stone walls shall be 4 inches thicker than is required by Section 6.2.1 but in no case less than 16 inches thick. The exceptions of Section

6.2.3 shall not apply to rubble stone walls.

6.2.3. Exceptions. . 6.2.3.1. Stiffened Walls. Where solid masonry bearing walls are stiffened at distances not greater than 12 feet apart by masonry b cross walls or by reinforced concrete floors, they may be of 12-mch

p thickness for the uppermost 70 feet, measured downward from the

top of the wall, and shall be increased 4 inches in thickness for each

successive 70 feet or fraction thereof. . 6.2.3.2. Top Story Walls. The top story bearing wall ol a building not exceeding 35 feet in height may be of 8-inch thickness

provided it is not over 12 feet in height and the roof construction lm- j parts no lateral thrust to the walls.

6.2.3.3. Walls of Residence Buildings. In residence build- ; ings not more than 3 stories in height, walls other than coursed or , rough or random rubble stone walls, may be of 8-inch thickness when ;, not over 35 feet in height and the roof is designed to impart no hori- zontal thrust. Such walls in 1-story residence buildings, and 1-story

private garages, mav be of 6-inch thickness when not over 9 feet m

height, except that the height to the peak of a gable may be 15 feet, 6.2.3.4. Penthouses and Roof Structures. Masonry walls above roof level, 12 feet or less in height, enclosing stairways, machm- , ery rooms, shafts, or penthouses, may be of 8-inch thickness and may

be considered as neither increasing the height nor requiring any in- crease in the thickness of the wall below.

Id

10
6.2.3.5 Walls of Plain Concrete. Plain concrete walls may be 2 inches less m thickness than required by Section 6.2, but not less :nan 8 inches, except 6-mch walls as permitted by Section 6 2 3 3 bee Section 7.4.)

' 6.2 .3.6 Hollow Walls (Cavity or Masonry Bonded) Hol- ow walls sha 1 not exceed 35 feet in height except that 10-inch cavity

vails shall not exceed 25 feet in height above the support of such walk Lhe facing and backing of cavity walls shall each have a thickness of

it least 4 niches and the cavity shall be not less than 2 inches (actual)

lor more than 3 inches m width. n

6 - 2 ' 3

'J; F^

Cf° Wf

LLS - Neither the height of faced (composite)

rails nor the distance between lateral supports shall exceed that pre- cnbed for masonry of either of the types forming the facing or the

'acking. &

3. Thickness ef Nonbearing Walls and Partitions.

6.3 1. Nonbearing Walls. Nonbearing exterior masonrv walls iay be 4 inches less in thickness than required for bearing walls, but

tie tnickriess shall be not less than 8 inches except where 6-inch walls

re specifically permitted.

6.3.2. Nonbearing Partitions. The distance between lateral ipports of nonbearing partitions of masonrv shall not exceed 36 mes the actual thickness of the partition including plaster See

ection 5.2. (See Appendix 6.3.2.)

6.3.3. Gypsum Tile and Block. Gypsum partition tile or block

lall not be used m bearing walls, or where subject to continuous

ampness. Gypsum partition tile shall not be used for partitions to

^ceive portland cement plaster, ceramic tile, marble or structural

ass wainscots unless self-furring metal lath is placed over the gypsum

4. Foundation Walls. (See Appendix 6.4.)

! 6.4.1. Thickness. Foundation walls shall be of sufficient strength

id thickness to resist lateral pressures from adjacent earth and

&

to pport their vertical loads without exceeding the allowable stresses ^undation walls or their footings shall extend below the level of

)st action and shall be not less in thickness than the walls immediely above them except as provided in Section 6.4.2.5. Foundation

ills shall be at least 12 inches thick except as noted in Section 6 4 2

^ceptions. (See Appendix 6.4.1.)

6.4.2. Exceptions.

6.4.2.1. Reinforced Masonry. Foundation walls of masonrv

its supported laterally at vertical intervals not exceeding 12 feet ly be 8 inches thick if reinforced by means of vertical %-inch diamjv deformed reinforcing bars (or their equivalent) spaced not more

an 12 inches apart and not less than 3K inches from the pressure side

the wall; or ^-inch diameter deformed reinforcing bars (or their

ivalent) spaced not more than 24 inches apart and not less than

nches from the pressure side of the wall. Reinforcing bars shall end from footing to top of foundation wall. Bars shall be lapped

least 30 diameters at splices. The space between each bar and

adjacent enclosing masonry surfaces shall be solidly filled with

oe A-l grout or mortar. (See Appendix 6.4.2.1.) 6.4.2.2. Allowable Depth of 8-Inch Foundation Walls.

id foundation walls of solid masonry units or of coursed stone that

298033°—54 3 H
do not extend more than 5 feet below the adjacent finished ground

level may be 8 inches in thickness; cavity walls and walls of hollow

units that do not extend more than 4 feet below the adjacent finished

ground level, may be 10 inches and 8 inches, respectively, m thickness.

Those depths may be increased to a maximum of 7 feet with the

approval of the building official when he is satisfied that soil conditions

warrant such increase. The combined height of an 8-inch foundation

wall and the wall supported shall not exceed the height permitted lor 8-inch walls. (See Appendix 6.4.1.) . _

6.4.2.3. Rubble Stone. Foundation walls ol rubble stone shall be at least 16 inches thick. Rough or random rubble shall not be

used as foundations for walls exceeding 35 feet in height.

6 4.2.4. Plain Concrete. Foundation walls of cast-m-place concrete shall be at least 8 inches thick; provided that when the basement floor does not exceed 4 feet below average grade level, such walls may be 6 inches thick.

6 4.2.5. Foundation Walls Supporting Brick Veneer or Cavity Walls. Foundation walls of 8-inch thickness and conforming

to the provisions of this section may be used as foundations for dwell- ings with walls of brick veneer on frame walls, or with 10-mch cavity

walls - provided that the dwelling is not more than 1% stories m heightI

and the total height of the wall, including the gable, is not more than

20 feet Foundation walls of 8-inch thickness supporting brick veneei or cavity walls shall be corbelled with solid units to provide a bearing . the full thickness of the wall above unless adequate bearing is providec

by a concrete floor slab. The total projection shall not exceed

|

inches with individual corbels projecting not more than /3< the deptl

(height) of the unit. The top corbel course shall be not higher thai

the bottom of floor joists and shall be a full header course of headers

at least 6 inches in length. _ 6 5 Parapet Walls. Unless reinforced to withstand salely the eartn- quake and the wind loads to which they may be subjected, parape - walls shall be at least 8 inches thick and their height shall not exceed

three times their thickness. (See Appendix 6.5.)

Section 7. Bond

7.1. Walls of Solid Masonry Units. Solid masonry bearing an< nonbearing walls shall be bonded in accordance with Section 7.1.1 Bonding with Bonders or Section 7.1.2, Bonding with Metal Ties

(For grouted masonry walls, see Section 8.) - f

7 1 1 Bonding with Bonders (Headers) . The facing and back

ing snail be bonded so that not less than 4 percent of the wall surfac

of each face is composed of bonders (headers) extending not less tm\

4 inches into the backing. The distance between adjacent lui length headers shaU not exceed 24 inches either vertically or hor

zontally. In walls in which a single bonder does not extend throng ! the wall, bonders from the opposite sides shall overlap at least inches, or bonders from opposite sides shall be covered with anoth(

bonder course overlapping the bonder below at least 4 inches.

7.1.2. Bonding with Metal Ties. The facing and backing sha

be bonded with corrosion-resistant metal ties conforming to th requirements of Section 7.6 for cavity walls. There shall be or t; metal tie for not more than each 4% square feet of wall area. Ik..%\

12
in alternate courses shall be staggered, the maximum vertical distance

between ties shall not exceed 18 inches, and the maximum horizontal

distance shall not exceed 36 inches. (See Appendix 7.1.2 for figure.)

Walls so bonded shall conform to the allowable stress, lateral support,

i thickness (excluding cavity), height and mortar requirements for cavity walls.

7.2. Masonry Walls of Hollow Units. Where two or more hollow

units are used to make up the thickness of a wall, the stretcher courses

shall be bonded at vertical intervals not exceeding 34 inches by lapping

at least 4 inches over the unit below, or by lapping at vertical intervals

N not exceeding 17 inches with units which are at least 50 percent

greater in thickness than the units below; (see Appendix 7.2) or by

bonding with corrosion-resistant metal ties conforming to the requireJ ments of Section 7.6.1. There shall be one metal tie for not more than

each 4% square feet of wall area. Ties in alternate courses shall be

staggered, the maximum vertical distance between ties shall not exceed

| 18 inches, and the maximum horizontal distance shall not exceed 36

i: inches. (See Appendix 7.1.2 for figure.) Walls bonded with metal

f

ties shall conform to the requirements for allowable stress, lateral

i support, thickness (excluding cavity), height and mortar for cavity

i -walls. Hollow masonry units shall have full mortar coverage of the

ends and edges of the face shells in both the horizontal and vertical

joints. (See Appendix 4.2.1.)

I 7.3. Stone Walls.

7.3.1 Ashlar Masonry. In ashlar masonry, bond stones unii formly distributed shall be provided to the extent of not less than 10

[.percent of the area of exposed faces.

I 7.3.2. Rubble Stone Masonry. Rubble stone masonry 24 inches

I: or less in thickness shall have bond stones with a maximum spacing of

1,3 feet vertically and 3 feet horizontally, and if the masonry is of Lgreater thickness than 24 inches, shall have 1 bond stone for each 6

1 square feet of wall surface on both sides. If.4. Openings in Walls of Plain Concrete. Reinforcement symI TLetrically disposed in the thickness of the wall shall be placed not less

I ;han 1 inch above and 2 inches below openings and extend not less

I ;han 24 inches each side of such openings or be of equivalent developed

I ength with hooks. The minimum reinforcement both above and

I )elow openings shall consist of the equivalent of one %-inch round bar

Tor each 6 inches in wall thickness.

|

.5. Faced Walls.

ili 7.5.1. Bonding Masonry Facing. The actual (not nominal)

1 hickness of materials used for facing shall be not less than 2 inches and

J.n no case less than % the height of the unit. Masonry facing shall

>e bonded to the backing as prescribed in Section 7.1, Walls of Solid

/.lasonry Units.

7.5.2. Bonding Ashlar Facing. The percentage of bond stones

for ashlar masonry shall be computed from the exposed face area of

She wall. At least 10 percent of the face area shall consist of bond

itones which extend 4 inches or more into the backing wall and are miformly distributed. Every bonding stone, and, except when

lternate courses are full bond courses, every stone not a bond stone,

1-iall be securely anchored to the backing with substantial corrosion-

-sistant metal anchors with a cross-section of not less than %6-inch by

13
1 inch or its equivalent in cross-sectional area. There shall be at least

1 anchor to each stone and not less than 2 anchors for each stone more

than 2 feet in length and 3 square feet in face area; facing stones of greater size shall have at least 1 anchor to each 4 square feet of the

face area of the unit as applied but not less than two anchors.

7.6. Hollow Walls (Cavity and Masonry Bonded).

7.6.1. Cavity Walls. The facing and backing of cavity walls

shall be bonded with %6-inch diameter steel rods or metal ties of equivalent stiffness embedded in the horizontal joints. There shall be one metal tie for not more than each 4% square feet of wall area. Ties in alternate courses shall be staggered as indicated in Section

7.1.2 (see Appendix 7.1.2. for figure), the maximum vertical distance

between ties shall not exceed 18 inches, and the maximum horizontal

distance shall not exceed 36 inches. Rods bent to rectangular shape

shall be used with hollow masonry units laid with the cells vertical;

in other walls the ends of ties shall be bent to 90-degree angles to provide hooks not less than 2 inches long. Additional bonding ties shall be provided at all openings, spaced not more than 3 feet apart

around the perimeter and within 12 inches of the opening. Ties shall be of corrosion-resistant metal, or shall be coated with a corrosionresistant metal, or other approved protective coating.

7.6.2. Masonry- bonded Hollow Walls. Masonry bonded hol- low walls shall be bonded as required in Section 7.1.1, Bonding with

Bonders (Headers).

7.7. Bonding of Intersecting Walls.

7.7.1 . Where Bonded. Masonry walls shall be securely anchored

or bonded at points where they intersect and where they abut or.fi adjoin the frame of a skeleton frame building. (See Section 11.1 forfp

anchoring to floors.) 7.7.2. Bonding Bearing Walls. When two bearing walls meet) jo or intersect and the courses are built up together, the intersections

shall be bonded by laying in a true bond at least 50 percent of the

units at the intersection.

7.7.3. Walls Carried Up Separately. When the courses of meeting or intersecting bearing walls are carried up separately, the

intersecting walls shall be regularly toothed or blocked with 8-inch

maximum offsets and the joints provided with metal anchors having!!

a minimum section of ){ inch by 1% inches with ends bent up at least

1 11 2 inches, or with cross pins to form anchorage. Such anchors shall be

at least 2 feet long and the maximum spacing shall be 4 feet. 7.7.4. Bonding Nonbearing Walls. Meeting or intersecting

nonbearing walls shall be bonded or anchored to each other in an approved manner. SECTION 8. GROUTED MASONRY m

e

erti 8.1. Materials. Materials used in grouted masonry shall conform to the requirements of Section 2, Materials, provided that masonry lr units in either the facing or backing, but not necessaiily both, at the^j

time of laying, shall absorb in 24 hours of cold immersion an amount olj water weighing at least five percent of the dry weight of the unit.

8.2. Construction. All masonry units in the outer wythes shall be

laid with full head and bed joints of Type A-l or A-2 mortar and al

1

14
nterior joints shall be filled with grout. Masonry units in the interior

ivythes shall be placed or floated in grout poured between the two outer

vythes. One of the outer wythes may be carried up not more than

hree courses before grouting but the other shall be carried up not

iiore than one course above the grout. Each pour of grout shall be

stopped at least 1% inches below the top and properly stirred. The

grouted longitudinal vertical joints shall be not less than three-fourths

nch wide. Bonders shall not be used.

SECTION 9. VENEERS

ij9.1. Requirements. Installation of veneers shall be in conformance

with generally accepted good practice.3 1.2. Load. Veneers shall not be considered as part of the wall in Computing the strength of bearing walls nor shall they be considered

1 part of the required thickness of walls.

i SECTION 10. GLASS BLOCK

L0.1. Where Permitted. Masonry of glass blocks may be used in onload-bearing exterior or interior walls and in openings which might

otherwise be filled with windows, eithei isolated or in continuous bands,

provided the glass block panels have a thickness of not less than 3%

inches at the mortar joint and the mortared surfaces of the blocks are

satisfactorily treated for mortar bonding.

10.2. Size of Panels. Glass block panels for exterior walls shall not

exceed 144 square feet of unsupported wall surface nor 25 feet in

ength nor 20 feet in height between supports. For interior walls,

idass block panels shall not exceed 250 square feet of unsupported area

aor 25 feet in one direction between supports.

0.3. Reinforcement of Exterior Panels.

10.3.1. Anchorage. Exterior glass block panels shall be held in

)lace in the wall opening to resist both external and internal pressures

jlue to wind. Panels shall be set in recesses at the jambs and, for Panels exceeding 10 feet in horizontal dimension between supports, at

J ;he head as well, so as to provide a bearing surface at least one inch

'vide along the panel edges; except that when approved by the building

official for panels exceeding neither 100 square feet in area nor 10 feet

In either horizontal or vertical dimension, and situated 4 stories or less,

( md less than 52 feet above grade level, anchorage may be provided by

neans of noncorrodible perforated metal strips. 10.3.2. Placing Reinforcement. Glass block panels shall have

reinforcement in the horizontal mortar joints, extending from end to end of mortar joints but not across expansion joints, with any unavoidable joints spliced by lapping the reinforcement not less than 6 inches.

|rhe reinforcement shall be spaced not more than two feet apart

vertically. In addition reinforcements shall be placed in the joint

Immediately below and above any openings within a panel. The

•einforcement shall consist of two parallel longitudinal galvanized

Iteel wires, No. 9 gauge or larger, spaced 2 inches apart, and having

velded thereto No. 14 or heavier gauge cross wires at intervals not

Exceeding 8 inches, or the equivalent approved by the building official.

I

s A proposed standard for the installation of veneers is under preparation, and will be submitted to

, Sectional Committee A41 for consideration as a separate standard.

15
10.4. Mortar. Glass block shall be laid in Type A-l, A-2, or E

mortar. Both vertical and horizontal mortar joints shall be at least y4 and not more than % inch thick and shall be completely filled. 10.5. Expansion Joints. Ever}r exterior glass block panel shall be

provided with expansion joints at the sides and top. Expansion

joints shall be entirely free of mortar, and shall be filled with resilient material.

Section 11. Miscellaneous Masonry Requirements

11.1. Anchoring of Walls.

11.1.1. Meeting or Intersecting Walls. Masonry walls that

meet or intersect floors or columns shall be securely bonded or anchored

if these are depended upon for lateral support of the walls. (See

Section 7.7, Bonding of Intersecting Waifs.)

11.1.2. Fastening Joists or Beams. The ends of floor joists or beams bearing on masonry walls shall be securely fastened to the i walls in an approved manner. (See Appendix 11.1.2.)

11.1.3. Spacing. When lateral support for walls is to be provided

by anchorage to floor or roof joists which are parallel to the walls,

the anchors shall be spaced at intervals not exceeding 6 feet and shall engage not less than three joists; these joists shall be bridged solidly at the anchors. (See Appendix 11.1.3.)

11.1.4. Anchoring Structural Members. Structural members in- cluding roof members, framing into or supported by walls or piers shall be adequately anchored. (See Appendix 11.1.4.)

11.2. Chases and Recesses.

11.2.1. Limitations. Except as provided in Section 11.2.1.1,

chases and recesses in masonry walls shall not be deeper than % the

[ wall thickness nor longer than 4 feet horizontally or in horizontal

projection, and shall have at least 8 inches of masonry in back of the , chases and recesses and between adjacent chases or recesses and the

jambs of openings. Chases and recesses shall not be cut in walls of I hollow masonry units or in hollow walls, but when permitted may

be built in. There shall be no chases or recesses within the required area of a pier. The aggregate area of recesses and chases in any

J, wall shall not exceed % of the whole area of the face of the wall in I any story.

11.2.1.1. Exceptions for 8-Inch Walls. In residence buildings , not over 2 stories in height, vertical chases not more than 4 inches

[ deep and not more than 4 square feet of wall area may be built in , 8-inch walls, except that recesses below windows may extend from f

floor to sill and be the width of the opening above. Masonry directly ; above chases or recesses wider than 12 inches shall be supported onfl' lintels. 11.2.2. Recesses for Stairways or Elevators. Recesses for stair-

ways or elevators may be left in walls, but in no case shall the walls I at such points be reduced to less than 12 inches unless reinforced by

'

additional piers, or b}~ columns or girders of steel, reinforced masonry, h or concrete, securely anchored to the walls on each side of such recesses. Recesses for alcoves and similar purposes shall have not less than 8 j. inches of material at the back. Such recesses shall be not more than

t 8 feet in width and shall be arched over or spanned with lintels.

16

1 1

1
11.3. Lintels and Arches.

11 .3.1 . Material. The masonry above openings shall be supported

by arches or lintels of metal or reinforced masonry which shall bear on the wall at each end for not Jess than 4 inches. Stone or other

i nonreinforced masonry lintels shall not be used unless supplemented on the inside of the wall with iron or steel lintels or with suitable

masonry arches or reinforced masonry lintels carrying the masonry

i backing.

11.3.2. Stiffness. Steel or reinforced masonry lintels shall be of

sufficient stiffness to carry the superimposed load without deflection

of more than %M of the clear span.

11.3.3. Design. Masonry arches shall be designed in accordance

with good engineering practice.

hiA. Beams and Joist Supports.

11.4.1. Beams. Beams, girders, or other concentrated loads supported by a wall or pier, shall have bearing at least 3 inches in actual

, length upon solid masonry not less than 4 inches in depth or on a

; metal bearing plate of adequate design and dimensions, or other proVision shall be made to distribute safely the loads on the wall or pier.

I 11.4.2. Joists. Joists shall have bearing at least 3 inches in actual

-length upon solid masonry at least 2% inches in depth, or other provision shall be made to distribute safely the loads on the wall or pier. 11.4.3. Support on Wood. Unless specifically approved by the

building official, no masonry shall be supported on wood girders or pther form of wood construction.

11.5. Corbelling.

11.5.1. Maximum Projection. Except for chimneys, the maxiiium corbelled horizontal projection beyond the face of the wall shall

->e not more than % the wall thickness and the maximum projection

taf one unit shall neither exceed % the depth of the unit nor % its width

! it right angles to the face which is offset. 11.5.2. Corbelling Chimneys. No chimney shall be corbelled

, 'rom a wall more than 6 inches nor shall a chimney be corbelled from

-i wall which is less than 12 inches in thickness, unless it projects

equally on each side of the wall, provided that in the second story of ':wo-story dwellings, corbelling of chimneys on the exterior of the

Enclosing walls may equal the wall thickness. In every case the

'orbelling shall not exceed 1 inch projection for each course of brick

Projected.

11.6. Cornices. The centers of gravity of stone cornices shall be

Cnside of the outer wall face. Terra cotta cornices and metal cornices

[mall be structurally supported.

jl 1.7. Drainage of Hollow Walls. In cavity walls the cavity shall be

! cept clear of mortar droppings during construction. Approved

flashings shall be installed in hollow walls and adequate drainage

.brovided to keep dampness away from the backing. (See Appendix

[.1.7.) 1.8. Use of Existing Walls.

: 11.8.1. Permission Required. An existing masonry wall may

he used in the alteration or extension of a building provided that

• i rider the new conditions it meets the requirements of this standard

imd is structurally sound or can be made so by reasonable repairs.

17
No existing wall shall be used for the alteration or extension of building, or increased in height without specific written permissio

from the building official. 11.8.2. Walls of Insufficient Thickness. Existing masonr

wails which are structurally sound but which are of insufficient thick' ness when increased in height shall be strengthened by an additio

of the same material not less than 8 inches in thickness laid in Typ

A-l mortar. The foundations and lateral support shall be equivf

lent to those elsewhere required for newly constructed walls undf

similar conditions. All reinforcing linings shall be thoroughly bonde

into existing masonry by toothings to assure combined action of wa

and lining. Such toothings shall be distributed uniformly throughou

the wall and shall aggregate in vertical cross-sectional area not lm

than 15 percent of the total vertical area of the lining. Stresses i the masonry under the new conditions shall not exceed the allowabl

stresses prescribed in Section 4.2.2, Composite Walls. (See Apper

dix 11.8.2.)

11.9. Precautions During Erection.

11.9.1. Bracing to Resist Lateral Loads. Masonry walls i locations where they may be exposed to high winds during erectio

shall not be built higher than 10 times their thickness unless ade

quately braced or until provision is made for the prompt installatio of permanent bracing at the floor or roof level immediately above th

story under construction. Back fill shall not be placed agains

foundation walls until they have been braced to withstand the hor

zontal pressure. (See Appendix 11.9.1.) 11.9.2. Wetting of Brick. Brick (clay or shale) shall be wette

when laid unless their gain in weight resulting from partial immersio

flatwise in }{ inch of water for 1 minute is less then % ounce per 3 square inches of immersed area. (See Appendix 11.9.2.) 11.9.3. Protection Against Freezing. Masonry shall be pre tected against freezing for at least 48 hours after being laid. Unles

adequate precautions against freezing are taken, no masonry shall b

built when the temperature is below 32 F. on a rising temperature, c below 40 F. on a falling temperature, at the point where the work i in progress. No frozen materials shall be built upon. (See Appendi

11.9.3.)

Appendix

The Appendix consists of explanatory matter referring to variou

parts of the recommended code requirements. It is not a part of th

American Standard Building Code Requirements for Masonry bu

is presented as background material for users of the standard. i certain amount of material describing "good practice" is includec

The subdivisions of the Appendix are numbered to correspond wit; the section numbers of the standard.

1.3. Dimensions. For information on modular dimensions se American Standard A62.1-1945, Coordination of Dimensions c Building Materials and Equipment [l], 4 and A62.2-1946, Sizes c Clay and Concrete Modular Masonry Units of the American Stand

ards Association [2]. The intent of Section 1.3 is to avoid unnecessary repetition of th

adjective "nominal" before each nominal dimensional requirement i:

4 Figures in brackets indicate the literature references on page 37. IS
the standard, if the dimension is not nominal, the adjective "actual"

lis used. At the present time (1953) the thickness of mortar joints is considered to be not exceeding % inch when used with structural clay

(products, not exceeding % inch for concrete block and % or % inch for

lass block. The dimensions for concrete as specified in the standard

re usually actual in practice, but when used with masonry units, as

in foundations supporting masonry, or in spandrels combining concrete and masonry, the dimensions should be considered as nominal, with

the difference between "nominal" and "actual" corresponding to the

thickness of the mortar joint used with the unit under consideration.

1.4. Alternate Materials and Constructions. Procedures for approving new constructions having merit should be as simple as

possible so that use of such constructions, when justified by available

imformation or by readily ascertaininable facts, will not be retarded

unduly. If records of service performance covering a period of several years, or the results of laboratory or field tests that either are

similarly time-consuming or of prohibitive cost, are required as proof

bf acceptability, the development and utilization of improved or less postly materials and methods will be discouraged. On the other hand,

Perfunctory or otherwise inadequate investigations and requirements

-elating to novel constructions may lead to unsafe structures.

I' It appears to be the consensus of experts that the desired objectives

y ill not be attained by insisting that all new construction proposed

for use be subjected to precisely the same kind of examinations and

:ests and be required to conform to the same limitations. In many

Instances, opinions of structural and materials engineers may be of nore value in estimating the durability and other essential properties

jf an untried construction than the results of simple routine tests. Accordingly, detailed directions for investigating the adequacy of new

constructions are not given, nor are all pertinent properties listed. i definite size of wall panels for structural tests and methods for conducting these tests are recommended in the belief that standardisation of these features will be of assistance in interpreting the results tnd will tend to minimize the need of making separate tests in each

)f many different localities.

It is necessary to guard against unqualified acceptance of data on

strength of masonry built from unusual shapes or combinations of

inits unless satisfactory evidence is made available concerning the

d entity or relation between the workmanship used on the specimen

ubmitted and workmanship that may be reasonably expected in ommercial construction. If the bed joints in masonry specimens

Submitted for test had been leveled or if coverage of hollow units

' ricludes webs and longitudinal shells, either new test specimens should

jre constructed according to prevailing methods or the factor of safety

hould be increased beyond the 4 given as a minimum in Section 1.5.3.

will suggested procedure is to consider that the strength of masonry

jmilt with commercial workmanship is proportional to the ratio of

v jlhe area given a firm bearing by the mortar to the gross area, and to iscount accordingly the values determined on masonry built with

'superior workmanship" such as described in BMS 5 [3].

: Suitable methods of testing masonry walls for strength are described

| ASTM E 72-51 T, Tentative Methods of Conducting Strength

' &ests of Panels for Building Construction [4].

19

"it
1.5.1. Tests—When Required. In other sections of the standard,

requirements are set forth covering the quality of materials to be

used in buildings. The purpose of Section 1.5.1 is to give the building

official authority to require tests of materials and constructions when

there is doubt of their quality or their conformity to the intent of the

standard. Under the provisions of this section the building official may require tests to be repeated if at any time there is reason to believe that a material or construction no longer conforms to the

requirements on which its approval was based. For the most part

the specifications for materials referred to in the standard include I standard methods of testing or refer to standard methods. The

building official should insist on strict adherence to these standard

methods in all official tests. Differences in the color and structure of masonry units should not J be considered a sufficient basis alone for rejection since such differences

may be caused by differences in the chemical composition of the raw

materials from which the units are made and may have no relation

to the strength, durability or other significant physical properties of the units. ' 2. Materials—Reference to Standards. Modern, well-written

building codes are characterized by a liberal use of nationally rec-

' ognized standards. Through their use the code writer benefits

from the work of committees of national organizations having much 0 better facilities for gathering and evaluating data than local com- ] mittees can be expected to possess. Moreover, the use of nationally 1 recognized standards tends toward greater uniformity in codes through- [ out the country, an important consideration to designers, builders, and j producers of material who do work in more than one locality.

Although there are several methods of utilizing nationally recognized [l standards, a specific method of adoption by reference has been f employed in this standard. The standard is referred to by title, serial, designation, year of adoption, and the name of the sponsor M organization is given. Some critics of earlier drafts of the A41 1 standard favored a more general reference to national standards by

stating that the standard "as amended from time to time" should i apply. The expedient is not regarded favorably by many authorities 1 on the subject, however, because of the possibility that the courts s will refuse to uphold an ordinance utilizing such a method of reference u on the ground of uncertainty as to what edition of the standard is o meant, and as an improper delegation of legislative authority. While s this procedure might be suitable for an ASA standard that would be in used only as a reference document, the possibility that the ASA ;o standard might be copied verbatim into a local code has also to be sei considered. For a discussion of the use of standards, see NBS I Building Materials and Structures Report BMS116, Preparation lol and Revision of Building Codes [5] by George N. Thompson, National U\ Bureau of Standards. ID Constitutional provisions affecting the adoption of standards by i reference vary in different States and legal opinion is somewhat tl divided on the question. Hence, it would be well for code writers to ]\{ consult the appropriate law officer before adopting any method of si utilizing recognized standards, and to ascertain whether the procedure [ has legal sanction in order to avoid possible later attack on the method m employed. Inti

20
2.1.1. Second- Hand Materials. Irrespective of the original grading

(of masonry units, compliance with code requirements of material

iwhich has been exposed to weather for a term of years cannot be

lassumed in the absence of test. Much salvaged brick comes from the

demolition of old buildings constructed of solid brick masonry in

i\vhich hard-burned bricks were used on the exterior and salmon brick

as back-up, and, since the color differences which guided the original

brick masons in their sorting and selecting of bricks become obscured

with exposure and contact with mortar, there is a definite danger

that these salmon bricks may be used for exterior exposure with

consequent rapid and excessive disintegration. Before permitting

their use, the building official should satisfy himself that second-hand

materials are suitable for the proposed location and conditions of use. The use of masonry units salvaged from chimneys in not recommended,

tince such units may be impregnated with oils or tarry material.

2.2.1. Building Brick.

ASTM Specifications for Building Brick (Solid Masonry Units

Made from Clay or Shale), C 62-50, provides essentially a classifica- tion for durability. The classification by strength given in Section 2

pf this specification is the one used in this standard.

From the standpoint of durability the grades of ASTM Specifications

l|or Sand-Lime Brick, C 73-51, are equivalent to the corresponding

grades of ASTM C 62-50. Sand-lime brick differ from brick made

rom clay and shale in that the compressive and transverse strengths

M sand-lime brick are much better correlated with the results of

(Jurability tests than are the same properties of brick made from clay

tnd shale. Like certain concrete units, high-strength sand-lime

prick tend to gain strength during laboratory cycles of freezing and

^hawing [6]. Few, if any, data have been obtained on the durability of concrete

pricks tested as bricks. The results of numerous tests on mortars

nd concretes warrant the conclusion, however, that the requirement

or the grade A brick of ASTM C 55-52 will reasonably insure durability where exposures correspond to those considered in this standard.

1STM C 55-52 does not provide a minimum age for test. It may be

ssumed, however, that the physical requirements specified apply to

material "at the time of delivery." The objection to the use of

ioncrete bricks at early ages is based upon the observed tendency for

[xcessive shrinkage rather than upon low strength. Steam curing

Kinder pressure is considered to be advantageous both from the standI'loint of decreasing subsequent shrinkage and increasing early strength.

|ee discussion of concrete masonry units. (See Appendix 2.2.3.)

I Since temperature must drop below 32 F for freezing to occur, it hollows that in those sections of the United States where temperatures

pldom fall below freezing, the degree of durability called for by grade

|1W of ASTM C 62-50 and ASTM C 73-51 and grade A of C 55-52

: j unnecessary for walls above grade. Those portions of the South

Atlantic States excluding mountainous areas, the Gulf States, and the

pacific coastal region would not require compliance with grade MW

is far as resistance to frost action is concerned.

Laboratory experiments also indicate that the effect of freezing and

hawing cycles in producing disintegration is related to the degree of

jituration of the test specimen while being frozen [7]. The nearer the

21
water content of a porous body approaches complete saturation (all pores completely filled), the greater the tendency to fail when frozen. ] High saturations result from continuous contact with or immersion

in water or intermittent wetting under conditions such that moisture

does not escape from the unit. Masonry may become highly saturated

if it is in contact with water-bearing soil, as in a retaining wall or foundation, or is in parapet walls poorly protected on their upper

surface and is sealed by a through flashing and an impermeable coating, such as oil paint or bitumen, on one or both of the vertical surfaces. Numerous instances have been noted where disintegration of the inside face of a parapet followed sealing.

When water is in contact with a surface of a dry unit, water tends

to enter the unit by capillarity. If there is enough water and the}

time of contact is sufficiently long, the water will strike through from s face to face, giving a degree of saturation equaling or exceeding that

resulting from a 24-hour submersion in water at room temperature,,? This wetting through from face to face describes the condition of being,

"permeated" referred to in ASTM C 62-50. In the absence of defective workmanship, masonry protected from above by flashing and

with only one vertical surface exposed is unlikely to be permeated,,,

with water by ordinary weather. An additional degree of safety

results from the probability that freezing weather will only occasion-j

ally follow a heavy and long continued rain without some intermediate

drying. In general, units with high rates of absorption have corres-j

pondingiy rapid rates of drying. The probability of permeation is|- obviously affected by the amount and nature of precipitation. Pre-j

cipitation as snow would not introduce water into vertical surfaces. ASTM C 62-50 takes account of this probability by suggesting the f| use of grade NW bricks for exterior exposure where the average annual ?i precipitation is less than 20 inches. Disregarding snow as precipita- m tion, that portion of the United States west of a north and south Jj line through the center of Kansas can in general be considered as \ having an annual precipitation of less than 20 inches.

2.2.3. Concrete Masonry Units. Concrete block and concrete brick Dj are subject to shrinkage upon drying. The amount of this shrinkage

in masonry is a function of the moisture loss from the units after theL

time of laying and also varies with the nature of the aggregate and|\

method of curing. To minimize shrinkage of walls the units must be I] sufficiently dry when laid. Such a condition of units may be obtained

•

by drying unlil the desirable moisture condition is attained. High^

pressure steam curing in autoclaves is helpful in producing units oL[

relatively low moisture content and low shrinkage and moisture vol-L[, r ume change properties [8, 9]. In either case the units must be prop-, ( erly protected from moisture gain on the job. j;3D 2.2.4.2. Natural Stone. With respect to stone, the term "dura-j^

bility" should be understood to include resistance to all weathering; j, agents to which the stone is exposed, and in cases of steps, floors, ] etc., resistance to abrasion. Weathering agents of most concern arej[

(1 heat, cold, moisture, and atmospheric gases. The question of dura-{;lj bility for a given stone can usually be settled by examining structures showing the stone under use similar to those proposed. For such c studies the stone producer or local stonesetter should be called upon ^

for a list of structures. Untried stones under consideration fo%;

"0 hat

22
I

important structures should not be used before thorough testing in

the laboratory.

2.3.2. Plain Concrete. The best general measure of the resistance

of concrete to freezing and thawing and to weathering is the quality

(of the cement paste as determined by the proportion of water to cement. _ However, for a given water-cement content the resistance

is materially increased by air entrainment. Maximum water contents specified give good resistance with normal concrete and all types of sound aggregate. Higher water content can be used with

[l lair entrainment, under some climatic conditions, or with some aggregates. Where satisfactory results with greater water content can be

j shown by tests or experience, such concrete should be permitted.

*Since allowable stresses are given as a function of the compressive

strength of the concrete, the factor of safety remains the same regardless of the strength of the concrete and only nominal minimum

strength requirements are necessary. This permits the safe use of relatively weak lightweight concrete where the strength is not as important as other properties such as insulation.

3.1. Quality of Mortar. The 1944 edition of this standard pre- sented an abbreviated specification for mortar and described in the

appendix (2-14) the theory and application of the "flow after suc- tion" test. The present standard substitutes for this material refer- ence to ASTM Tentative Specifications for Mortar for Unit Masonry

(C 270-52 T). 5 This specification follows rather closely in content

the one outlined in the 1944 edition. Among the changes are the

insertion of a new grade of mortar (A—2) between the oiiginal A

mow A-l) and B grades. In the "proportion requirements" a mortar proportioned 1:1:6 poitland cement-Type II masonry cementsand by volume is considered equivalent in strength to one 1:1/4:3

Portland cement-lime-sand by volume, and the Type A-2 mortar as

'either 1:2:9 port-land cement-Type II masonry cement-sand or a 1:1/2:4-1/2 portland cement-lime-sand mixture by volume. The

"property requirements" specify that an A-2 mortar have a strength

bf not less than 1800 psi at 28 days. The minimum strengths for •Type B and Type C mortars have been raised from 600 to 750 psi

-and from 200 to 350 psi respectively. The oiiginal low values in ;A4 1.1-1 944 had been set so that all cement-lime mortars of a partic-

>ular specified composition could be expected to pass the requirements

^for compressive strength given for that composition. It was found

-m practice that special methods of cure were used which gave higher

strengths for Type C so that mortars of this composition qualified

and were used as Type B mortars. Since C 270-52 T now specifies

|>| 'damp closet" curing for Type B and Type C mortars instead of ?uring in water as specified in the earlier edition, increase in required

strength for these mortars may be regarded as taking account of a hange in test method rather than as an upgrading in strength. The

:1:6 moitars used in the wall specimens whose tests supplied the

'lata upon which the allowable compressive stresses for solid brick

'nasonry were based, averaged over 1,000 psi. These mortar speci- mens were cast at "mason's consistency" as 2 by 4-inch cylinders

Ifind were cured in water [10].

]

8 The substitution of Type II Masonry Cement for Type I Masonry Cement in "C" mortar as given in Table II on page 385 of Part 3 of the 1952 Ecokof Standards is believed to be an inadvertence. It is expected

! hat this will be corrected in a forthcoming revision of C 270-52 T.

23
For the convenience of the reader, the requirements for mortar

given in ASTM Tentative Specifications for Mortar for Unit Masonrv

(C 270-52 T) are given in table 1. Table 1. Mortar requirements

Mortar

type

A-l.

A-2.

B__

C__

Parts by volume

Port- land cement Masonry cement

1 (type II)

1 (type II)

1 (type II)

1 (type I or type II) a

Hydrated

lime or lime putty

Over % to Over y2 to iy4 Over 1%

to 2}{

Over 2^

to 4

Aggregate measured in damp, loose condition

Not less than 2% and

not more than 3 times the sum of the volumes of the cements and lime

used.

Miaimum

average compressive

strength of three 2-in. cubes at 28 days

psi

2, 500

1, 800

750

350

75

a The correction referred to in footnote 5 is made in the above tabulation. Mortars meeting the proportion requirements in table 1 and composed of ingredients conforming to the applicable ASTM specifications are assumed to meet the compressive strength requirements

listed in the last column and to have water retentions of not less than 70 percent when mixed to an initial flow of 100 to 115. The

selection of mortars can be made either by specifying ingredients and

proportions or by specifying compressive strength and water retentivity.

Specification C 270-52 T in its present form provides little protection against unsound (expanding) mortar. Although Portland

Cement (C 150-49) and Natural Cement (C 10-49 T) must meet

a 0.50 percent limit on autoclave expansion, the specifications for Masonry Cement (C 91-51) 6 and Hydraulic Hydrated Lime (C 141-42)

provide only "pat tests" for soundness. The Specification for Hydrated Lime for Structural Purposes (C 207-49) covers both

"Special" and "Normal" hydrates. A dolomitic "normal" hydrate

usually contains a considerable quantity of unhydrated magnesium

oxide which may cause damaging expansion upon conversion to magnesium hydroxide in a hardened mortar [11]. "S" (special lime)

which includes both high-calcium hydrate and autoclaved dolomitic

hydrate has negligible expansion. Masonry cement containing

excessive unhydrated magnesium oxide or made from portland cement

clinker not passing the soundness test prescribed in C 150^9 may

also cause expansion in mortar.

3.4. Types of Mortar Permitted. The selection of mortars per- mitted for the several kinds of masonry listed in the table is, for the

6 A tentative revision of this specification was approved in 1953 to provide a 1.0 limit on autoclave [ expansions on specimens tested at age of 7 days. See page 4 of the 1953 Preprint of the Report of ASTM \. Committee C-l on Cement. 24
purposes of this standard, based upon compressive strength. It should

not be assumed that higher strength mortars are preferable to lower

strength mortars where lower strength mortars are permitted for particular uses. See, for example, appendix material on Workmanship,

Section 4.2.1. The recognition of Type D mortar in the standard has been questioned. The objections to the use of low strength mortars such as Type D, are based upon the record of behavior of masonry laid with

such mortars when subjected to lateral forces as in earthquakes,

its poor resistance to weathering when exposed to freezing in the

presence of moisture and its deficiency in hydraulicity (hardening in

the presence of moisture). In consideration of the redefinition of Type D mortar as a mixture of portland cement and lime (1:4:15

by volume) instead of the straight lime mortar (1:3) as used in the

1944 edition of the standard, its use is continued although subject

to considerable restriction as heretofore.

There is evidence indicating that mortar in walls other than parapets

or foundations is not ordinarily subject to severe weatheiing even though the prevailing climate provides high precipitation and freezing

temperatures. The requirements for wall thickness and lateral support

where Type D mortar is permitted, are considered to provide safety

except in structures designed to withstand high lateral forces such

as from earthquakes.

4.2 Allowable Stresses. Except for the interpolation of compressive stresses for masonry laid with Type A-2 mortar, the figures for

brick and stone masonry remain unchanged from the 1944 edition

of the standard. In the absence of comparable data on the strength

of masonry laid with A-2 mortar, the arithmetical means of the A-l

and B values are used.

The stresses for brick masonry in the 1944 edition of the standard were copied from the 1931 "Modifications in recommended minimum

requirements for masonry wall construction of the Building Code

Committee of the Department of Commerce" [12] and values for stresses for brick laid with C mortar were interpolated. These

stresses were based upon data provided by the National Bureau of Standards [10] compared with earlier values (Compressive Tests on

Brick Masonry—A compilation of data covering 708 individual tests

1 of brick masonry in the form of piers and walls, prepared by the

Building Code Committee of the XL S. Department of Commerce).

These studies showed the importance of workmanship as a factor in the compressive strength of masonry. In the 1931 modifications an

attempt was made to take account of this factor by the provision

"that where the masonry is laid with smooth level horizontal joints

and completely filled vertical joints and is thoroughly inspected and

where the effects of eccentric and concentrated loads and lateral forces are fully analyzed and allowance made for them, the working

stresses in this table may be increased by 50 percent." This allowanc? was omitted in A41. 1-1944 because it was found that "smooth level horizontal joints'' were practically unobtainable under field conditions

(See Appendix 4.2.1 on Workmanship) and furthermore, that certain

code authorities and designers were assuming that the workmanship

described above was standard.

The selection of allowable stresses for brick masonry for the 1931

modifications was based essentially on the following considerations.

All available data on strengths were reviewed and classified according

25
to gradings of brick strength and mortar strength. A wide scatter of strength was found within these grades even when brick strengths

and mortar types did not significantly differ. After elimination of scattered low strengths which appeared to result from faulty test methods or the use of nonstandard material, insofar as could be determined from Soudy of the original reports, values were set such that

masonry made of brick and mortar within the classification limits considered, could be expected to exceed the established minimum strength

for 95 percent of the tests. Consideration was given to the relation

between loads at first crack and ultimate loads where data were available. The following values were established and accepted by the

Department of Commerce Building Code Committee:

Brick grading

Assumed compressive strengths with

cement-lime-sand mortars

1C:1/4L:3S 1C:1L:6S 1L:3S

psi

8,000 plus _ 4,500 to 8,000

2,500 to 4,500

1,500 to 2,500

psi

2, 000

1, 000

700

500

psi

1, 200

800

560

250

psi

800

400

275

150 The allowable stresses were established by applying factors of safety

of from 3 to 5 to the above values. The lower factors of safety were used where low strengths had resulted from the use of brick and

mortar of low strength. In general, the higher the strength, the

greater the variability.

The data on strength of masonry built of structural clay tile and

concrete masonry units were reviewed and working stresses in compression have been selected so that the minimum safety factor with

concentric loading is about 3% [3, 13, 14, 15, 16]. The values for grouted solid masonry follow those of the Pacific

Coast Building Officials Conference excepl that values are given for the use of "B" mortar [17]. Relatively low limits are placed on the

allowable compressive stresses on the gross areas of cavity walls,

since loading is usually on the inner wythe only.

The working stresses for stone masonry are traditional. The values

given are from the 1909 Edition of Baker's "Masonry Construction" t and represent the estimated loads on a number of existing stone struc-

( tures, for the most part bridge piers.

Proposals for allowable stresses for shear and for tension in ex- treme fiber in flexure in unit masonry have been considered by the

f Committee. But until agreement can be reached as to appropriate

values for allowable tensile stresses under various conditions, it is considered prudent to neglect the tensile resistance of non-reinforced

masonry. The usefulness to designers of an assumed strength in tension is well understood. The disagreement is over the basis of estimating tensile strength in the absence of tests and assigning a reasonable value. For concrete there is a fairly uniform relation

between compressive strength and tensile strength. The 3 percent

" allowance for tensile stress in flexure (Section 4.2.3) represents a factor

26
[ of safety of about five. No such relation can be said to hold for unit

jmasonry. Except for very low strength mortars, failure in tension

usually takes place at the interface between the mortar and the unit. Numerous tests on two-brick assemblages have shown that strength

jin tension depends upon a number of factors. There is general agree- ment that the "initial rate of absorption" (suction) of the unit is very

important [18]. Flowability of the mortar is at least equally important; very weak and incomplete bond is obtained with mortars having insufficient mixing water [19, 20]. Among other factors are "water retentivity" and strength of the mortar, extent of bond and

the nature of the surface of the unit in contact with the mortar. Delay in placing units on an already spread bed of mortar and moving the unit after it has been laid in place are known to lower or comjpletely destroy bond. Curing with the joint under load increases

bond strength [21]. Most of the data on the transverse strength of

solid masonry walls (4 to 6 ft long and from 8 to 12 ft high) are summarized in "Brick and Tile Engineering" [22] by H. C. Plurnmer.

These data do not, however, permit evaluation of the relative effect of "superior workmanship", rate of absorption of the bricks, and

strength of mortar. With 4 exceptions, all of the 50 walls were laid

with "superior workmanship" which, as far as defined, included complete filling of all joints and leveled bed joints. (See BMS5 [3] for description of workmanship.) All reported data are on specimens

built and cured in the laboratory.

Obviously the probability that masonry may crack in service must

|be considered. Among the commonly accepted and familiar causes

bf cracks are "foundation settlement, deflection of beams, overloading, expansion and contraction with temperature change, and various

features of faulty design and construction." In addition, cracking of structures has been ascribed to shrinkage of concrete masonry units,

expansion of mortar either from unsound ingredients [11], or from

reactions of the cementitious material with sulfates and the "moisture

expansion" of certain clay products. "Moisture expansion" was

demonstrated by Schurecht [23, 24] on architectural terra cotta. The same reaction has been noted on a few structural clay tile. The

possibility of unsoundness as indicated by volume change exists for almost all of the materials used in masonry. The history of research

in this field presents numerous illustrations of the discovery of hitherto

unknown and unsuspected behavior of materials resulting from unusual combinations of factors. The "alkali-aggregate" reaction is an

example [25]. Troubles resulting from lapses in manufacturing control or the accidental inclusions of unsound ingredients are rare but

are always possible. In the present state of materials specifications,

(the safeguards against some of these causes for volume change are Inadequate or nonexistent. This, plus the quality of control of masons' techniques in practice, would indicate the desirability of

jusing reinforced masonry where lateral stability is required beyond

'What is provided by the present standard.

4.2.1. Higher Stresses.—Effect of Workmanship on Properties of

Masonry. From a comparison of the compressive strengths of brick

walls, alike with respect to bricks and mortar but differing in the

techniques used by the masons, the following conclusion was drawn

; 26] : Workmanship characterized by filled head (vertical or cross)

'joints and completely filled and leveled (unfurrowed) horizontal bed

27
joints gave an increase in compressive strength over the results of workmanship characterized by unfilled head j oints and deeply furrowed

bed joints of from 24 to 112 percent.

The commercial practicability of laying brick on completely filled |: and leveled bed joints was investigated with the help of a Washington,

D. C. mason contractor. This contractor's practice was to guarantee P compliance with and use of a specified quality of workmanship.

His original specification was written around the description of the : "A" workmanship given in Building Materials and Structures Report n BMS7 [27] and his service included continuous supervision of the masons b}T qualified inspectors. The contractor reported after some n months that brick masonry could not be commercially laid without some degree of furrowing of the bed joint. Tapping bricks down to line was difficult and adjustment of thickness of the mortar bed took ' time with resultant stiffening of the mortar. Since further study f (BMS82) [28] had demonstrated that "there was no significant 30 difference in the permeability of brick walls in which mortar for the as bed joints was leveled or furrowed before placing the bricks, sufficient mortar having been used to cover the bricks," and the commercial ll impracticability of requiring leveled bed joints had been demonstrated, J the "A" workmanship described in BMS82 is recommended as a if standard of good workmanship in place of the "A" workmanship Si described in RP108 and BMS7. | The compressive strength of masonry of block or tile depends Jp importantly upon the completeness with which the units are p bedded. For end-construction masonry, the bedding has ranged h from covering the two face shells only, to complete coverage of the c ends of all shells and webs. The effect of quality of workmanship : on the compressive strength of tile masonry is well illustrated by

available test data. For example, NBS Technologic Paper 311 [14] reports the results of tests of some end construction walls for which id the mason had bedded the longitudinal shells of the tiles but made o no attempt to obtain mortar bearings for the webs or the transverse 1< shells, and of other walls for which mortar bearings were provided jji for all shells and webs. References [3, 15, 16, 29] give some data ti on the compressive and transverse strength of walls built with1 [1 concrete block. Mortar bedding for test walls of side construction in tile has ranged from complete coverage of the bearing shells to only la a strip of mortar about 1% inches wide along the faces of the walls. Mortar was provided on the ends of the shells in both faces of the |a walls for the vertical joints.

The data that have been reported on strength of masonry under m

transverse loading (see Appendix 4.2) do not permit an evaluation of ssl workmanship. If it be granted that failure in tension usually takes n

place at the interface between the unit and the mortar, it is evident liii that tensile strength is a function not only of adhesion but also of area bonding (degree of completeness of filling of the joints).

Requirements for minimizing the entrance of water into masonry jp (prevention of wet walls) have not been found in any of the building ~ codes so far examined. Although dampness in a structure is generally

recognized as bad from the standpoint of comfort and health and there

is evidence that the durability of masonry is seriously affected by

freezing and thawing and by leaching and crystallization of salts if much moisture is present [30, 31], the subject is not included in

28
codes possibly on account of uncertainty as to the legal status and

enforceability of such provisions. The building official, however,

is sometimes blamed for leaking masonry on the theory that such

conditions are the fault of lax inspection. The following discussion of the factors concerned with building leak-proof masonry is presented

for information.

(1) The rate of absorption [28, 32, 33, 34] of brick is very important.

Either bricks should be selected having a rate of absorption (grams of water absorbed in 1 minute by 30 sq in. of brick surface when set in

% in. depth of water) of under 20 g when dry (some authorities recom- mend 10 g) [28], or the rate of absorption of the brick should be lowered

to this figure by wetting before laying.

(2) The mortar should be easily workable (plastic) and have a high

water-retaining capacity. These two properties usually are associated.

Harsh working mortars will usually both "bleed" (permit separation

of water from the mortar) when used with impervious units and quickly

stiffen when laid in contact with porous units. The flow after suction

j (measure of water retentivity) should not be less than 70 percent.

\ For cement-lime mortar, the lime should be as plastic as is obtainable.

| Type "S" lime of ASTM C 207-49 (Hydrated Lime for Masonry Puri poses), Special Finishing Hydrated Lime (ASTM C 206-49) and a high-calcium lime putty sufficiently aged so that it will meet the

plasticity requirement given for "S" lime in C 207-49, have the desired

• properties. Masonry cements meeting the requirements of ASTM C

|91-52T would be of satisfactory workability. All mortar should be

: mixed and kept tempered so that it will contain as much water as it

I can carry. The workability of the mortar should be satisfactory to

I the mason.

(3) To obtain brickwork impermeable to water, all bed and head

joints in both facing and back-up should be completely filled with

.mortar. Bed joints are satisfactorily filled by spreading a thick bed

• of mortar and making a shallow furrow. (See previous discussion on

' leveling of bed joints.) The permissible length of spread of a bed

i joint and the resulting delay in placing the last brick will depend upon

» the suction (rate of absorption) of the bricks. If the suction is under

10 grams, a 3-foot (4 brick) length is satisfactory. If bricks with

Irates of absorption exceeding 20 grams and uncorrected by wetting

are used, the length of spread of the bed joints should be reduced.

(4) The recommended procedure for filling head joints is to apply

S a heavy buttering of mortar on one end of the brick, press the brick

down into the bed joint and push the brick into place so that the morJtar squeezes out from the top and sides of the head joint. Mortar

ii should correspondingly cover the entire side of a brick before placing

las a header. Attempting to fill head joints by slushing or dashing is ineffective in securing watertight joints. Partial filling of joints by

I "buttering" or "spotting" the vertical edge of the brick with mortar

cut from the extruded bed joint is likewise ineffective and should be

I prohibited. Where closures are required, the opening should be filled .with mortar so that insertion of the closure will extrude mortar both

laterally and vertically.

(5) Tooling of joints is not a substitute for complete filling or a rem-

| edy for incomplete filling of joints. Proper tooling helps somewhat to

(resist penetration by water. A concave joint is best for the purpose.

I Avoid, if possible, the use of raked or other joints which provide hor29
izontal water tables. Mortar should be neither too stiff nor too fluid at time of tooling since if too stiff compaction will not take place and if too fluid the bricks may be moved. In the construction of impervious

masonry, bricks should not be moved after initial contact with mortar.

If out of line, remove brick and mortar and lay again.

(6) Back-plastering (parging) of the back face of the exterior wythe

before the back-up units are laid is recommended to help insure impermeable masonry. If the back-up is laid first, the parging should be

applied to the front of the back-up. The mortar used for back-plastering should be the same as that used in laying the brick and should be

applied from % inch to % inch in thickness. Attempting to fill the

cavity between wythes by slushing is not recommended for the reasons

that slushing is unlikely to completely fill the cavity and the mortar

is not compacted.

(7) Laboratory tests [28, 35, 36] have shown that plain masonry

walls of concrete block or structural tile one unit in thickness, when

laid with commercially practicable workmanship and without surface

protection or special design, leak when subjected to treatments simulating wind-blown rain. Descriptions such as "leaked rapidly" and

"highly permeable" were applied to the results of these tests. For

concrete block masonry, two coats of cement-water paint [35] applied

by means of stiff fiber brushes to the outside face made such walls

"practically impervious as long as the paint remained in good condition." Fishburn [37] confirmed these results. Coatings such as stucco on the face or a parging of cement mortar were also effective. Properly designed and constructed cavity or grouted walls usually

provide good protection from moisture penetration. The paper by

Tippy [38] and its discussion, presents recommended practice in concrete masonry wall construction. Corresponding recommendations

for structural clay tile masonry are given by Plummer [22]. For

moisture-proofing of walls below grade see Section 6.4. (8) An important item in the design of masonry for preventing

penetration by water is the provision for adequate and properly

installed flashings at vulnerable points of the wall. Reference is made

to Vol. 1, No. 10, October 1950 of Technical Notes on Brick and Tile

Construction (available from the Structural Clay Products Institute,

1520 18th St., N. W., Washington 6, D. C.) for recommended pro- cedures for flashing structural clay masonry. Corresponding information on flashing of concrete masonry is presented in the 1951

Edition of the Concrete Masonry Handbook (available from the

Portland Cement Association, 33 West Grand Avenue, Chicago 10,

111). See also Appendix 11.7.

4.2.2. Composite Walls. Limiting the allowable compressive stress

in a composite wall to that allowed for one of its vertical elements seems to be a reasonable restriction, although the results of some

tests [16] under short time and concentric loading indicate an average

strength somewhat higher than the strength of the weaker element. In service the portions of a wall composed of dissimilar materials may

undergo unequal movements with change in temperature and moisture

content and thereby cause lateral distortions and a varying distribution of stresses under constant load. However, long experience with

faced walls and with structures composed of different types of masonry

materials indicates that such movements are not large enough to endanger the stability of walls built in accordance with these recom30
mendations. Another reason for this requirement is the fact that the

resistance of a wall to lateral loads, causing tensile stresses in the weak

element of a composite wall, depends largely on the tensile strength

of that element.

4.2.3, Allowable Stresses in Plain Concrete. See Appendix 4.2, also references [39, 40].

5.1. Ratio of Height or Length to Thickness. Available data [20,

40, 41] indicate that metal ties of the type specified do not have

sufficient flexural rigidity to transmit shearing forces across the cavity.

- Consequently, when one wythe is subjected to a vertical load, only a small part of the load is transmitted to the other wythe, and the two

wythes do not exert common reaction under such loading.

Although the committee is aware of the desirability of more rational

methods of design than the arbitrary limitations on the ratios of wall

thickness to distance between lateral supports, it was considered that

1 more basic information is needed before they can be formulated.

Quantitative data are needed on the chief factors which affect lateral

; stability and the resistance of walls to lateral loads. To fill this need

many more tests will need to be made, some of which will provide

i additional information on the effects of conditions at the boundaries

i of walls [41].

6. Thickness of Masonry. This section combines the material on

- thickness presented in Sections 5, 6, 7, 8, 9, 11, and 12 of the 1944

; edition of the standard. The requirements on bond and bonding in these sections are brought together in Section 7. The original Section

10 on veneered walls will be presented in part as a separate standard

covering veneer not exceeding 1% inches in thickness. See Section 9

| of the present standard.

6.3.2. Thickness of Nonbearing Partitions. Section 6.3.2 replaces

i the table in Section 16-2 of A41. 1-1944 by a uniform relation between

thickness of the partition and its maximum unsupported height (or

length). Inclusion of thickness of plaster as part of the thickness of the partition somewhat liberalizes the restrictiveness of 6.3.2 in comparison with the former 16-2.

If lateral support for a partition depends upon a ceiling, floor, or

roof the top of the partition should have adequate anchorage to trans- mit the forces. This may be accomplished by the use of metal

- anchors or by keying the top of the partition to overhead work by

mortar or otherwise. Some building codes accept suspended ceilings as providing the required lateral support. These codes (Los Angeles

County Building Laws, 1953 Edition, for example) contain the additional requirement that anchorage shall be capable of resisting a horizontal force of 150 pounds per linear foot of wall. The committee

j has made no investigation of this matter.

I 6.4. Foundation Walls.

The importance of building basement walls and floors so that the

basement area will be sufficiently dry for its intended use needs to be

mentioned although this aspect is not, strictly speaking, within the

I scope of the standard. Foundation walls enclosing unexcavated areas

• generally require no special waterproofing measures but such measures

I frequently are deemed necessary or at least desirable with respect to basement walls and floors. The accompanying figure 1 shows details which in the opinion of the Committee represent reasonable measures to insure a satisfactorily

| dry basement. The drain tile indicated in the center and right

31
UNIT MASONRY UNIT MASONRY

BITUMINOUS COATING ON 2-1/4" COATS OF

TYPE A-l OR A-2 MORTAR

-4"C0NC. SLAB

NO BASEMENT

5" LAYER OF GRAVEL, CRUSHED STONE

OR CINDERS 1/2" TO I 1/2" SIZE : \" LAYER OF 1/2° STONE, GRAVEL OR CINDERS LEVELED WITH 114 CEMENT GROUT WITH BASEMENT - NORMAL

SOIL AND OCCUPANCY

GRAVEL OR CRUSHED

STCNE BACKFILL, 12" DEEP OVER TILE

— WATERPROOF MEM3PANE

2 LAYERS WATER=ROOF

[ BUILDING PAPER BOPPED

! DOWN WITH HOT TAR OR ASPHALT

-DRAIN TILE

LAID WITH OPEN JOINTS WITH BASEMENT - VERY WET SOIL OR MORE

THAN NORMAL OCCUPANCY OF BASEMENT Figure 1. Means of preventing entrance of water into basements.

(Appendix 6.4.)

details of figure 1, should lead to a storm sewer or other outlet. See

also paper by Fishburn [42]. With reference to basement walls of cast-in-place concrete, it is good practice to coat the outer surface

with bituminous material but the plastei coatings shown in the details

for unit masonry walls should not be required.

6.4.1. Thickness of Foundation Walls.

The committee is aware that in somewhat rare instances, foundation walls conforming to the requirements of Section 6.4 may have

insufficient strength or stability to withstand the lateral pressures imposed, and that, on the other hand, the requirements may be more

restrictive than needed for some structures and soil conditions.

Aside from the transverse strength of the wall [14. 16, 22] (^see also Appendix 4.2 and 4.2.1.'), the factors which have the greatest

effect upon the lateral stability of a given wall are: (1) earth pressure,

(2) strength and rigidity of the lateral supports (usually the footing

and the first floor above), and (3) the vertical load on the wall. The

lateral pressure may be zero, or it may approach the hydrostatic

pressure of a liquid having the density of mud. When backfill is by bulldozer or other heavy earth moving equipment, lateral pressure

greatly exceeding the normal earth pressure may result. The probable maximum pressure for the foundation walls of a structure can

be estimated closely only by those familiar with the conditions at the site. Foundation walls of the materials and dimensions ordinarily used

are not stable against earth pressures unless restrained against horizontal movement at the top and bottom or along closely spaced

vertical elements. Usually the spacing of cross walls is too great for them to serve as the only lateral supports. Therefore, it is essential

that the floors be so anchored and connected as to restrain the top of the wall, and that the bottom be restrained at the footing:.

32
Vertical compressive loads on foundation walls resulting from the

weight of the building and its contents tend to prevent the development of or to reduce the magnitude of the vertical tensile stresses caused by lateral earth pressures. The resistance to lateral pres- sures of a given foundation wall is therefore increased by an increase

in the weight of the superstructure. For example, if the maximum

tensile stress in the foundation wall for a one-story light wood-frame

house were 20 psi, this stress probably would be reduced to 5 or 10

psi if the superstructure were changed to a typical three-story house

with 8-inch brick walls. The use of thinner foundation walls for

light structures than for heavy structures, as permitted by some

codes, is not justified by a consideration of lateral stability.

6.4.2.1. Foundation Walls of Reinforced Masonry. The transverse strength of walls of reinforced masonry not only may be greater than

for similar nonreinforced walls but it is also more uniform and

reliable. The information available [43] indicates that 8-inch walls

not more than 7 feet deep reinforced with %-inch round bars 2 feet apart, or the equivalent in smaller bars or wires, has adequate resist- ance under the conditions commonly encountered. The heights of the backfill against other types of 8-inch walls of unit masonry are limited to values related to their expected resistance to lateral pressures.

6.5. Parapet Walls.

The provisions of this section are intended to regulate only the

structural features of parapet walls. Other standards in the series of American Standard Building Code Requirements will specify

when parapet walls are required.

The limits on the ratios of height to thickness of parapet walls

specified in this section are believed to be safe for ordinary conditions.

In localities subject to high winds or to earthquakes, somewhat more

rigid restrictions may be advisable.

Particular attention should be paid to the flashing, dampproofing,

and workmanship of parapet walls to prevent disintegration. Through

hashing should be provided under the coping, unless the coping is of an impervious material laid with water-tight joints, and also at the

base of the wall. All joints should be well filled. Coating, or sealing

Df the back of the wall with vapor impermeable materials is not

recommended, as this practice prevents rapid drying of the masonry.

7.1.2. Bonding With Metal Ties. Figure 2 illustrates the staggering and spacing of metal ties according to the requirements of 7.1.2.

- 36" MAX.

MAX. AREA = 4^SQ.FT

Figure' 2. Spacing and staggering of metal ties.

33
BONDING COURSE -

BONDING COURSE

10"

LAPPING WITH UNITS AT LEAST 3

1" OVER

UNITS BELOW

LAPPING WITH UNITS AT

LEAST 50% GREATER IN THICKNESS THAN UNITS BELOW Figure 3. Types of bonding with hollow units.

7.2. Bonding of Masonry Walls of Hollow Units. Figure 3 illus- trates the type of bonding prescribed by 7.2.1.

7.7.4. Bonding of Nonbearing Intersecting Walls. Building codes

and construction practice allow considerable latitude regarding the

bonding or anchorage of ordinary interior nonbearing walls with inter-

:

secting walls or structural members. When built solidly against

floor and ceiling such partitions usually should derive sufficient lateral n bracing from these contacts. However, if the wall separates from the

ceiling due to settlement, contraction, or other causes, its lateral stability will be impaired and made more dependent on its connections

with other members. For this reason bonding or anchorage with

intersecting walls and members seems desirable. A few suggested k

details are shown herein (fig. 4) but there are various other details : which would be equally satisfactory and acceptable.

34
Regarding nonbearing walls which function as curtain walls, panel

rails, fire walls, or shear walls (walls affording lateral support) it is ustomary and good engineering practice that they be bonded or .nchored with intersecting walls and structural members in a a manner

.ssuring adequate resistance to the design lateral forces acting on the

onnection.

11.1.2. Fastening Joists or Beams. All floor beams should be

dequately anchored to the masonry wall and to each other. Anchors

•f iron or steel, or other suitable metal, for floor joists should be pro-

'ided at 4 foot intervals where floor joists are supported on masonry

alls. They should engage not less than half the thicKness of the

.all and should be solidly embedded in mortar. Interior ends of nchored joists should be lapped and spiked, or the equivalent, so as 0 form continuous ties across the building.

11.1.3. Spacing. Anchors tying walls to joists parallel to the

vail should engage not less than three joists. They may be inserted

hrough holes near mid-depth of the joists. 11.1.4. Anchoring Structural Members. Examples of adequate

nchorage are presented in Factory Mutual Bulletin of Loss Prevention No. 7.13, "Anchorage of Factory Roofs" [44]. 11.2.1.1. Chases and Recesses—Exceptions for 8-inch Walls.

he exception to the usual requirement that there shall be no chases

1 8-inch walls is made to provide for ducts of warm-air heating

5

rstems in dwellings and for the recessing of radiators under windows,

dnce the grilles must be located in exterior walls in many cases, and

nee the 8-inch wall is the common practice in dwellings, it was cemed necessary to provide space in the wall for the elbow of the

! uct where it makes the turn from the grille to the branch line located

etween the floor joists. The committee was of the opinion that

phases of the dimensions permitted in this section would not weaken

ie wall to any serious extent and would permit of some economy

nd convenience in the installation of the heating system. As no

85
load of any importance is carried by the masonry under the window

sills, it was felt that recesses for radiators could safely be permitted ! under the conditions set forth in this section.

11.7. Drainage of Hollow Walls. The following is quoted from

the Structural Clay Products Institute leaflet on Cavity Walls (Technical Notes on Brick and Tile Construction, Vol. 1, No. 6, June 1950):

Draining the cavity. It is important that the cavity be kept clear of mortar droppings during construction and that the mortar is not! permitted to bridge the air space between wythes. The bottom

of the cavity should be located above ground level, and the cavity

should be drained by weep holes in the vertical joints of the bottom

course of the outer wythe. The weep holes, spaced approximately I 2 feet apart, may be formed by leaving an open vertical joint be- tween units in the bottom course, or by other suitable methods.

Flashing. Good flashing details are particularly important mlc

cavity wall construction. Flashing should be installed over all wall openings, not protected by projecting eaves or hoods, tcj. deflect moisture outward through the outer wythe. The flashing 1 should extend 6 inches beyond the jamb on each side of the opening, j and weep holes provided to drain any accumulated moisture,

jp Continuous flashing should be installed at the bottom of the cavity

| to deflect any accumulated moisture to the outside through the weep holes. Where there is no basement, however, and the bot-ii torn of the cavity is above ground level and several inches be- jj: low the lowest bearing level of the first floor, no flashing need be |o provided, but a damp-course should be placed in both the inner

and outer wythe, one course above the bottom of the cavity and : below the bottom of the first floor joists. Where unit masonry

sills are used, flashing is advisable under the sills, and weep holeef should be provided.

11.8.2. Walls of Insufficient Thickness. Type A-l mortar is required for masonry added to existing walls to insure that the modulus]^

of elasticity of the new masonry will not be excessively low in comparison to that of the existing masonry. The modulus of elasticity of the masonry tends to increase with age. Furthermore, the original

!

masonry may be assumed to have undergone its maximum decrease!

in height from loading. A high modulus of elasticity of the new mortar ! would therefore lessen the probability of failure of bond between

the old and new masonry through shear resulting from shortening!

under load.

11.9.1. Bracing to Resist Lateral Loads. Section 19-3 of the 1944. edition of the standard required that "Except when carried independently by girders at each floor, no wall shall be built up more than 21 feet in height in advance of other walls of the building" and 19-6 of 2] the same standard prescribed "During erection, walls shall be adequately braced." Section 11.9.1 sets the limit in terms of height with

respect to thickness beyond which bracing is required. Justification

for this requirement is given in the article by Sweet [45] "Resistance

of brick walls to wind."

11.9.2. Wetting of Brick (Clay or Shale). The great importance

of the suction rate of the masonry unit and the consistency (flow- ability) of the mortar on the tensile strength and watertightness oi 5 masonry has been demonstrated conclusively [19, 20, 22, 28, 34].

\ 36
jfhe flowability of the mortar should be the maximum compatible with

ifficient use by the mason, and additional water should be added if iieeded to overcome the stiffening resulting from evaporation of some

the mixing water. Suction rates of clay or shale brick should be

^certained in advance of their use in construction. Methods of measurement may be similar to those used in specifications [33], but me following methods may be found more practicable in some instances. X rough but effective test for determining what bricks give improved

bond by wetting consists in sprinkling a few drops of water on the flat

f the brick and noting the time required for these drops of water to be

/jbsorbed completely. If this time exceeds 1 minute, wetting is not

Ijeeded. A refinement of this method consists in drawing a circle 1

)|ich in diameter on the flat of the brick with a wax pencil (using a 25-

pnt piece as a guide provides a circle of almost the exact dimension),

ime milliliter of water (20 drops) is applied to the surface thus limited

[;iid the time for complete absorption is noted [46]. If this time exceeds

fe minutes, the bricks need not be wetted; if less than 1% minutes,

i etting is recommended.

| Wetting of vitrified and semivitrified bricks or excessive wetting

>{f other bricks is undesirable because of resultant floating of the bricks

i)n.d "bleeding" of the mortar. A satisfactory procedure consists in

flaying a stream of water on a pile of bricks until water is observed

I) run from each individual brick visible in the pile. Unless the

tricks are exposed to conditions favoring the rapid evaporation of

jioisture, one wetting per day is sufficient. 11.9.3. Protection Against Freezing. The cold weather requirements or reinforced concrete given in Section 406 of Building Code Requirements for Reinforced Concrete, (ACI 318-51; ASA A89. 1-1951)

vovld apply in general to masonry. The use of calcium chloride (the

ry salt) in an amount not exceeding 2 percent by weight of the

liortland cement content of the mortar is permissible. If used,

assolving of calcium chloride in the mixing water is recommended,

^he effect of calcium chloride is to accelerate the setting and hardening

if the portland cement in the mortar. The lowering of the freezing

,oint by this material in the amount permitted is negligible. Addition

jjf salts such as sodium chloride (common table salt) should not be

Cermitted since they will cause efflorescence and may disintegrate

^he masonry by recrystallization.

References

[1] A62. 1-1945, American Standard Basis for the Coordination of Dimensions of Building Materials and Equipment, American Standards Association, Inc., 70 E. 45th St., New York, N. Y. 35C

\2] A62.3-1946, American Standard Sizes of Clay and Concrete Modular Masonry

Units, American Standards Association, Inc., 70 E. 45th St., New York,

i N. Y. 50<*

|J13] H. L. Whittemore, A. H. Stang, and D. E. Parsons, Structural properties of

six masonry wall constructions, NBS Building Materials and Structures Report BMS5 (1938). Superintendent of Documents, Washington 25, D. C. 20c

1 i[4] Tentative Methods of Conducting Strength Tests of Panels for Building

Construction, ASTM Designation E72-51T, ASTM Standards 1952,

part 4, p. 955.

[5] George N. Thompson, Preparation and revision of building codes, NBS

Building Materials and Structures Report BMS116 (1949), Superintendent

of Documents, Washington 25, D. C. 150.

37
[6] J. W. McBurney and A. R. Eberle, Strength, water absorption and resistance n to freezing and thawing of sand-lime brick, J. Research NBS 20, 6' (1938) RP1065.

[7] J. W. McBurnev and A. R. Eberle, The freezing and thawing test for building

brick, Proc. ASTM 38, 470, part II.

[8] Harrv W. Easterly, Jr., Shrinkage and curing in concrete masonry units

' J. Am. Concrete Inst. 23, 5, 393-404 (Jan. 1952).

[9] Relation of shrinkage to moisture content in concrete masonry units, Housing

and Home Finance Agency, Housing Research Paper 25 (1953). Super

intendent of Documents, Washington 25. D. C. 20<t. [10] A. H. Stang, D. E. Parsons, and J. W. McBurney, Compressiye strength o clay brick walls, J. Research NBS 3, 507 (1929) RP108.

[11] J. W. McBurney, Cracking in masonry caused by expansion of mortar, Proc ASTM 52, 1228-47 (1952).

[12] Modifications in Recommended Minimum Requirements for Masonry Wal ; Construction (1931). This is an amendment to Recommended Minimun

Requirements for Masonry Wall Construction, NBS Building and Housing

Requirements for Masonry Wall Construction, NBS Building and Housing

Publication BH6 (1924). An extensive bibliography of tests on masonn . is contained in an appendix to this publication.

[13] D. E. Parsons, Factors affecting the strength of masonry of hollow units

J. Research NBS 6, 857 (1931) RP310.

[14] A. H. Stang, D. E. Parsons, and H. D. Foster, Compressive and transverse strength of hollow-tile walls, Technologic Paper NBS 20, 241 (1925-26v T311. Out of print.

[15] R. E. Copeland and A. G. Timms, Effect of mortar strength and strength o; unit on the strength of concrete masonry walls, J. Am. Concrete Inst. 3. 551-562 (1932).

[16j F. E. Richart, R. P. B. Moorman, and P. M. Woodworth, Strength anc

: stability of concrete masonrv walls, University of Illinois Engineering

Experiment Station Bulletin No. 251 (1932).

[17j Uniform Building Code, Pacific Coast Building Officials Conference, Sectior,: 2406, Grouted Brick Masonry, p. 92 (1952).

[18] L. A. Palmer and D. A. Parsons, A study of the properties of mortars anc, bricks and their relation to bond, J. Research NBS 12, 609 (1934) RP683

[19] M. O. Withey, Recent experiments on masonn' building materials made ir. _ the materials testing laboratory at the University of Wisconsin, U. of Wis

Reprint 53 (1935); and Brick masonrv walls . . . factors affecting theii quality, U. of Wis., Reprint 180 (1951).

[20] H. R. Fbrkner, R. S. Hagerman, P. S. Dear, and J. W. Whittemore, Mortal _

: bond characteristics of various brick, Bull. Virginia Polvtech. Inst. 7C (1948).

[21] L. A. Palmer and J. V. Hall, Durability and strength of bond betweer mortar and brick, J. Research NBS 6, 473 (1931) RP290.

[22] H. C. Plummer, Brick and Tile Engineering, Handbook of design, Structural Clay Products Institute, 1520 18th St. N. W., Washington 6, D. C. (1950

[23] H. G. Schurecht, Methods of testing crazing of glazes caused by increases irj the size of ceramic bodies, J. Am. Ceram. Soc. 11, (5) 271-277 (1928).

[24] H. G. Schurecht and G. R. Pole, Effect of water in expanding bodies ol different compositions. J. Am. Ceram. Soc. 12 (9) 596-604 (1929).

[25] R. F. Blanks. Notes on the effect of alkalis in portland cement on the durability of concrete. Proc. Am. Soc. Testing Materials 43, pp. 199-220 (1943).

[26] J. W. McBurnev, Effect of workmanship on the strength of brick masonry. American Architect 132, 613 (1927).

[27] C. C. Fishburn, D. Watstein, and D. E. Parsons, Water permeability ol masonry walls, NBS Building Materials and Structures Report BMS7

(1938)/ Out of print.

[28] C. C. Fishburn, Water permeability of walls built of masonry units, NBS

Building Materials and Structures Report BMS82, Superintendent of Documents. Washington 25, D. C. 25i

[29] D. S. Goalwin, Properties of cavity walls, NBS Building Materials and Structures Report BMS136 (1953), Superintendent of Documents, Washington 25, D. C. 15A.

[30] D. G. R. Bonnell and W. R. Pippard, Some common defects in brickwork,

National Building Studies Bulletin No. 9, Department of Scientific and

Industrial Research, Building Research Station, London (1950).

38
in

1] F. O. Anderegg, Efflorescence, ASTM Bulletin No. 185, 39 (Oct. 1952). TP155.

||2] L. A. Palmer and D. A. Parsons, Permeability tests of 8-inch wallettes, Proc. ASTM 34, part II, 419 (1934).

13] Standard methods of sampling and testing brick (initial rate of absorption

(suction)), ASTM Book of Standards, part 3, p. 419 (1952).

,4] J. W. McBurnev, M. A. Copeland, and R. C. Brink, Permeability of brick- mortar assemblages, Proc. ASTM 46, 1333 (1946).

15] R. E. Copeland and C. C. Carlson, Tests of resistance to rain penetration

of walls built of masonry and concrete, J. Am. Concrete Inst. 11, 2, 161—

192 (Nov. 1939).

i6] Joseph A. Wise, Water permeability of structural clay tile facing walls, Bulletin No. 27, Univ. of Minn. Institute of Technologv, Engineering

Experiment Station, 51, 36, (Aug. 18, 1948). C. C. Fishburn and D. E. Parsons, Tests of cement-water paints and other waterproofings for unit-masonry walls. NBS Building Materials and

Structures Report BMS95 (1943). Superintendent of Documents, Washington 25, D. C. 25^

38] K. C. Tippv, Good practice in concrete masonrv wall construction. J. Am.

Concrete" Inst. 13, 4, 317-28 (Feb. 1942). The discussion is printed in Nov. 1942 Supplement.

39] F. E. Richart and N. M. Newmark, The strength of monolithic concrete

walls, University of Illinois Bui. 277 (1935).

0] A. E. Seddon, The strength of thin walls in axial compression under dis- tributed loading, Intl. Assn. for Bridge and Structural Engineering, Liege

Congress 1948 Final Report, p. 589.

41] Norman Davey, Research in Great Britain on the performance of burnt Iclav products in structures, and its influence on practice, Bldg. Research

Cong., Div. 2, p. 50 (1951) London.

42] C. C. Fishburn, Prevention of dampness in basements, J. Am. Concrete

Inst. 19, 6, 421-36 (Feb. 1948).

43] H. L. Whittemore, A. H. Stang, and C. C. Fishburn, Structural properties

of a reinforced-brick-wall construction and a brick-tile cavity-wall construction, NBS Building Materials and Structures Report, BMS24 (1939), Superintendent of Documents, Washington 25, D. C. 15<£ 44] Anchorage of factory roofs, together with Supplement, Anchoring board-onjoist roofs, Associated Factory Mutual Fire Insurance Cos., Inspection

Dept., 184 High St., Boston 10, Mass, Loss Prevention Bulletin No. 7.13

(Sept. 1947)

.

45] H. A. Sweet, Resistance of brick walls to wind, Eng. News-Record, 131,

p. 630-631 (Oct. 21, 1943).

46] J. W. McBurnev and A. R. Eberle, Further study of water penetrability of clay and shale building brick, Am. Ceram. Soc. 17, (5), 210-216 (1938).

| Washington, December 22, 1953.

39

U. S. GOVERNMENT PRINTING OFFICE: 1954
6 9 9

1