NATIONAL BUREAU OF STANDARDS REPORT

21+62

REQUIREMENTS FOR

CONCRETE- MASONRY CONSTRUCTION

toy The Staff of

The Building Technology Division

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
U. S. DEPARTMENT OF COMMERCE

Sinclair Weeks, Secretary

NATIONAL BUREAU OF STANDARDS

A. V. Astin, Director THE NATIONAL BUREAU OF STANDARDS

The scope of activities of the National Bureau of Standards is suggested in the following listing of

the divisions and sections engaged in technical work. In general, each section is engaged in specialized research, development, and engineering in the field indicated by its title. A brief description

of the activities, and of the resultant reports and publications, appears on the inside of the back

cover of this report.

Electricity. Resistance Measurements. Inductance and Capacitance. Electrical Instruments. Magnetic Measurements. Applied Electricity. Electrochemistry.

Optics and Metrology. Photometry and Colorimetry. Optical Instruments. Photographic

Technology. Length. Gage.

Heat and Power. Temperature Measurements. Thermodynamics. Cryogenics. Engines and

Lubrication. Engine Fuels. Cryogenic Engineering.

Atomic and Radiation Physics. Spectroscopy. Radiometry. Mass Spectrometry. Solid State

Physics. Electron Physics. Atomic Physics. Neutron Measurements. Infrared Spectroscopy.

Nuclear Physics. Radioactivity. X-Rays. Betatron. Nucleonic Instrumentation. Radiological Equipment. Atomic Energy Commission Instruments Branch.

Chemistry. Organic Coatings. Surface Chemistry. Organic Chemistry. Analytical Chemistry.

Inorganic Chemistry. Electrodeposition. Gas Chemistry. Physical Chemistry. Thermochemistry. Spectrochemistry. Pure Substances.

Mechanics. Sound. Mechanical Instruments. Aerodynamics. Engineering Mechanics. Hydraulics. Mass. Capacity, Density, and Fluid Meters. Organic and Fibrous Materials. Rubber. Textiles. Paper. Leather. Testing and Specifications. Polymer Structure. Organic Plastics. Dental Research.

Metallurgy. Thermal Metallurgy. Chemical Metallurgy. Mechanical Metallurgy. Corrosion.

Mineral Products. Porcelain and Pottery. Glass. Refractories. Enameled Metals. Concreting Materials. Constitution and Microstructure. Chemistry of Mineral Products.

Building Technology. Structural Engineering. Fire Protection. Heating and Air Conditioning. Floor, Roof, and Wall Coverings. Codes and Specifications.

Applied Mathematics. Numerical Analysis. Computation. Statistical Engineering. Machine

Development.

Electronics. Engineering Electronics. Electron Tubes. Electronic Computers. Electronic

Instrumentation.

Radio Propagation. Upper Atmosphere Research. Ionospheric Research. Regular Propagation Services. Frequency Utilization Research. Tropospheric Propagation Research. High

Frequency Standards. Microwave Standards.

Ordnance Development. These three divisions are engaged in a broad program of research

Electromechanical Ordnance, and development in advanced ordnance. Activities include

Ordnance Electronics. basic and applied research, engineering, pilot production, field testing, and evaluation of a wide variety of ordnance materiel. Special skills and facilities of other

NBS divisions also contribute to this program. The activity is sponsored by the Department of

Defense.

Missile Development. Missile research and development: engineering, dynamics, intelligence,

instmmentation, evaluation. Combustion in jet engines. These activities are sponsored by the

Department of Defense. • Office of Basic Instrumentation • Office of Weights and Measures.
NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT NBS REPORT

IOOO-IO-I4.716 April 23, 1953 21+62

REQUIREMENTS FOR

C ONCRETE- MASONRY C OBSTRUCTION

This report has been prepared at the

request of the Engineering Division, Military

Construction, Office, Chief of Engineers, for

use as a chapter In the OCE Engineering Manual

on Military Construction.

The publication, repriri

unless permission is obi

25, D, C, Such perntls

cally prepared If that

Approved for public release by the ia,t ’ ls P rohlbl,ed Director of the National Institute of

ards ' Washlneton

Standards and Technology (NIST)

has ^

0n speclfl 0

v 7

t for Its own use, on October 9, 2015.

1 0 SCOPE . The instructions in this chapter contain

design and construction procedures for walls and partitions

of concrete-masonry units® Its purpose is to inform Corps

of Engineers personnel and consulting architect-engineers of

criteria to be followed in the preparation of working drawings

and specifications for military construction. It also contains background material. This chapter is not concerned

with floors, roofs, or other constructions not involving the

use of masonry units® The "American Standard Building Code

Requirements for Masonry" (ASA ALpl . l-19i|4 ) a-nd 1953 revision

(see par. 13a), hereinafter referred to as "Alql.l", is the

basis of masonry-construction design, and applicable sections

may be used in conjunction with this publication except as

modified herein® Other codes and specifications referring

to subjects discussed herein are listed in paragraph 13

2* CONCRETE-MASONRY UNITS ® Concrete -masonry units as

used in this manual include: hollow load-bearing concrete

block, solid load-bearing concrete block, non-load-bearing

concrete block, and concrete brick. The units may be used

for exterior and interior load- bearing and. non-load-be aring

walls, partitions and fire walls, backing for brick or other

facing, fireproofing over metal structural members, piers,

retaining walls, and chimneys. A "concretemasonry unit" is defined as a building unit made from cement

and suitable aggregates such as sand, gravel, crushed stone,

cinders, burned clay or shale, or blast-furnace slag. A

"hollow-masonry unit" is defined as a masonry unit whose net

cross-sectional area in any plane parallel to the bearing

surface is equal to or less than 75 percent of its gross

cross-sectional area measured in the same plane. A solid

concrete masonry unit is a. masonry unit whose net crosssectional area of concrete in all planes parallel to the

bearing surfaces are more than 75 percent of its gross crosssectional area measured in the same planes. The moisture

content of concrete units gives a rough measure of the tendency of the construction to crack as the result of the drying

and shrinkage of the units. Concrete shrinks with the loss

of moisture while drying to an air-dry condition,, When moist

units are placed in a wall and the wall Is restrained, tensile

and shearing stresses are developed as the units dry® These

stresses may cause unsightly cracks in the wall,

2a. Concrete-masonry units should conform to the OCE

Guide Specification CE-206.01 (par. 13b). The requirements

of CE-206.01 should h ave preference over those contained in

other specifications and standards for concrete -masonry units

mentioned herein®
2

2b. Load-bearing and non-load-bearing hollow-masonry

units should conform to the following requirements of Federal

Specification 3S-C-621 (see par. 13c) for compressive strength:

For load-bearing units, if the thickness of the outer shell

parallel to the exposed surface of the wall is 1 l/lq in, or

more, the required minimum average compressive strength for

the five units tested shall be 700 lb/in2 of gross area, the

minimum for individual blocks 600 lb /in2

. If the thickness

of the shells is 3/4 in. to, but not including, 1 i/4 in.,

the minimum average shall be 1000 lb/in2 of gross area and

the individual minimum 800 lb/in2

. As the compressive strength

of masonry walls Is approximately proportional to the thickness

of the bearing shells, greater strength for the units with thin

than with thick shells is required so that the compressive

strength of the masonry walls of thin-shelled units will not

be less than required. The following exception will be made:

Concrete block used in exterior walls below grade, not parged,

and subject to frost action, shall have a minimum average compressive strength of 1000 lb/in2 of gross area for the average

of five units tested, and a minimum compressive strength of

800 lb/in2 for individual units regardless of the shell thickness,, The average compressive strength of non-load-bearing

units shall be at least 380 lb/in2

.

2c. The compressive strength of solid load-bearing

concrete-masonry units shall conform with the requirements

of ASTM Standard C 145”40 (see par. 13d).

2d. The compressive strength of concrete building brick

should meet the requirements of Federal Specification 33-B-663

(see par. 13e). For Grade A brick, these requirements ere not

loss than 2500 lb/in2 for the average of five bricks and not

less than 2000 lb/in 2 for individual bricks j for Grade B

brick not less than 1250 lb/in2 for the average of five bricks

and not less than 1000 lb/in”0 for individual bricks.

2e . Hollow and solid concrete-masonry units intended for

use in fire-resistant walls should meet the requirements of

Underwriters Laboratories "Standard for Concrete Masonry Units"

(see par. 13f).

2f. For load-bearing units exposed to soil or weather,

the absorption shall not exceed 16 lb/ft 3

.

2g. The average moisture content in the units at the time

of laying should not exceed 30$ of the total absorption of the

units (see par. 13b). Whore such blocks may be difficult to

obtain because of high humidity In a locality, the Contracting

Officer may revise this requirement to allow not more than 35%

moisture content subject to the approval of the Chief of

Engineers

.
- 3

-

2h. Units must be protected from rain and kept dry prior

to laying. Units should be stacked in such a way that air

circulation may occur, thus facilitating drying; no units

should bo placed directly on the ground while being stored. The

contractor will be held responsible for providing and maintaining tho protection necessary to prevent rewetting of delivered units prior to their use* Units which fail to moot

tho moisture-content limitation should bo sot aside for further

drying and should not be used until retested and proved satisfactory. Unprotected units which have been wetted should be

considered too wet to use unless they have been shown by tost

to be adequately dry e

2i. Units should be of the same manufacture and composition for oach building, unless otherwise approved by the Contracting Officers Units made by more than one manufacturer

for use in the same building, when permitted, should bo of

similar composition, sizo, and appearance. All units should

be sound and free from cracks or other defects which would

interfere with proper setting of tho units or impair tho strength,

appearance, or durability of tho construction.

2 j . Masonry shall be protected against freezing for at

least ]p 8 hours fifter being laid. No masonry should be built

on frozen material. No masonry units should bo laid when the

air temperature is loss than )pO

u F unless the temperature is

rising, and no units shall in any case bo laid when tho outdoor temperature is below 35° F unless provisions are made to

maintain the masonry at a temperature above L|_ 0

° F for at least

I4.8 hours (see par. 10c).

3. MORTAR . To obtain masonry joints of high quality with

ordinary construction methods, an intimate and complete contact

of tho mortar with the surface of tho masonry unit is necessary.

Although the skill and the amount of effort exerted by the. mason

affect the quality of the joints in masonry, tho quality and the

condition of the materials aro the important factors. Mortars

which have low water rctent ivit ie s tend to stiffen so rapidly

when in contact with tho surface of an absorptive masonry unit

that they become too dry and stiff to permit on intimate and

complete contact of the mortar when tho second unit is pressed

against it. Also, mortars of low water retentivity tend to

"bleed” if allowed to stand. The wetness (f lowability ) of the

mortar being used by tho mason has an important influence on

the extent and intimacy of tho bond between the mortar and the

units; the wetter the mortar the more complete and the stronger

tho bond between mortar and unit and the more watertight the joint.
- 4 -

3a„ Mortar materials and proportioning should comply with

the requirements of the OCE Guide Specification CE-207 (soe

par. 13h) and Federal Specification SS-C-l8lb (see par. 13i).

3b. Water used in mixing mortar should be clean and free

from acids, alkalis, and organic materials 0 Sand should conform to the requirements of the ASTM Specification C144 (see

par. 13 j) « Sands deficient in fines generally produce harsh

mortars, difficult to handle. Fine sands that are deficient

in the coarser properties give mortars that may shrink

excessively.

3c. Mortar used

fied as follows:

Type

in masonry construction will bo classiAvorage compressive strength

of three 2- inch cube s lb/in2

A-l ........ 2500

B, B-l 750

C, C-l 350

See par. 12f

3d. Mortars of the following proportions may be assumed

to meet the strength classification:

Proportions by volume

Hydrated lime Aggregate measure

Mort ar or lime putty in a damp and

type Cement allowable range loose condition

A-l 1 (port land) .

i/U 3

B ..... . 1 ( Portland) .

2/3 to 1 1/4. . .5 to 6

B-l ... . 1 (masonry )Z a . . 2.5 to 3

C. 1 (portland) .

2 to 2 1/2. ....

7.5 to 9

C-l 1 (masonry ) /b . . 2.5 to 3

/a Type Ii Masonry Cement, ASTM C91 _ 5l.

/b Type I Masonry Cement, ASTM C91-51.

3e . Mortar should have a flow after suction of not less

than 70/ of that immediately before suction.
- 5

-

3f . Mortars which have stiffened because of chemical

reactions associated with hardening should not be used, but

those which have stiffened because of the loss of mixing water

through evaporation should be retempered to restore their workability. Water should bo added as frequently as needed. In

general, masons should be encouraged to use as much mixing

water as possible without impairing the workability of the mortar

3g® The standard thickness of mortar joints for both horizontal and vertical joints should be 3/8 In. The horizontal

and vertical ends of the shells of the units that are parallel

with the faces of the wall shall be covered with mortar, and

the spaces between these shells 'and those of adjacent units

shall be filled completely. Mortar shall not be placed on the

ends of the interior webs of the units. Mortar joints on the

weather side of exterior walls should be thoroughly compacted

and pressed tight against the edge of the units wr ith a proper

tool to provide a concave or V-shaped joint.

3h. Masonry may be laid in type A-l, B, B--1, C, or C-l

mortar, with the following exception: Type C and C-l mortajr

should not be used In isolated piers or load-bearing or exterior walls of hollow-masonry units,

4* STRUCTURAL DESIGN. Contracting Officers and contractors are referred t o Alq 1 . 1 for a more detailed discussion of

some of the phases of structural design using concrete-masonry

units

[j.a. The allowable compressive stresses in pounds per

square inch of gross cross-sectional proa should not exceed

the following amounts:

Brick and other solid units of sand-limo or concrete

Aver age c ornp r e s s I ve

strength of units/fL

lb/in E

2500 to 4500 .........

1500 to 2500 ...

/a Tested in the position used

Mortar type

a-T b, B-l C, C-l

lb/in^ Ib/in^ lb /inf

175

125

i n the mas onry

llj.0

ICO

110

75
Solid concrete -masonry units

Mortar type

- 6 -

Hollow-masonry units

Grade A-l B, B-l C, 0-1

lb/in~ lb /in2 lb/in*'

A. . . . 175 125 80

B . . . . 125 100 60

Unit

.Mortar type

A-l B, 3-1

lb /in2 * lb /in2 * Hollow units 85 70

-•gross area

In walls composed of different kinds or grades of units or

mortar, the maximum stress shall not exceed the allowable

stress for the weakest combination of unit and mortar of which

the assembly is composed.

4-b . Walls of hollow-masonry units not designed as reinforced masonry should be supported at right angles to the wall

face at Intervals not exceeding 18 times the nominal wall

thickness o Solid-masonry walls should be supported at right

angles to the wall face at Intervals not exceeding 20 times

the nominal wall thickness. Lateral supports may be defined

as the vertical and horizontal members of a structural frame

in contact with the wall, including floors and roofs intersecting a load-bearing wall, pilasters, and columns or struts

supporting roofs. If the limiting distance for support Is

selected horizontally, then no limits are set for the distance

between floors. If the limiting support distance is vertical,

that is if the floors and roof serve as the lateral support

and are placed closer together than tho limiting distance,

cross walls or other vertical members which provide lateral

support are not required. Sufficient bonding or anchorage

shall be provided between the walls and the supports to resist

the assumed lateral load.

Ipc . The minimum nominal thickness of masonry bearing

walls not exceeding 12 ft in height should be at least 8 in.;

where the height exceeds 12 ft but does not exceed 35 ft,

walls should be 12 in. thick.
7

i|d. Non-load-bearing exterior walls and walls enclosing

stairways, elevator shafts, penthouses, or bulkheads may not

be less than 8 in. thick.

l|_e • The vertical or the horizontal distance between

lateral supports of non-load-bearing partitions should not

exceed 36 times the thickness of the partition, including

plaster. For non-load-bearing wails that are not plastered,

the unsupported length or height, whichever is the smaller,

should not exceed the following:

Nominal Maximum distance

wall thi ckness between later al supports

in. ft

k ....... . 12

6 . . 18

3 2 !+

-X. 12£— • 4 O • 1 • 9 36j

4f . Fire walls shall have a thickness not less than

that required to provide the needed fire resistance rating

and should be built of suitable units (see pars, 2e and 1 3f )

The maximum distance between lateral supports of fire walls

should not exceed 20 times the wall thickness, including plaster.

5. CONTROL OF SHRINKAGE CRACKS. Shrinkage cracks in

concrete masonry may be controlled by the use of bond beams,

joint reinforcement, and control joints. The steel bars and

wires in bond beams and in joint reinforcement are depended

upon to greatly reduce the width (but pcssibl}?- increase the

number) of shrinkage cracks in the masonry. Control joints,

in effect, limit the length of a wall and thereby tend to

reduce the tensile stresses which cause the shrinkage cracks.

The amount of drying shrinkage which may be expected from a concrete-masonry unit depends upon its composition, method of

manufacture, and the amount of moisture that it loses after

being laid in the masonry. (Measures for controlling the

moisture content of the units are given in pars. 2d and h.

In order to correlate the potential shrinkage of the units

with the necessary preventative measures for the control of

cracking, the units are divided into the following two groups:
8

Drying shrinkage grouping of concrete -masonry units

Kind of

masonry unit

Weight of

concrete

Max imum line ar shr Ink age » Gr oup 1 Gr oup 2

lb/ft 3 percent percent

Sand- lime and 125 or more no limit 0.03 or less

concrete bricks

Hollow or solid 100 or more no limit 0. 0.1|_ or less

concrete block

Hollow or solid Less than 100 no limit 0.05 or less

concrete block

-See par. 12b for method of testing.

5a. Bond beams should consist of at least two No. l\. steel

bars or the equivalent in cross-sectional area set in bondbeam (open-top) block filled with concrete. The bars should

conform to the requirements of AoTK A305“4-9 (see par. 130,

and the concrete should be Class B 2500 lb /in'5 concrete conforming with the requirements of OCE Guido Specifications forConcrete, CE~20fp (see par. 13m). When the concrete in the

bond-beam unit is deeper than 7 in., half as much reinforcement will be added at the top of the beam as is required in

the bottom. Tvpical bond-beam units are shown in figure 1.

5b. Bond beams should bo placed in the top courses of

all concrete-masonry foundation walls and near the top courses

of all load-bearing walls built of concrete-masonry units,

preferably above the highest opening. Bond beams should form

a continuous, horizontal, reinforced concrete bolt connecting

and capping all intersecting load-bearing walls. The bond

beams should be continuous across control joints; but dummy

joints, corresponding in. location with control joints, may

be placed in them. Bond-beam units -"nd reinforcement may be

used as lintels over door and window openings instce,d of

poured or precast concrete lintels. Bond beams are not required in interior non-load-bearing walls. Bond-beam requirements are given in the table in- paragraph 7b.

6. JOINT REINFOR C EMENT . Joint reinforcement may consist

of 3/l6-in (No. If gage ) parallel wires with l/8-in. (No. 9 gage)

welded cross ties or j/l6-in. horizontally trussed parallel

wires. The cross wires should be placed at intervals not

exceeding 6 in. for smooth, longitudinal wire, and at intervals
9

not exceeding 16 in. for deformed wire. The cross wires or

trussed webbing should preferably be woldod to the longitudinal

wires in the same plane as the longitudinal wires and without

crossing or lapping them. The longitudinal reinforcing wires

should be of a cold- dr awn steel conforming to ASTM Standard

A82-311 (soo par. 13n) except that the tensile strength should

bo at least 100,000 lb/in2

. The joint reinforcement should

bo made flat, not coiled* When laid in the joint, the longitudinal wires, at splices, should be lapped at least 32 diameters and should be bent and lapped at corners of tho wall.

Tho laps in straight lengths 'may be made by bending the longitudinal wires inward at one end of a section. See figure 2

for methods of using joint reinforcement. Joint reinforcement should bo terminated at each side of a control joint.

Typical reinforcement requirements of a non-boaring wall

construction are shown in figure 3.

6a. Joint reinforcement should be placed mound openings

where high tensile stresses are usually developed. All walls

containing openings and built of Group 1 units should contain

joint reinforcement in the first bed joint over a lintel and

in the first two bed joints under a sill* Walls containing

openings and built of Group 2 units should have joint reinforcement in the first bed joint beneath a sill*

6b. Additional requirements for joint reinforcement are

listed in the table in paragraph 7b.

6c. Where joint reinforcement is used, the minimum thickness of the shells of units shall be 1 1 /Ip in.

6d. Vertical, reinforced concrete studs tied into the

footing and the bond beams shall be required in earthquake

and hurricane regions at the corners of buildings or at

regular intervals. Reinforced concrete frames may bo used

at large openings. Reinforcement should consist of at loast

one Wo. bar or the equivalent cross-scctional aroa.

7. CONTROL JO HIT S. Control joints divide a masonry

wall into longitudinal segments, thereby minimizing the tendency for shrinkage cracks to occur. They provide a continuous

vertical separation between bond beams through the entire

thickness of the wall, including any facing or rigid finishes.

The joints may be masked by the use of pilaster blocks and

column faces. Preference should be given to control joints

which provide for the possible transfer of lateral loads across

the joint. Control joints should be used above expansion joints

in monolithic concrete foundation walls, at junctions in L-
10

T-, or U-shaped buildings, at jogs or offsets if the wall on

either side is more than 10-ft long, at abrupt changes in wall

height and thickness along a lateral plane, and at the intervals specified below. Control joints should be filled with

light-colored plastic calking compound and are illustrated

in figures l\., 5, 6, and 7*

7a. No control joints are required in walls of Group 2

units except over expansion joints in monolithic concrete

foundations

.

7b x A summation of the requirements for bond beams,

joint reinforcement, and control joints is given in the

following table:

*
- 11

Summary of Bend-Ieam, Joint Reinforcement, and Crntrrl Joint Requirements

for Concrete Masonry Uni us

Kind Type of wall

of unit

Group 1

1 Rxterior and

' interior load-

’ bearing walls

Group 1

Group 2

Group 2

Exterior and

interior nonload -bearing

walls

Exterior and

ixitcrior loadbearing walls

Exterior and

int- rior non- load-bearing

walls

Bond beams

Option 1 ' at intervals of 10 ft in neight (but

' net between openings) , including bond

1 beams just above concrete masonry

1 foundation wails and near the top of

1 walls.

Joint reinforcement Control joints

In first two joints beneatn

sills and the first joint over lintels.

Above expansion joints in foundation walls, and at wall junctions,

offsets, and changes in wall

height or thickness.

Option 2 Just above concrete masonry foundation

vails and near top of wall (just

above nignest opening.)

r

At intervals not exceeding

16 in. vertically, including the first two joints

beneath sills and the first

joint over lintels.

Same as Option 1, above.

Option 3 Same as Option 2, above.

Option 1 None (except that be low-grade walls

should ne topped by a bond beam.)

Same as Option 1, above. At intervals not exceeding 15 ft,

including joints in the places

specified in Option 1, above.

Same as Option 2, above. Same as Option 1, above.

Option 2 None (except that below-grade wails

should be topped by a bond beam.)

Just above concrete masonry foundation

walls and near top of wail (just above

highest opening.)

None (except that below-grade walls

should be topped by a bond beam.)

I n the first two bed joints

beneath sills, and in the

first bed joint over lintels

At intervals of 15 ft of wall length,

including control joints above expansion joints in foundation vall9,

at wall junctions, offsets, and

changes in wall height or thickness.

In the first joint under a

sill.

Same as Option 1, above.

In the first joint under a

sill.

None.
I

I

I
12

8. CONSTRUC TION DETAILS . Method's of bonding walls shall

bo as shown In figures -

5, 9, and 10.

8a. Concrete floor or roof slabs cast on the tops of

walls provide sufficient attachment to the walls so that additional anchorage is not required. Provision should be made

to reduce tho lateral forces exerted at the top of concrete

masonry bearing walls by the expansion and contraction of

cast-in-place roof slabs. The top of the bond-beam course,

when used, shall be s creeds d, covered with a thin bed of mortar

that is carefully troweled to a smooth surface, parallel with

the plane of the under side of the roof slab. After the

troweled surface has hardened, and before placing the roof

slab, the surface daq.,11 be covered with smooth-surfaced asphalt

roll roofing 58-lb grade conforming wnth the requirements of

ASTM Standard D22!p_ 50T (see par. 13o). This method of construction Is shown in figure 1,3.

8b. The supporting joints of wood and of other lightweight roofs should be anchored to the masonry by 5/8- In.

diameter, steel bolts having a minimum length of anchorage

of 6 in, in the bond beam and spaced on Ip- ft centers. The

construction for a wood roof Is also shown in figure 13.

8c. Lintels over door or window openings shall be designed to support the full weight of the masonry above plus

the imposed load on the wall. They may be formed of reinforced bond-beam units filled with Class B concrete and should

bear on the wall at each end not loss than l/iOth of the span

but at least 8 In.

8d, Window sills may be precast or ca st-in-place . Window and door framing details are shown in figures 11 and 12.

8e , Flashing should be provided at projecting trim,

under vertical joints in sills, and over windows. The flashing should conform with the requirements of Guide Specification CE-220.03 (see par. 13t )

8fMethods of handling joint reinforcement at corners

shall be as shown In figure 2.

8g. Methods of handling Intersections of wlls with

columns are shown in figure lip.

8h„ Weep holes in panel walls of frame structures shall

be constructed as shown in figure l5.
13

9. M0DULAR DESIGN . To the extent consistent with other

requirements, masonry wall heights and lengths, sill and

lintel heights, location and size of openings, and related

architectural and constructur al features should be dimensionally coordinated so as to minimize cutting of masonry units

or the use of special fractional-size units. Modular design,

based on an 8-in. module, is preferred. Mortar joints should

be 3/8 in., so that a nominal 8 by 8 by 16-in. unit, for

instance, would have an actual width of 7 5/8 in., a height

of 7 5/8 in. , and a length of 15 5/8 in.

9a. In modular design, all window and door frames will

be of dimensions which are multiples of modular full or halfsize units. It is preferable to locate window heads and

doors in a horizonta.1 line coinciding with the under side of

a bond beam, thus eliminating separate lintels. For an 8 by

8 by 16-in. full block, for instance, both horizontal and

vertical dimensions of openings should be multiples of 8 in.

Where the sizes of local units differ from this, the module

sizes should be adjusted accordingly. In modular design,

the dimensions shown in working drawings are nominal and are

from, center to center of mortar joints. The designer should

ascertain the availability of blocks conforming with the

shrinkage requirements for the two block groups and should

determine if blocks of specir.l shapes are available.

10. ERECTION . Weathertight concrete-masonry walls are

obtained by a combination of proper design, the use of good

materials, and good workmanship.

10a. On delivery to the building site, units should be

neatly piled free from contact with the ground, and should be

covered by a tarpaulin or building paper to prevent wetting

of the units prior to use. The mason should cover the top

of the unfinished wall with waterproof paper upon leaving the

job at night or when it rains. The contractor should provide

and maintain the protection necessary to prevent the rewetting

of units prior to use. The dampening of units to reduce suction during laying should be prohibited except in extremely

ar id regions , and then should be undertaken only with the

approval of the Contracting Officer, who may permit slight

dampening of the tops and bottoms of the face shells with a whitewash brush. Units which do not meet the moisture-content

limitation should be set aside for further drying and should

not bo used until retested. Unprotected units which have been

rewetted should bo considered too wet unless shown by test to

be otherwise.
10b. The wetness of the mortar affects the strength and

watertightness of masonry joints. Mortars should have high

water retentivity, and the maximum amount of mixing water

should be used, which is compatible with the consistency needed

by the mason. When mortar has stiffened because of the loss

of mixing water through evaporation, the mortar should be retempered. Water should be added as frequently as needed.

10c. The method of making mortar joints is important

in building a watertight wall. Head joints should be carefully buttered to fill the joints tightly.

lOd. Masonry walls in locations where they may be exposed to high winds are vulnerable to overturning, and during

erection adequate provision should be made to prevent their

being damaged by wind.

lOe . Masonry shall be protected against freezing for at

least I4.8 hours after being laid. Unless adequate precautions

against freezing are taken, no masonry shall be built when

the temperature is below 35 ° F with the temperature rising,

or below [j_0° F with the temperature falling. No frozen

materials shall be built upon.

lOf, A properly laid out story rod should be used for

all construction to insure accuracy of construction. Units

should be cut only when unavoidable; a power saw should be

used for such cutting.

lOg. Reinforcement should be properly placed to insure

complete coverage with mortar.

lOh, Tooling of the joints should be delayed until after

the mortar has begun to stiffen, and the tooling operation

should not expose the joint reinforcement. Joint reinforcement that has been exposed by tooling should be covered with

mortar. All cracks and openings in the wall face should be

filled with mortar to the depth of the face shells.

101. At the conclusion of' the masonry work, all mortar

projecting from the wall faces should be cut away with a putty knife or other tool, and all scaffolding, equipment,

surplus materials, and debris should be removed.

11. PAINTING- . Portland cement -water paints or grouts

shall be used as base coats on the exterior faces of all

above-grade concrete-masonry walls that are to be painted.

The grouts shall be used on rough-textured masonry surfaces,
and the paints shall be used on smooth surfaces. The base

coats may be applied at any suitable time after completion

of the walls. There me certain advantages in favor or early

and of late applications. An early application tends to protect the masonry against saturation by heavy and long continued wind-driven rains, thereby preventing an immediate

moisture expansion and a later shrinkage of the masonry. A

late application tends to seal and fill shrinkage cracks which

have developed in the masonry since its completion. Pneumatically applied coatings of suitable cementitious materials

may be used as alternate base coats instead of portland cement

paints and grouts.

lla. Portland cement grouts used, -as base coats on roughtextured walls shall be cither of the two- kinds listed below:

(1) Job mixed grout containing 1+0 to 50 percent

of either white or gray portland cement and 60 to 50

percent of a suitable sand aggregate. The sand aggregate shall pass a No. 21+ sieve and shall otherwise be

suitable for use as a concrete or masonry mortar aggregate.

(2) A paint meeting the requirements of Federal

Specification TT-P-21, typo II, class B (see par. 13g).

llb. Portland cemont paints used as base coats on smoothtextured walls shall be either of the two kinds listed below:

(1) Either white or gray portland cement.

(2) A paint meeting the requirements of Federal

Specification TT-P-21, type II, class A.

llc. Before applying the base coat, the masonry shall

be clean, and all crocks or openings in the wall facing that

arc larger than l/l6 in. in width or diameter shall be filled

with mortar or grout. The masonry shall have been wetted and

shall be in a damp condition but without water showing on the

surface at the time the base coat is applied. Paints and

grouts shall be applied by vigorous scrubbing with brushes

having stiff-fiber bristles. The base coat shall be cured

by light wetting at least twice per day for two days after

application.

lid. Finish coats shall be of water-cement paint and

shall be applied after the base coat has hardened. The

base coat provides protection against the leakage of

wind-driven rain, and the time of application of the
16 -

finish coats should be selected so that weather conditions

and the dryness of the base coats are suitable for the type

of paint that is used. The finish coats may be expected to

seal fine hairline cracks and crazing in the base coats resulting from further drying of the masonry, and application

of the finish coats may therefore be delayed until such drying may have occurred.

lie. An optional method of applying a ceme titious

base coat in lieu of that specified above may be selected

by the contractor. This consists of coating the surfaces

with a mortar consisting of portland cement, a water-repellent

admixture, and selected aggregates (excluding soft aggregates),

applied pneumatically by spray in one continuous operation to

a minimum thickness of 1/8 in. beyond the nominal face of the

wall. Application shall be by a firm specializing in this

type of coating. Specifications for similar but thicker cementitious facings are -given in ACI Standard 805~5l (see

par . 13s ) .

l lf. Finish coats on interior surfaces may be -either

organic or cement-water paints. Interior surfaces should be

prepared for painting in the same way as exterior surfaces,

llg. Contracting Officers and contractors are referred

to the following publications for the solution of specific

problems of surface preparation, paint handling and storage,

and paint failures:

ACI Standard 6l 6— JLp9 (sec par. 13r)

MBS BMS 105 ’’Paint Manual" (see par. 13u)

NBS BMS 110 "Paints for Exterior Masonry Walls"

(see par. 13v)

12 . SAMPLING AND TESTING .

12a. Except as modified herein, methods of sampling,

testing, and inspecting hollow-masonry units shall be in accordance with Federal Specification 3S--C-621 (see par. 13c),

and methods of sampling, testing, and inspecting concrete

brick shall be in accordance with Federal Specification

SS-B-663 (see par. 13e ) . Prior to acceptance of concretemasonry units, samples will be taken at the manufacturer's

plant and tested In accordance with the above specifications.

12b. The manufacturer shall certify that concretemasonry units delivered to the construction site will be

manufactured, cured, and dried in tho same manner as were
17

the samples on which acceptance was based,, If the manufacturer is forced for any reason to alter the manufacturing,

curing, or drying procedures, he shall submit in advance a written description of the proposed changes to the Contracting Officer.

12c. At least 10 days should be allowed for completion

of the drying shrinkage tests. Ten individual units shall

be selected from each, lot of 10,000 units or fraction thereof

and 20 individual units from each lot of more than 10,000 and

less than 100,000 units. For lots of more than 100,000 units,

10 individual units shall be selected from each 50,000 units

or fraction thereof contained in the lot. Additional specimens may be taken at the discretion of the Contracting Officer.

The units selected for testing shall be of full size and shall

be representative in every respect of those to be used or being used in the construction of the masonry. Units previously

subjected to any of the tests which involve their being subjected to temperatures exceeding l50° F shall not be used in

the drying shrinkage test. At the discretion of the Contracting Officer, bars not less than 2 in. in width and equal in

length to the height of the full-sized units may be cut from

the units selected for use in the drying shrinkage test.

12d. The specimens shall be prepared with suitable

contacts for use in : easuring their changes in length to the

nearest 0.0003 in. They shall then be submerged in water at

73 - 5° F for Jq8 hours, foil owing which the initial length

shall be measured. The specimens shall then be dried in a ventilated oven at 230 ± 5

° F for L|.8 hours, after which they

shall be stored for 214. hours in a vapor-tight container at

73 1 5

° F. Their lengths shall then be remeasured. The

percentage drying shrinkage shall be calculated as

1 0 0 ( length wet - length dry )

length wot

12e . Representative samples shall bo taken from the onsite stockpiles for check of moisture content. Two such checks

will be made per week for each 5000 full-scale blocks. Eachtest will be made on at least three full-scale blocks. The

tests will be performed in accordance with Federal Specification SS-C-621 or SS-B-663, or ASTM Standard Cl[|_5, whichever

is applicable. Units which fail to comply will be rejected

in accordance with the applicable specif icat ions , except that

in the case of rejections based on field tests, the contractor

shall have the option of further drying the units until on

retest they arc shown to comply with tho moisture-content

requirement
18

12f. Mortar’s shall be tested in accordance with ASTI!

C 270 - 51T (see par. 13 k).

12g. Sampling and testing as above will be at the expense of the Government.

12h. The above tests end any other tests required in

determining the acceptability of masonry materials should be

made, insofar as possible, before said materials are incorporated in the structure.

13. REFERENCES . Codes and specifications referred to

above are as follows;

13a. American Standard Building Code Requirements for

Masonry (ASA American Standard AI4.I . l-19lqlq) , National Bureau

of Standards Miscellaneous Publication M174, as revised (1953)

13b. Department of the Army, Corps of Engineers, Guide

Specifications for Masonry, CE-206.01.

13c. Federal Specification for Concrete Units; Masonry,

Hollow, SS-C-621 (1931).

13d. American Society for Testing Materials Standard

Specifications for Solid Load-Bearing Concrete Masonry Units,

C 145- 50.

13e , Federal Specification for Brick; Concrete, Sj-B-663

(1932).

13f . Underwriters' Laboratories, Inc., Standard for

Concrete Masonry Units, Subject 6 l 8 (1949).

13g. Federal Specification for Faints, TT-P-21.

13h. Department of the Army, Corps of Engineers, Guide

Specifications for Mortars, Masonry. CE-206.

13i. Federal Specification for Masonry Cement, 3S-C-l8lb

13 j . American Society for Testing Materials Standard

Specifications for Aggregate for Masonry Mortar, Cl 44" 44-*

13k. American Society for Testing Materials Standard

Specifications for Mortar for Unit Masonry, C270-51T.

13^. American Society for Testing Materials Standard

Specifications for Deformed Bars, A305~49.
19

13m, Department of the Army, Corps of Engineers, Guide

Specifications for Concrete for Building Construction, CE-204.

13n. American Society for Testing Materials Standard

Specifications for Cold-Drawn Steel Wire for Concrete Reinforcement, A82~34-

13o. American Society for Testing Materials Standard

Specifications for Roofing, Asphalt, D224- 50T.

13p • Federal Specification for Cement-Water Paint,

Type II, TT-P-21

13q. Department of the Army, Corps of Engineers, Guide

Specification for Military Construction, Painting, General,

CE-250.

13r. American Concrete Institute Standard, Recommended

Practice for the Application ol Port land- Cement Paint to

Concrete Surfaces, 61.6-49.

13s. American Concrete Institute Standard, Recommended

Practice for the Application of Mortar bn Pneumatic Pressure,

805-51, Title 47-4.8,

13t. Department of the Army, Corps of Engineers, Guide

Specification for Flashing, CE-220.08.

Additional references of interest are as follows;

13u. Paint Manual, National Bureau of Standards Building

Materials and Structures Report BMS105 (1945).

13v. Clara Sentel, Paints for Exterior Masonry Walls,

National Bureau of Standards Building Materials and Structures

Report BMS110 (1947).

13wr . British Standards for Precast Concrete Blocks,

492, 728, and 834 (1944? amended 1946).

13x. K. C. Tippy, Good Practice in Concrete Masonry Wall

Construction, J. of the Arner. Concrete Inst., Vol 13, n. 317

(1942).

13y. R. E. Copeland, The Problem of Shrinkage Cracking,

National Concrete Masonry Association, 38 So. Dearborn St.,

Chicago 3, Illinois (rev 195-1).

13z. Concrete Masonry Handbook (1951), Portland Cement

Association, 33 West Grand Ave .

Chicago 10, Illinois.
LIST OP ORAL I MGS

Pig.

I\

T o.

1. Typical bond-bo an units

2. Plan of joint reinforcement

3. Non-bearing wall construction

I4.. Typical control joint using standard stock stretcher

block and concrete core

5. Typical control joint using standard Stock jamb block

and metal ties

6 . Typical control joint using control joint block

7. Typical control joint using standard stock jamb block

and metal clips and bolts

8 . Wall intersection, exterior wall and interior partition

detail showing wire mesh wall ties

9. Wall intersection showing wire wall ties

10. Intersection of two bearing walls

11. Detail of typical metal door frame in partition

12. Optional types of typical jamb anchors for metal door

frames in interior partition

13. Typical details of roof and wall intersections

lip • Column and wall intersection

15. Non-bearing wall construction detail showing arrangement

of floor slab and weep holes In mortar joint at base

course

16 . Typical wall section at wood floor joists

BOND BEAM BLOCK

BEAW LINTEL BLOCK

.BOND BEAM SLOCKS A

T CORNER

F/G.l TYPICAL BOND BEAM UNITS

BEAM L / NTEL BLOCK

s~ DEFORMED NT 6 (APROY- 3//G ") WIRE A.S.TM /V? 8Z-34

( (7EHSILE STRENGTH / 00,000 PS. I.) WITH LATERALLY

\ EXTENDING WELD - CONNE CTL D T/ES ?F NOT LESS THAN \n?s wire, spaced wot more than fe" apart. £

v- WIRE S HA\JiNG ) i ! ~ D/AMETER3 NUN

| INDENTATIONS -/j ^ LAP AT SPLICE

u iG * J

PLAN ?F JOINT REINFORCEMENT AT CORNERS

NO TES: jo/N'T REIN FOR CEMENT SHALL BE

FURNISHED /W FLAT FORM ONLY.

RE/NFORCEMENT MAY 6£ AS SHOWN

FOR OUTSIDE 4 INSIDE CORNERS,

OPT/OAfA L TYPES OF

JO(NT REINFORCEMENT

TACK WELD

DETAIL THRU WALL

WHERE SPLICE OCCURS

SMOOTH - N? € (APRON. 3/(6 ') W/RE -AST#. A/9 8£-3N

(TENSILE STRENGTH 100,000 F. 3 I.) WITH LATERALLY

EXTENDING WELD - CONNECTED TIES OF NOT LESS THAN

N? 3 WIRE, SPACED Not MORE THAN 6 " APART.

JOINT REINFORCEMENT

WALL THICKNESS

I ! C UT

=f

=L

^

ji: 7\

j_ j! BEND

CUT A ND SEND

FOR CORNER MEMBER

F/G 2 PLAW 9F <70/MT REINFORCEMENT
.
F/G.

3

-

NON

-

BEARING

WALL

CONSTHU

CflON



control

JOINT

£4

'A STEEL rod

^calking

MORTAR

PLAN DETA/L

F/G. £ TYPICAL CONTROL JOINT USING STANDARD

STOCK JAMB SLOCK AND METAL TIES•

-CONTROL SO/NT

•CALK/Ng

'/4

" i> JTEEE ROD

MORTAR

~ ELEVATION -

FIG. 6 ZyPrCAL COATPOL JO/AT US/AG

STANDARD CONTROL JO/NT SLOCK

CONTHO, JOIN

CALKING

MORTAR

- ELEVATION

FIG . 7 TYPICAL CONTROL JOINT USING STANDARD

STOCK JAMB BLOCK AND M£TA L CUPS 6 BOLTS

NUT-'

1/4“BOLT7 J M

/ r- Jt L' /

sf/M' -Z a -3 4

V

CONTROL JOINT-' ’—CALLUN

PLAN DETAIL

VAR./ZS

V

U

-A—

r

% rtf’. Ml~H W£L£>£.P Wt/lE AASAJC AOR, PLASTER.

LATH, GfiLVAL/LCO OR SLACK

Plan

FIG 8. WALL INTERSECTION : ..EXTERIOR WALL & INTERIOR. PARTITION

DETAIL SHOWING VX/RE MESH WALL TIES
I

>

-

.
CONTROL JO'NT

" f STERL ROD

r4 MORTAR

STANDARD STOCK

CORNER SLOCK

- PLANT££L ROD

CONTROL JOINT

MOR TAR

MK/NG

MORTAR

MORTAR

F/G./O INTERSECTION 9f TWO SEARING WALLS.

FIG; n - DcTA/L 9F TYPICAL

IN PAP?FT/OF

MPrAL DOOP PPAMS



D ETAIL _?F_ IN TERSECTION 9F R OOF £ WALL 9F ONE

vS TORY $ TRUC 7

RE VW 77/ BEARING 'WALL 4 WOOD ROOT.

*70/? 7V*/r

roof Slab

JOiNl

(a) TOP 9F bond SPAM TROWELLED

AND WORKED SMOOTH.

(p) ASPHALT ROOFING OR

impregnated FELT

DETAIL EF /ALTERSEOT! ON ?R POOF 4 WALL FF OWE

S TOR Y BEARING WALL STRUCTURE HAVING

CONCRETE ROOF SLAB .

SPANDREL DESJ GN

WITH ROOF BEAM FLUSH

WITH ENTERALAR FACE

CF, WALL. ' NON -BEARiNG WALL

REINFORCED CONCRETE

ROOF SLAB $ BEAM

CONSTRUCTION.

MORTAR EOINT

DETAIL 9F INTERSECTION ?F ROOF 4 WALL

WITH NON- BEARING WALL

TRUCTUR

FJG. 13. TYPICAL DETAILS 9F ROOF £ WALL INTERSECTIONS.

PLAN °F REINFORCED CONCRETE COLUMN

SHOWING DOVETAIL TIE.

PLAN ?F R EINF OPCEO CONCRETE COLUMN

HAVING V-SHAPED DEPRESSIONSFIG. !A - COLUMN AND WALL intersection.



1

F/&. !6 typical WALL SfCriON AT WOOD JOIST FLOOR

THE NATIONAL BUREAU OF STANDARDS

Functions and Activities

The functions of the National Bureau of Standards are set forth in the Act of Congress, March

3, 1901, as amended by Congress in Public Law 619, 1950. These include the development and

maintenance of the national standards of measurement and the provision of means and methods

for making measurements consistent with these standards; the determination of physical constants and properties of materials; the development of methods and instruments for testing materials,

devices, and structures; advisory services to Government Agencies on scientific and technical

problems; invention and development of devices to serve special needs of the Government; and the

development of standard practices, codes, and specifications. The work includes basic and applied

research, development, engineering, instrumentation, testing, evaluation, calibration services, and

various consultation and information services. A major portion of the Bureau’s work is performed

for other Government Agencies, particularly the Department of Defense and the Atomic Energy

Commission. The scope of activities is suggested by the listing of divisions and sections on the

inside of the front cover.

Reports and Publications

The results of the Bureau’s work take the form of either actual equipment and devices or published papers and reports. Reports are issued to the sponsoring agency of a particular project or program. Published papers appear either in the Bureau’s own series of publications or in the

journals of professional and scientific societies. The Bureau itself publishes three monthly periodicals, available from the Government Printing Office: The Journal of Research, which presents

complete papers reporting technical investigations; the Technical News Bulletin, which presents

summary and preliminary reports on work in progress; and Basic Radio Propagation Predictions,

which provides data for determining the best frequencies to use for radio communications throughout

the world. There are also five series of nonperiodical publications: The Applied Mathematics

Series, Circulars, Handbooks, Building Materials and Structures Reports, and Miscellaneous

Publications.

Information on the Bureau’s publications can be found in NBS Circular 460, Publications of

the National Bureau of Standards ($1.00). Information on calibration services and fees can he

found in NBS Circular 483, Testing by the National Bureau of Standards (25 cents). Both are

available from the Government Printing Office. Inquiries regarding the Bureau’s reports and

publications should be addressed to the Office of Scientific Publications, National Bureau of Standards, Washington 25, D. C.