Masonry Magazine January 1977 Page.21
7.6. Hollow Walls (Cavity and Masonry Bonded)
# 7.6.1. Cavity Walls
The facing and backing of cavity walls shall be bonded with 1/4-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 4½ square feet of wall area. Ties in alternate courses shall be staggered as indicated in Section 7.1.2, 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 corrosion-resistant metal, or other approved protective coating.
# 7.6.2. Masonry-bonded Hollow Walls
Masonry bonded hollow walls shall be bonded as required in Section 7.1.1. Bonding with Bonders (Headers).
GROUTED MASONRY
Grouted masonry is defined in the A41.1 Standard: "1.6.13. Grouted Masonry. Grouted masonry is masonry in which the interior joints are filled by pouring grout therein as the work progresses." Major construction provisions for grouted masonry contained in Section 8 of the A41.1 Standard require: (1) all masonry units in the outer wythes to be laid in M or S mortar; (2) all interior joints to be filled with grout; and (3) grouted longitudinal vertical joints to be not less than ¾-in. wide.
In actual practice, since grouted masonry is usually reinforced, grouted masonry is ordinarily designed and constructed to conform with applicable requirements for reinforced masonry contained in the A41.2 Standard or the BIA Standard.
MISCELLANEOUS MASONRY REQUIREMENTS
General
Miscellaneous requirements such as anchoring of walls, chases and recesses, lintels and arches, beams and joist supports, corbelling, and precautions during erection are included in Section 11 of the A41.1 Standard.
# Anchoring of Walls
In Section 11.1, the A41.1 Standard requires meeting or intersecting walls to be masonry bonded or adequately anchored, if depended upon for lateral support. Also, the ends of joists, beams and other structural members bearing on, framing into or supported by masonry walls must be adequately anchored.
# Chases and Recesses
General limitations for chases and recesses in masonry walls (Section 11.2.1) include: (1) a maximum depth of ⅓ the wall thickness; (2) a maximum horizontal length of 4 ft; (3) a minimum masonry thickness of 8 in. in back of chases or recesses (or between adjacent chases and recesses); and (4) a maximum aggregate area of chases and recesses in any wall equal to ¼ the whole area of the face of the wall in any story. In residential buildings not over 2 stories in height, vertical chases in 8-in. walls may be 4-in. deep and up to 4 sq ft in area, if they are built-in.
# Lintels and Arches
A minimum bearing length of 4 in. is required for lintels and arches. Maximum lintel deflection can not exceed 1/360 the clear span. (Section 11.3).
# Beams and Joist Supports
Minimum bearing for beams and girders is required to be at least 3 in. in actual length upon solid masonry not less than 4 in. in depth. For joists, the depth of the solid masonry bearing course may be reduced to 2¼ in. (Section 11.4).
# Corbelling
11.5.1. Maximum Projection. Except for chimneys, the maximum corbelled horizontal projection beyond the face of the wall shall be not more than ½ the wall thickness and the maximum projection of one unit shall neither exceed ½ the depth of the unit nor ⅕ its width at right angles to the face which is offset.
# Precautions During Erection
Section 11.9 contains requirements concerning the bracing of walls during erection, wetting of brick, and protection against freezing.
SUMMARY
As indicated in the Introduction of this Technical Notes, empirical design procedures, as contained in American National Standard A41.1-1953, are still valid and accepted procedures for the design of non- reinforced brick masonry. The use of such procedures in the design of bearing walls in low-rise buildings and other applications is widespread. For building applications requiring a more detailed and rational structural analysis, such as load-bearing wall buildings exceeding four stories in height, it is suggested that designers consult and follow the procedures contained in the BIA Standard for Engineered Brick Masonry.