When designed, detailed, and constructed properly, brick veneer anchored to a wood frame back-up provides a high-performance wall system for low-rise residential buildings. Designers, builders, and masonry contractors can avoid problems by consulting two excellent publications published by the Brick Industry Association: "Anchored Brick Veneer Wood Frame Construction," BIA Technical Notes on Brick Construction, 28, and the recently published "Brick Veneer—New Construction," BIA Builder Notes #13.
In anchored brick veneer/wood frame construction, a nominal 3-inch or 4-inch-thick exterior wythe of brick is anchored with metal ties to a wood-frame backing system, with a clear air space of 1 inch of more left between the brick and the wood frame. Anchored brick veneer is designed to carry loads from its own weight only. Thus, the veneer should be securely attached to the backing system but not so bonded that the brick and wood frame back-up exert common action under load. The veneer is supported on the foundation, with the ties and backing system providing lateral support.
The weight of the brick veneer must be transferred through the veneer to the foundation. The BIA recommends that the foundation or the foundation wall supporting a brick veneer be approximately the same thickness as the veneer wall assembly.
Since brick veneer is isolated from the rest of the wall and exposed to exterior temperature extremes, sever weather (SW) grade facing brick conforming to ASTM C 216 should be used in residential brick veneer/wood frame construction. The brick selected, according to BIA, should have an average initial rate of absorption (IRA) of not more than 30 grams per 20 inches2 per minute at the time the units are being laid. Birck having higher IRA values can be used if they are wetted immediately before they are laid, or 3 to 24 hours before their use, which allows moisture to be distributed throughout the units.
Type N mortar should usually be used above grade, while type M mortar should be used below grade. Although Type N mortar is suitable for most brick veneer, Type S mortar is recommended where a high degree of flexural resistance is required and may be required in areas of high seismic activity.
Brick veneer ties must allow vertical and horizontal motion parallel to the plane of the wall but resist tension and compression resulting from forces perpendicular to the plane of the wall. They should be spaced no more than 16 inches apart horizontally and vertically. Corrugated steel ties must be corrosion-resistant and at least 22-gauge, 6 inches long, and 7/8 inch wide. They must penetrate into the mortar joint at least half the thickness of the veneer and have at least 5/8 inch of mortar cover to the exposed face. Wire ties used to tie brick veneer to a wood frame should be a minimum of 9 gauge, fabricated from wire conforming to ASTM A 82 "Specification for Steel Wire, Plain, for Concrete Reinforcement." Plate portions of adjustable wire ties typically are 14-gauge. Wire ties should be embedded a minimum of 5/8 inch into the bed joint from the air space and have at least 5/8 inch of mortar cover to the exposed face.
When properly selected, positioned and installed, flashign and weepholes play a critical role in a brick veneer wall's resistance to moisture penetration. Flashing and weeps should be located above all openings, beneath sills, and above grade at the bottom of the wall.