Photos courtesy New York City Brickwork Design Center
Movements in the brick veneer
Brick veneer normally experiences moisture expansion and thermal expansion/contraction, which is absorbed by its expansion joints. (Expansion joints are used for clay brick masonry walls, which expand, and should be filled with compressible material. Concrete masonry, however, typically experiences contraction, and should be designed with the inclusion of control joints filled with premolded materials.) The horizontal expansion joints in the brick veneer should be located at the continuous steel shelf angles at every floor level.
Brick veneer at the typical apartment building wall is approximately 3 m (10 ft) high per floor, and the moisture expansion of this brick veneer could be calculated with the Brick Industry Association (BIA) formula:
0.0005 x L
= 0.0005 x 10 ft x 12 in.
= 0.06 in.
This is approximately 1.5 mm (1/16 in.) per floor.
The moisture expansion behavior of the clay brick depends primarily on the raw materials and secondarily on the firing temperatures—the specifics are beyond this article’s scope. Such expansion is an irreversible process, primarily taking place during the first months, but continuing at a much lower rate for several years.
In addition to moisture expansion, brick veneer undergoes thermal expansion. Walls with dark-colored brick and southern exposure could have temperatures at the brick face of approximately 57 to 60 C (135 to 140 F) in the summer. The winter temperature of the brick veneer could fall below the freezing point to –12 C (10 F) in other locations, such as New York City. The vertical thermal expansion of this brick veneer one floor high could be calculated with this BIA formula:
0.000004 x (Tmax − Tmin) x L
= 0.000004 x (140−10) x 10 ft x 12 in.
= 0.0624 in.
This is approximately 1.5 mm (1/16 in.) per floor.
The total maximum vertical expansion of 3-m high brick veneer (W) could be:
1/16 in. + 1/16 in.
= 1/8 in.
Brick veneer evenly expands up from the support at the continuous shelf angle located at every floor level, but the shelf angle moves down with the CMU bond beam to which the angle connects.
Vertical expansion joints in the brick veneer should be located at each side of the exterior corners within 1.5 m (5 ft) of the corner, and then at 7 m (25 ft) apart, in accordance with BIA recommendations. The most economical location of the brick veneer vertical expansion joints would be at the window jambs (with a continuous shelf angle located at each floor window head level), because there is a soft joint between the window frame and the brick veneer window jamb anyway. The expansion joint should be provided within the brick veneer spandrel panel only.
