In the past, model codes required brick veneer to be supported by the foundation. The one-story roof would frame into the masonry wall beginning above the roof line. The lower portion of the masonry wall below the roof line would either be concealed or exposed to the interior. An alternate approach would be to use steel beams spanning between brick piers or steel columns to support the masonry on the upper floors. Both of these solutions are expensive. For that reason, many builders use siding on the second floor.
The 1995 edition of the Council of American Building Officials (CABO) One- and Two-Story Dwelling Code allows exterior masonry veneers weighing less than or equal to 40 psi to be supported on wood construction. The CABO code is referenced in many model building codes. The section of the CABO that references brick veneer supported on wood is 703.7, exception 2.
You must consider several factors. First the brick veneer supported on wood framing will experience greater differential movement than the brick veneer supported on the concrete foundations. The wood support is affected by temperature and moisture movement as well as creep deflection. Because of this, the brick supported on wood must be isolated from the portion of brick supported on concrete foundations. To accomplish this, CABO requires a vertical movement joint between the masonry supported by the concrete foundation and the masonry supported by the wood framing. CABO also limits the deflection of wood supporting brick veneer to 1/600 of the span of the supporting members.
Resistance to water penetration is very critical at the interface between the roof and the bottom of the masonry wall above it. Careful attention must be given to detailing and constructing flashings to prevent water leakage into the roof. The traditional approach to flashing at these interfaces is to use a stepped flashing. Each section of the stepped flashing should consist of a through-wall flashing and a counter flashing. The through-wall flashing section should have sealed end dams on both ends. Upper levels of flashing should overlap lower levels of flashing by at least 4 inches.
The Brick Industry Association, in its Engineering Research Digest titled Support of Exterior Brick Veneer on Wood, suggests three different approaches to supporting masonry on combustible construction. The first is to support the brick veneer by a steel angle that bears directly on roof rafters. The roof rafters must be sized to support the weight of the brick veneer with a deflection less than 1/600 of the span of the supporting member. The steel angle used on top of these supporting members should generally be a minimum 1/4-inch-thick horizontal leg.
The masonry veneer can also bear directly on sheathing material that covers the wood rafters. The BIA recommends that No. 15 asphalt-saturated felt be used between the masonry veneer and the roof sheathing material. Stepped through-wall flashing and counter flashing would be used in the masonry above this point to assure that any water penetrating the masonry drains before it can get to the supporting wood structure.
The third technique is to attach the steel angle directly to the wood studs in the back wall using lag screws. The design of the shelf angle should follow the deflection limitation listed in BIA Technical Note 188. The angle must be able to support the brick veneer with a total deflection limited to the lesser of 1/600 of the span of the angle or 3/10 inch.
The angle rotation should be limited to 1/16 inch. When this approach is taken, there should be a minimum 1/4-inch separation between the bottom of the angle and the roof construction for the single story attachment. The horizontal component friction force between the shelf angle and the brick veneer must be checked to make sure that the brick will not slide down the slope of the roof of the single-story attachment. The maximum slope should be 14 degrees from horizontal, which is roughly a 3-inch rise for a 12-inch run. The BIA recommends that additional resistance to sliding can be achieved by welding 2-inch-long studs with at least 1/2-inch outside diameter to the bottom leg of the angle. These studs would project into the brick cores.