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Where to Flash

The building codes and Brick Industry Association ( standards call for through-wall flashings at several critical points: where a roof abuts a brick wall, within one course of brick above and below doors and windows, and just above grade below ground-floor level.

Rake sidewalls. Wherever a gable roof — on a garage, for example — meets a higher brick wall, you’d better pay attention. On a lot of the new houses I inspect, the sidewall brick lands right on the roof sheathing, with maybe a doubled rafter underneath. Worse, I actually see houses where the brick comes right down on top of the step flashing — those will be fun jobs to reroof.

Without getting into the issue of structural support, I want to point out that unless there's a through-wall flashing abov the garage roof surface, any water that gets behind the brick will be headed right down into the framing and the interior finishes.

Unfortunately, the kerf method appears to have totally replaced use of proper through-wall flashings at roof-to-wall intersections. Amittedly, doing the job correctly is a detailed process that requires coordination between the roofer and the mason (see slideshows). But it’s the only way to guarantee that water entering the brick from above will not cascade down into the living space below.

Window and door heads. There should be through-wall flashings below the first course of brick along the top of windows and doors. The steel angle is for structural support only; it should not be used for flashing. For example, some contractors will lap the felt or housewrap over the top leg and rely on the angle to keep water out. More often, though, there’s no flashing anyway, and the steel is installed on top of the housewrap.

Window sills. Through-wall flashing should also be placed under the sloped course of brick (typically rowlock) immediately below the window. This is meant to catch any water that makes it into the wall cavity through or around the window. Sills should always be sloped at least 15 degrees, per BIA standards.

Above grade. Too often, the bottom courses of brick are simply buried in the soil. There should be a through-wall flashing under the last course of brick above grade; this course must also be below the bottom of the first-floor framing. Flashing at this location serves two purposes: It prevents ground moisture from wicking up into the wall, and it catches any water coming from the cavity above and sends it outside.