Flashing and Drainage Detailing
Domain 4: Flashing and drainage detailing
This domain tests whether you can follow water over and through a wall assembly. The exam focuses on continuity, lap direction, end dams, and the difference between a flashing and a sealant.
Core rules
- Laps are shingle-fashion: upper materials overlap lower materials so gravity carries water outward. Reverse laps trap water.
- The weather barrier is the wall's drainage plane. Flashing must integrate with it, not behind it. Head flashings shed water over the barrier below; sill pans collect and drain window sill water.
- Roof/wall intersections require step flashing woven with roof courses, counterflashing at the wall, and kick-out flashing at the low end to direct water away from the wall.
- Weep screeds at the base need weep openings and a sloped flange; casing beads at openings need a drainage path. Sealant alone is not a flashing.
- Penetrations such as pipes, vents, and deck ledges need flashed, sealed, and drained details; sealant is a secondary defense.
Worked example
A roof plane dies into a sidewall with no kick-out flashing; the stucco below is stained. Reasoning: step flashing sheds water down the roof, but at the eave the water can run off the roof edge and behind the wall cladding. A kick-out turns the last piece of flashing out onto the roof, away from the wall. Without it, the stain is consistent with chronic wetting. Report the missing kick-out and recommend correction.
Traps
Do not accept caulk at a head or sill as flashing. Do not assume flashing exists because a trim piece is present. Do not miss reverse-lapped housewrap or weather barrier behind lath. Do not overlook the bottom termination.