Wall and through-wall flashings, counterflashings, reglets, copings and parapet terminations
Through-wall flashings intercept water inside a wall and lead it out through weep openings. The exam tests continuity, end dams, laps, reglets and counterflashing coordination.
Core rules
- Install a continuous flashing at the base of the wall cavity, turned up at ends to form end dams. End dams are mandatory where the flashing terminates at a wall, opening or joint.
- Lap joints in the direction of flow; use soldered, welded or adhesive laps as specified. Do not rely on a bead of sealant as the primary lap.
- Provide weep holes or vents above the flashing so water can escape. Keep weep openings clear and place them at the low point.
- Counterflashing must overlap the base flashing and terminate in a reglet or surface-mounted receiver. A common minimum overlap is 4 in.; verify manufacturer and code.
- Coordinate flashing with air/vapor barriers, insulation and cladding attachments. Penetrations through the flashing need their own seals and end dams.
Worked example
A 30-ft masonry veneer wall gets through-wall flashing that stops 2 in. short of each end and has no end dams. Weeps are drilled at 4 ft on center. During a wind-driven rain test, water runs along the flashing and exits at the wall ends, staining the soffit. The fix is to extend the flashing into the returns, turn up 2-in. end dams, lap joints shingle-fashion, and space weeps at the manufacturer's or code spacing, which is often closer than 4 ft. Sealant alone would not correct the missing end dams.
Traps
Skipping end dams; reverse-lapping; sealing weeps; using a surface counterflashing with too little overlap; forgetting that through-wall flashing must be continuous behind cladding; mismatching membrane and metal.