Parapet Wall Flashing Termination Without Counterflashing
During a roof replacement on a 30-year-old concrete-frame building, the crew is installing SBS-modified bitumen wall flashing at a concrete parapet. The new roof membrane termination is 8 in. above the roof surface. The parapet is 30 in. high, with an uneven stucco finish. The crew cuts a 3/4 in. deep horizontal reglet at 8 in. above the roof, inserts the top edge of the flashing, seals it with polyurethane sealant, and fastens the flashing through the membrane with 1 in. roofing nails at 12 in. on center. No termination bar or counterflashing has been installed. The roof slope is 1/4 in. per foot toward interior drains, and the parapet wall has visible hairline cracks. The owner’s representative asks whether this termination meets typical NRCA and code requirements and whether the sealant alone is acceptable.
1. Evaluate the termination detail as described.
Read the worked answer
The termination is not acceptable as a completed wall flashing detail. The 8 in. height may meet a common minimum above the roof surface, but height alone does not make the termination watertight. Problems include:
- Sealant-only reglet termination: sealant is a maintenance item, not a structural termination. A 3/4 in. reglet with sealant and no termination bar or counterflashing relies on adhesion and is vulnerable to movement, UV, and water standing at the reglet.
- Fasteners through the membrane: nails at 12 in. on center penetrate the flashing and create holes. Unless detailed and sealed as part of an approved termination, these are leak paths.
- No counterflashing: the top edge is exposed. Counterflashing sheds water over the flashing and protects the reglet.
- Uneven stucco and hairline cracks: the substrate may not provide a continuous sealant bond, and cracks can admit water behind the flashing.
The detail should be corrected before the roof is accepted.
2. What corrective detailing should be required?
Read the worked answer
Require a proper two-piece termination. Install a termination bar over the top edge of the flashing, fastened at the manufacturer’s spacing and sealed with an approved sealant. Install counterflashing into the reglet or over the termination bar so water sheds over the flashing; seal the counterflashing top edge, not the weep path. Remove the nails that penetrate the membrane and replace them with an approved termination method; any abandoned holes must be repaired per the manufacturer. Prepare the stucco-remove loose material, address cracks, and use a compatible sealant or substrate repair. Confirm the flashing height is at least the code/manufacturer minimum above the roof and above the highest expected water level. The wall flashing should be stripped in over the roof membrane with a minimum lap and sealed. If the existing reglet is too shallow or deteriorated, install a surface-mounted termination bar and counterflashing rather than relying on the reglet.
3. What inspection or water testing would you require before closeout?
Read the worked answer
Inspect the full wall flashing for lap width, stripping, termination bar fastening, counterflashing engagement, sealant continuity, and substrate condition. Perform a hose test at the wall termination, starting low and moving upward, while an observer checks inside for leakage. Because the wall has hairline cracks, also inspect the wall surface above the flashing and require repair of cracks that can admit water. Record photographs and a detail sketch. Do not accept the area on the basis of sealant alone; the test should confirm the two-piece termination and counterflashing perform as a system.