NASCLA Accredited Commercial General ContractorThermal and Moisture ProtectionHard
A contractor is installing sheet metal flashing at a roof-to-wall intersection on a commercial building. The flashing needs to be integrated with the roof membrane and extend up the wall to prevent water intrusion. Which type of flashing detail is specifically designed for this application, typically involving multiple pieces to manage water runoff?
- ACounterflashing
- BReglet Flashing
- CStep Flashing
- DDrip Edge Flashing
Show answer & explanationAnswer & explanation
Correct answer: A. Counterflashing
At a roof-to-wall intersection, the base flashing (part of the roof membrane or a separate piece) extends up the wall. Counterflashing, often a separate metal piece, is then installed into the wall above the base flashing and extends down over it, creating a 'shingle' effect that prevents water from getting behind the base flashing.
Why the other options are wrong
- B. Reglet flashing refers to a groove cut into a wall into which flashing is inserted, but it's a component of the counterflashing system, not the complete detail for 'multiple pieces'.
- C. Step flashing is used on sloped roofs where the roof meets a vertical wall, with individual L-shaped pieces woven into shingle courses, not typically for flat or low-slope commercial roof-to-wall intersections.
- D. Drip edge flashing is installed at the eaves and rakes of a roof to direct water away from the fascia and prevent it from running back under the roof edge.
Counterflashing
A secondary layer of flashing, typically metal, installed above and overlapping the primary base flashing at a roof-to-wall or roof penetration junction, to protect the top edge of the base flashing from water intrusion.
- Protects base flashing at vertical surfaces
- Often installed into a reglet or surface-mounted
- Creates a 'shingle' effect with base flashing
- Crucial for watertight roof-to-wall transitions
Memory trick: Counterflashing 'Covers' the 'Critical' joint where roof meets wall.