Skylight frames should overlap the curb a minimum of how many inches to act as a counterflashing or require a separate counterflashing?

Skylight frames should overlap the curb a minimum of how many inches to act as a counterflashing or require a separate counterflashing?

• A. 1 inch
• B. 2 inches
• C. 3 inches
• D. 4 inches

Answer: (C)

A proper flashing detail at a skylight hinges on having enough overlap so the skylight frame itself can function as counterflashing. When the frame overlaps the curb by three inches, that overlap provides a sufficient surface for sealing and directing water outward, preventing it from seeping under the joint between the curb and the roof. This three-inch minimum ensures the flashing is tied in cleanly with the roof membrane and can be sealed effectively around fasteners and joints. If the overlap is smaller than three inches, water can track behind the frame, which is why a separate counterflashing is required to intercept the water and cover the seam it would otherwise exploit.

A proper flashing detail at a skylight hinges on having enough overlap so the skylight frame itself can function as counterflashing. When the frame overlaps the curb by three inches, that overlap provides a sufficient surface for sealing and directing water outward, preventing it from seeping under the joint between the curb and the roof. This three-inch minimum ensures the flashing is tied in cleanly with the roof membrane and can be sealed effectively around fasteners and joints. If the overlap is smaller than three inches, water can track behind the frame, which is why a separate counterflashing is required to intercept the water and cover the seam it would otherwise exploit.