Architectural · A-XN3TR

Roof Drain and Overflow Drain Assembly on Wood Deck

Materials

Elements

Roofs Waterproofing / Flashing Insulation Drainage

About this detail

The roof assembly features a primary roof drain and an adjacent roof overflow drain with an overflow standpipe or collar, both equipped with membrane clamping rings. The secondary overflow drain sits two inches minimum above the primary drain level. The roof membrane laps into the compression ring per manufacturer instructions, maintaining no seams within six inches of the ring. A primed four-pound lead flashing sheet adheres to the base layer at the drains and drain flanges. Pressure-treated wood blocking matches the insulation thickness around the drains, and underdeck clamp rings secure the assembly from below. Four-inch minimum insulation forms the roof sump, supplemented by a minimum R-10 spray foam insulation applied around the drain bodies.

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