Mechanical · M-53D8P

Roof Curb and Flashing Detail

Materials

Elements

Facades / Cladding Roofs Decks Waterproofing / Flashing Insulation Drainage Site / Paving Connections / Plates Reinforcing Roof / Floor Openings

Connections

Welded Connection Bolted Connection Rebar Splice / Development Deck Attachment

About this detail

An eighteen-inch roof curb provided by the rooftop unit manufacturer bears on a curb angle-iron support, with the curb frame secured by thru-bolts or tack welds to the angle. The curb features a treated wood nailer, rigid field insulation, and a double-thickness gasket along the full perimeter between the unit and the top of the curb. A rooftop unit base rail is fastened to the curb using eighteen-gauge heavy-duty drill point fasteners spaced at twelve inches on center on each side with counterflashing. A twenty-gauge galvanized sheet metal pan is installed inside the curb to blank-off all areas except the duct openings, featuring an eighteen-by-eighteen access panel secured with sheet metal screws on three-inch centers and sealed with mastic duct sealant. The void areas within the curb are packed with fiberglass insulation, and all conduit and piping penetrations of the sheet metal panel are caulked and sealed, with a minimum six-inch deep condensate trap provided below.

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