You may have an older urban home with an existing upper story door leading out to a newish, flat EPDM rubber roof. The space looks perfect as a spot for a patio table for morning coffee or a few pots for a small herb garden. You can safely cover the roof to protect the EPDM membrane, using a deck composed of duckboards to permit drainage and cleaning.
Things You'll Need
- Measuring tape
- 2-by-2 lumber
- 1-by-4 deck boards
- Galvanized deck screws
- Drill with screwdriver bit
- Aluminum flashing
- Construction adhesive
- Caulk gun
- Carpenter's pencil
- Spirit level
- Circular saw
Measure the space where you'd like to have a deck on the EPDM roof. Aim for a length and width that can easily be broken into square modules of 6-by-6 feet or smaller. For example, you can create a deck measuring 12 feet square using four 6-foot-square duckboards.
Support each duckboard with 2-by-2 sleepers, either redwood, cedar or pressure treated. Lay out the sleepers on your workspace, with one sleeper beneath each end of the duckboard and intermediate sleepers every 16 to 24 inches between the ends. A 6-foot-square duckboard, for example, can have five 6-foot-long sleepers laid out in a parallel line like fence pickets. Try to work off of the roof, as an accidentally dropped sleeper edge, saw blade or deck screw can pierce an EPDM roof.
Screw 1-by-4 deck boards -- either pressure treated or composite -- to the sleepers with two galvanized deck screws at each junction where the deck board meets a sleeper. Space each deck board 1/4 inch apart. A completed 6-foot-square duckboard, for example, will contain a series of 6-foot-long deck boards and resemble the slatted, slightly raised floor of a wooden sauna.
Flip the duckboard over. Glue a strip of aluminum flashing to the bottom of each sleeper with a squiggly application of construction adhesive from a caulk gun. Flip the duckboard right side up again and lay it down on a work surface. Let the adhesive cure according to manufacturer’s instructions, typically for at least 24 hours. The flashing keeps the sleeper from sticking to the roof, especially on hot days.
Lay the duckboards carefully in place on the EPDM roof. Place one just under the access door to the roof so residents and guests avoid stepping on the EPDM surface.
Tips & Warnings
- Taper the sleepers before assembly if you prefer to create level duckboards and your EPDM roof is not perfectly horizontal. Scribe the lower edge of a spirit level on the duckboard with a carpenter’s pencil. Cut the mark on the sleeper with a circular saw.
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