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Flat roofs create an easy staging area for off-the-shelf solar mounting arrays, but just as importantly, they make it much easier to perform future maintenance and repair.


White or light colored “cool” roofs are highly recommended for hot climates. They also earn points under some green building programs. Some EPDM comes pre-colored (preferred), or you can coat them after installation.


 


According to the International Building Code, the typical built-up flat roof that uses tar or asphalt goes by the guideline that for every foot of a flat roof, a minimum of ¼” must step up or down.


This is the basis for calculating the angle, which is approximately a 1.19° slope. This angle may need to change if you choose an alternative building material for the membrane of the roof. A common slope used that covers most materials is 2:12, which means that for every foot, the roof steps up or down 2”.


In anticipation of the roofing project, Ledman and his team built the pitch they desired into the actual framing of the house, creating the ¼” per foot drop required to shuttle rainwater off of the roof and into a downspout. Installation of the EPDM roof took two days, with scuppers installed to direct the rain where the owner wanted it to go.


“One of the beauties of EPDM is the ease with which it can be installed,” St. Hilaire says. “Basically, it’s a rubber that looks like tire tubes, and it has a similar flexibility.”


For Ledman’s multi-family dwelling, St. Hilaire first put down 3” of foam insulation—increasing the R-Value of the roof—and then used .060”-thick sheets of EPDM. The sheets come in an assortment of widths, including 10’ x 50’, 10’ x 100’, 16.5’ x 100’, 20’ x 100’ and 25’ x 100’.


Once the insulation is in place, St. Hilaire says, the contractor essentially has three choices for how to install the rubber on top of the insulation. His preferred method, and the one he employed on the Portland project, is to glue it down. His reasoning is simple: “You are not adding a significant amount of weight to the roof.”


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