EPDM (Ethylene Propylene Diene Monomer) is more than alphabet soup—it’s a synthetic rubber that has been available since 1962 for wide-ranging use against water intrusion. Being durable, flexible, non-slip, UV resistant, and waterproof makes EPDM a superior covering for residential flat roofs.
Before we get into the ABCs of EPDM, let’s talk about roof slope, which defines a roof as flat and determines the most functional systems and materials for a roof’s main job—-shedding water.
Slope: Rise over Run
The slope (pitch, angle) is the number of inches the roof rises vertically (the rise) for every 12 inches it extends horizontally (the run). For example, if a roof’s rise is 2” per 12” of run, the slope is expressed as 2:12, 2/12 or 2-in-12. Slope between 2/12 and 4/12 is low, between 4/12 and 21/12 is standard, and 21/12 or above is steep. Slope can be measured on the roof or in the attic, using an 18”-24” level and a tape measure. (Helpful videos on YouTube show the exact measuring process.)
A flat roof usually isn’t completely flat, but may have a minimum slope of ¼/12, an angle that’s still insufficient to shed water. A flat roof can’t be covered with asphalt or other types of shingles, because they need a minimum slope of 2/12-4/12 (and a double layer of underlayment). Metal isn’t suitable because it will rust wherever water doesn’t drain properly. Without slope to shed water, a flat roof requires a covering that is itself highly waterproof, such as TPO (Thermoplastic Polyolefin), modified bitumen, hot-tar-and-gravel built-up roof, PVC (Polyvinyl Chloride), or EPDM.
For residential flat roofing, EPDM rubber is a superior choice. It’s lightweight and resilient, resistant to temperature extremes, typically seamless, sustainable and environmentally friendly, and it offers a straightforward installation process.
From Failing to Fabulous
Now that we’ve covered slope and flat roof types, we’ll talk about a project that illustrates the actual process and results.
TSW Roofing Solutions recently installed Firestone’s RubberGard™ EPDM roof system on a deteriorated flat roof that is also a second-story porch. First, the tearoff: we removed the railings, posts, and previous roofing and underlayment, then checked the roof deck for rotted wood.
After cleaning the deck we installed 1” thick Firestone Polyiso insulating deck panels with plates and screws. We then installed a Firestone Black 0.060” fully adhered (glued) membrane. All installation was done according to manufacturer’s specifications.
For this project, we also fabricated and installed new 16 ounce copper counter flashing to the walls, a copper sill plate for the walk-out door, and copper built-in gutters for the perimeter of the roof areas. We installed Firestone’s QuickSeam accessory flashings to the seams, gutters, and penetrations.
Finally, we re-installed the posts and railings, caulked all of the screw holes, and applied two coats of exterior paint to the railings.
The result is an attractive, durable, watertight, low maintenance flat roof that protects the home and offers worry-free value to the home owner.
This blog post is brought to you by TSW Roofing Solutions, Inc.
We’re here to solve your roofing problems!
PS—-You can learn more about EPDM flat roofing at these websites.