There are a wide variety of options for do-it-yourself flat roof installation. The alternatives include modified bitumen, built-up roofing, Ethylene Propylene Diene Monomer (EPDM) and seamed metal roofing. Currently, EPDM is the most used flat roofing method because of the ease of installation, which requires the material to be glued in place. EPDM is a rubber-like sheet of membrane.
Visit the local building department to ascertain what the rules are for flat roof installations. Many building codes will not permit reroofing over more than two layers of roofing materials
The surface of the roof must be clean, dry and in solid structural condition. Remove jagged or jutting items and secure all loose decking. Weak sheathing or roof framing members must be replaced. Do not install EPDM over petroleum-based roofing materials, such as shingles, asphalt, tar, felt paper or rolled roofing, because the oil in the materials will cause the EPDM to blister and leak.
If you cannot clean the deck, or the surface has petroleum-based material, install 5/8-inch plywood or polyisocyanurate board (with fibreglass backing) to the existing deck. The polyisocyanurate board will provide a smooth surface for installing the EPDM and also provide insulation.
Install metal drip edge along the edge of the roof. Metal flashing should also be applied where the roof connects to an adjoining wall.
Do not attempt to install EPDM in temperatures below 10 degrees Celsius when using a latex-based adhesive. The temperature will have to remain 10 degrees C or higher at least for a minimum of 48 hours after the adhesive is applied for the glue to cure properly. Usually, the latex must be stored in temperatures of 50 to 70 prior to application. Neoprene bonding adhesive must be applied in temperature of 4.44 degrees Celsius, which must be maintained for at least 24 hours.
Allow the membrane to extend about 3 inches over the edge of the roof and 12 inches up the sidewalls. Open up the membrane before you're ready to begin the actual installation. The membrane must be flattened out before being placed in final position. It may take approximately 30 minutes for the membrane to acclimate to successfully get rid of any creases or wrinkles.
Use the approved cleaner on the underside of the membrane before applying the adhesive. Do not apply the glue to the seams, which must be sealed separately. Use a paint roller and apply the adhesive evenly over the sheet and on the deck. Let the adhesive dry to a sticky consistency before putting the membrane in place. Use a push broom to facilitate the bonding of the membrane to the deck.
Overlap the seams at least 3 inches. Usually, a seam cleaner must be applied to both sheets of membranes. Use the appropriate tape for sealing the seams.