This week as summer wraps up were out in the central area of London Ontario, working on a flat roof that’s part of a beautiful century home, at the rear of the residence.
We were called out as their existing flat roof was showing its age. It was an existing 2 ply modified bitumen flat roof, we were able to fully inspect it and see that it was in good enough condition for us to roof over it. The great part about 2ply systems is that they are easy to roof over, if the existing surface is in good condition. That wasn’t the case for this project.
Our first step was to clean the entire existing flat roof section off, removing all the old loose pieces of roof, any debris, and get it clean and dry. Because the existing 2ply surface was warped and crooked, we didn’t want to install the new system right on top of that, so the next step is to install a substrate.
For those of you that don’t know, a substrate is the later of material that serves as the foundation for the roofing system. It is the surface on which the roofing material is installed, and it provides support and stability for the flat roof. The substrate is made of boards that we screw onto the existing roof before installing the next part of the flat roof system.
Once the substrate is down we roll on a primer, which is a red liquid adhesive that is applied to the roof before we install the waterproof base sheet/membrane. Once the membrane is installed, we install aluminum metal drip edge flashing around the permitter of the flat roof section. The purpose of the metal flashing is to shed water correctly, and it’s a very nice, clean and neat way to cover up the transition between the flat roof and the walls of the home.
Then for the final step we put down more primer adhesive, and then install the cap sheet. Once we have laid them out side by side with a little overlap, we circle back and close up each seam by heat welding them together. This activates the asphalt on the back of the cap sheet, creating a perfect seal on the roof, and providing another waterproof layer.
We’re proud of this project – we were able to take an old flat roof that was past its life cycle and give the owner at least 20 years of peace of mind with this new flat roof system.