When should a Flat Roof be installed instead of a shingle roof on a residential home

This week we are in Central London Ontario, where a client has asked Legacy Flat Roofing to install a new flat roof on a section of their home.

The client called us in as they were having issues with a section of their roof that had shingles installed.

When we inspected the home we recommended the client install a flat roof on the one section of their home, as the slope of the roof wasn’t enough to have water shed off the roof properly. What would happen during rainy weather, and especially ice and snow build up, combined with melting and freezing, the water was getting up under the shingles, and getting into the roof causing leaks and overall roof damage.

The video jumps in after we have already cleaned things off, but you can see from the condition of the wood deck that there were definitely issues. There was rotted wood, and many sections of the roof needed replacing before we could begin our project, so the prep work needed a bit more work than before.

When tearing out the wood deck its important to inspect the area for damp insulation and have that removed and then replaced, and to check that the roof trusses aren’t rotted or damaged. This roof was in good shape so we only needed to put down new plywood.

With a 2ply flat roof system, we use a peel and stick base sheet as the first layer that goes down onto the wood deck. With a peel and stick system, water cannot get back under the roof system, which is perfect for this application.

This should be a straightforward project, there was a shingle tie in at the ridge cap of the roof. Our plan is to leave the shingles in place just over the ridge cap where the slope is better, put the flat roof membrane up and over the ridge cap, and tie it into the shingles, and install a mastic polyurethane coating to provide an even better seal, so the roof is now fully protected and the water is controlled off the roof properly.

We installed new static square vents that matched the colour of the existing shingles and new flat roof, and we installed a new washroom vent boot to ensure maximum protection from water leaks.

Once that was completed and the membrane was primed we installed the peel and stick cap sheet. We install it in what we call a ‘shingle fashion’, meaning we start at the lowest point of the roof and work our way up, overlapping the layers as roofers do when installing shingles, as water always runs down (free tip of the day!). Then the overlapped seams are heat welded to create a water tight seam.

We’re really pleased by the way this flat roof system came out!