This summer our crew roofed a new custom home going up on a heavily treed lot in Stouffville. The house is modern and flat-roofed, with several roof sections at different heights, and the builder needed it closed in before the interior trades could start. We installed a 2-ply modified bitumen flat roof across every section.
Why a 2-ply system on this house
A flat roof doesn’t shed water the way a pitched roof does. Snow sits on it, meltwater sits on it, and every seam has to hold. A 2-ply modified bitumen system puts two layers of membrane between the weather and the house: a base sheet first, then a granulated cap sheet on top with its seams offset from the ones below. If one layer is ever nicked, the second is still there.
On a modern custom home with parapets, walls rising off the roof and several separate roof areas, that redundancy matters most at the edges and joints. Those are the spots we spend the most time on.
Working on a site that’s still a construction site
The roof went on while the house was still framed and open, so we worked alongside the builder’s schedule rather than on a finished home. Every roof edge had temporary guardrails, material was lifted to each level as we needed it, and each section was sealed before we moved to the next so the framing below stayed dry.
The different roof heights meant a lot of wall transitions. Where the lower roofs meet the walls of the upper storey, the membrane runs up the wall and gets properly flashed, because that’s where flat roofs on houses like this usually leak first.
Flat roofs on modern homes around York Region
More new builds in Stouffville, King, Aurora and Richmond Hill are going with flat and low-slope roofs. They look clean, but they need a real flat-roof system, not shingles pushed onto a low pitch. If you’re building or renovating, see our flat roofing page, or our local pages for Richmond Hill, Aurora and Newmarket.
Questions about 2-ply flat roofs
What is a 2-ply flat roof?
It’s a flat roof made of two layers of modified bitumen membrane: a base sheet and a cap sheet. The seams of the two layers are offset so there’s no straight path for water to get through.
Is a 2-ply roof better than a single-ply roof?
For most homes in Ontario, a 2-ply modified bitumen roof gives more protection at seams and edges than a single layer, which is why we recommend it for new flat-roofed houses and additions.
Can you install a flat roof while the house is still under construction?
Yes. We work with builders to roof new homes as soon as the deck and parapets are ready, so the house can be closed in and the interior work can start.
Do you do flat roofs on existing homes too?
Yes, including rear additions, garages and older flat roofs that need replacing across Toronto and York Region.
Building or renovating with a flat roof?
Call the Spiros family team at 416-286-7759 or send us your plans and we’ll quote the roof in writing.
Reviewed by the Spiros Aluminum & Roofing family team, roofing in the GTA since 1986.