Guides
Flat Roof Guides
Plain-language explanations to help you understand your roof and make good decisions.
Flat Roof Leaks: Where They Start and What to Do First
Most flat roof leaks start at details — seams, flashings, penetrations and drains — rather than in the open field of the membrane. Water often travels before it shows inside, so the drip location is a clue, not the answer. Safe first steps are all inside the building.
Ponding Water on a Flat Roof: Drainage, Slope and When to Worry
Flat roofs are not truly flat — they are designed with a slight slope toward drains, scuppers or gutters. Ponding happens when water can't follow that path because of blocked drains, sagging structure, compressed insulation or a roof built with too little slope. Persistent ponding shortens membrane life and adds load.
Repair or Replace a Flat Roof? A Practical Way to Decide
Repair makes sense when problems are isolated and the rest of the roof is sound. Replacement makes sense when failures are widespread, insulation is wet across large areas, drainage needs redesign, or repeated repairs are adding up. The decision is about the whole roof, not one leak.
How Long Does a Flat Roof Last?
There's no single number. Many well-installed, well-maintained flat roofs give roughly 15 to 30 years of service, but that range depends heavily on the membrane, the quality of installation and detailing, how well the roof drains, the climate and how it's maintained. Some roofs fail much sooner; some last longer. The roof's actual condition matters more than its age.
Why Do They Put Gravel on Flat Roofs?
Gravel on a flat roof does one of two jobs. On a built-up (tar-and-gravel) roof, it's embedded in the top layer of asphalt to protect it from sunlight, weather and foot traffic. On a ballasted single-ply roof, larger loose stone holds a membrane and insulation in place by weight. They look similar but work differently, so they're assessed and repaired differently — and gravel shouldn't be moved without understanding which you have.
How Long Does It Take to Replace a Flat Roof?
A small residential flat roof, such as a garage or rear addition, is often replaced in one to a few working days once work starts. Larger homes and commercial roofs can take from several days to several weeks. The actual duration depends on size, how many layers come off, deck repairs, insulation, the number of details, access and especially weather. Planning, scoping and scheduling add time before work begins.
Flat Roofs in Ottawa Winter
Flat roofs are common in snowy climates and work well when they're designed and drained properly. The real winter risks are blocked drains, ice damming at edges, freeze-thaw damage to small defects, and unusual snow drifts. Shovelling a roof yourself is dangerous and usually unnecessary; if you're concerned, have the roof assessed from a safe position by a professional.
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