Contact the experts at Avenue Road Roofing when you need repair or replacement of a flat roof on a home or commercial building.

Tar and gravel roofs need attention when the gravel begins to separate from the asphalt. You can tell this is happening when you see a sandy-like residue on the surface that appears muddy or dirt like when scraped under foot.

Other indicators of trouble include blisters in the surface, evidence of tears or fissures in the membrane, algae or moss growth, active leaks or internal stains, appearance of exposed felt layers.

Modified bitumen flat roofs need repair when you see debonded seams at laps of the material or at perimeter edges. Blisters or wrinkles indicate incorrect application by not fully bonding the membrane. “Alligatoring” (roof looks like the skin of an alligator) or blisters indicate overheating of the membrane.

No short cuts should be taken when it is time to install a new flat roof. Old materials should be removed down to the bare substrate (roof deck) to allow full examination, removal of water soaked insulation (helps increase the load carrying capacity of the roof) and repair of wood damaged by water (a possible health hazard because rotting wood can produce mould) or carpenter ants.

If you have a tar and gravel roof and are considering adding a new layer, make sure you find out first how many layers are already in place. Each layer weighs about 750 lbs. per 100 square feet. In downtown areas or older city neighbourhoods, it is not uncommon to find five layers on a roof – or about two tons of material per 10’x10’ area – and the roof may not be able to take on the weight of another layer. Sooner or later, the old roofing has to be removed, usually by hand because access issues or the size of the roof preclude the use of machinery.

Special attention should be applied to doors leading onto flats which have less than six inches of clearance between the roof’s surface and the sill of the door, where snow or rain can accumulate. Doors having this minimal clearance should be removed and re-installed or replaced to allow for proper waterproofing practices.

You should also know that flat roof mounted skylights are often a leak source because wind-blown snow can be forced into frames that don’t have proper membrane and metal flashing detail. It’s also important to inspect for moisture between the panes of the acrylic domes or glass on skylight units.

One last thing: ponding of water on flats can be an issue because of the risk of West Nile Virus. This can be addressed by using tapered insulation systems or by re-structuring the roof substrate to achieve proper drainage. Adding roof drains is also an option in some flat roof configurations.