Repair and installation of asphalt shingle roofing

The Building Code sets the limit: on a standard slope, asphalt shingles can be installed starting at 1:3, or 4 inches of rise per foot. Between 1:6 and 1:3, it’s considered a low slope and the method changes: you need at least three layers of shingles instead of two. Below 1:6, no shingles are permitted, regardless of the manufacturer or the promised warranty. That’s the first thing our roofers check before recommending a replacement.

A shingle roof is an assembly. The eave protection extends at least 900 mm up from the edge and goes 300 mm past the inside face of the exterior wall: it’s what blocks water when an ice dam forms in February. Next comes the underlayment, then the starter strip at the edge, valley flashing over continuous decking, and wall and chimney flashing. When a roof leaks, the issue is more often one of these details than the shingle itself—and the water shows up first in the attic, on the insulation.

Each one-metre strip gets at least four nails, placed 25 to 40 mm from the side edges and never left exposed. Vertical overlap is at least 50 mm. At the ridge and hips, the pieces overlap by 150 mm and cover 100 mm on each side. The starter strips are held with a dab of mastic or a self-adhesive strip. These details—hidden once the job is done—explain why two roofs of the same age don’t age the same way.

A few shingles torn off by wind, a lifted flashing, a valley to redo: that’s repairable, and it’s best to do it quickly before water reaches the decking. Visible water infiltration in the attic also changes the equation: if the insulation is wet, you need to open it up. A full replacement is needed when granules are gone over large sections, when shingles curl or crack everywhere at once, when the decking feels spongy, or when the same roof has already been patched three times. An experienced roofer will tell you which applies—and why.

Our company repairs, maintains, and installs shingle roofs on homes on the Island of Montreal, in Laval, and on the North Shore—from bungalows to triplexes—and on small commercial buildings with mixed roofs. Annual maintenance extends the life of a shingle roof: it’s the best value before considering a full redo. RBQ licence 5856-8684-01, work covered by commercial insurance, crews available at night and on weekends when it’s leaking. To get pricing for your work, fill out the form: you’ll get a response in under 24 hours, free of charge.