What roofing material works best for an addition in Ottawa's freeze-thaw climate?

Ottawa winters bring frequent freeze-thaw cycles, with temperatures crossing zero again and again. Water that gets into or under roofing freezes, expands and thaws, and over time that is one of the main causes of early roof failure. Choosing a roofing material and details suited to that climate from the start saves repairs later.

Architectural asphalt shingles are a common, practical choice for additions. Laminated shingles are heavier and more durable than older three-tab shingles, they're widely available, and they're often the easiest way to match the existing roof. Ask for shingles with good wind resistance and an algae-resistant coating, which helps prevent the dark streaks that show up on many roofs. Get the warranty terms in writing, including what's covered for labour versus material.

Standing seam metal roofing is a premium option that suits snowy climates well. Metal sheds snow readily, which helps reduce ice buildup at the eaves, needs little maintenance and lasts a long time. Panels are fastened with clips that let them expand and contract. It costs considerably more to install than shingles, though its long life can narrow the gap over time. Plan for snow sliding off: keep doors, walkways and lower roofs out of the path, or add snow guards.

Cedar shakes are beautiful but demanding. They need regular cleaning and treatment, and individual shakes split and curl over time with freeze-thaw. Wood roofing also raises fire questions, so ask your designer whether any treatment is needed for your situation. Unless your house already has cedar and matching matters, many people choose another material for an addition.

Synthetic slate and composite shingles imitate natural slate at a lower cost than the real thing and tend to flex rather than crack in the cold. They can be a good option when your addition needs to match an existing slate or high-end roof on an older home. Ask about the product's track record in cold climates.

Whatever the material, the details beneath it matter most. Self-adhered ice and water membrane at the eaves and in valleys protects against ice-dam leaks, and some roofers run it further up the roof or across low-slope sections. Ask how far your contractor plans to run it. Balanced attic ventilation, with intake at the soffits and exhaust at or near the ridge, plus good insulation and air sealing, keeps the roof deck cold so snow doesn't melt and refreeze at the eaves.

For an addition, also check how the new roofing will meet the old: matching colour and profile, flashing at the wall junction, and whether part of the existing roof needs replacing. Ask roofing contractors for itemized quotes that list the material, membrane, flashing and ventilation separately.

---

Looking for experienced contractors? The Ottawa Construction Network connects homeowners with qualified professionals:

• Justyn Rook Contracting
• JC Carpentry
• Denys Builds Designs Renovations
• Steven Labelle - Your Complete Home Renovator
• Rrenovatios