What roofline options work best for a partial second-storey addition in Ottawa?

The roofline for a partial second-storey addition is both an architectural and a structural decision. It affects curb appeal, ceiling heights upstairs and how the roof performs through Ottawa winters. Whatever shape you choose, your designer or engineer will design it for the snow, drift and wind loads the Building Code requires for your location.

The gable roof is a common, cost-effective choice. Its simple peaked profile sheds snow well, and on a bungalow a gable that runs perpendicular to the existing roof can create a clean transition between old and new. Gables also leave some attic space for insulation and ventilation.

A shed roof, sloping in one direction, gives a more modern look and suits additions over the back of the house where street appearance matters less. It is structurally simple. Low slopes can be more prone to snow build-up and ice damming, so ask your designer what pitch they recommend and why.

A hip roof slopes on all four sides. It tends to handle wind well and can suit houses with a traditional character, but it is usually more complex to frame and leaves less attic space than a gable. Ask your contractor to price the options so you can compare.

The transition where the new second storey meets the single-storey section is the most leak-prone part of a partial addition. Valleys and roof-to-wall junctions need careful flashing and a self-adhering waterproof membrane, and the big temperature swings Ottawa sees put stress on those joints every year. Ask your contractor how far they run the membrane at valleys and transitions and how they will flash the wall where the lower roof meets the new upper storey.

For materials, try to match or complement the existing roof. Architectural asphalt shingles are a common choice; standing-seam metal is another option that sheds snow readily and tends to last longer but costs more. Ask for the wind rating and warranty terms of whatever product is proposed, and get them in writing.

Good insulation and ventilation matter whichever shape you pick. For an addition, the verified Zone 1 value for a ceiling with an attic is R-60, and proper ventilation helps reduce ice damming.

A second-storey addition needs a building permit from the City of Ottawa, and the roof structure will be shown on your drawings. Ask contractors to itemize framing, roofing and flashing so you can compare quotes. You can browse addition contractors in the Ottawa Construction Network directory at justynrookcontracting.com and compare quotes.

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