Can I add a partial second storey over just the back of my Ottawa home?

Yes, a partial second storey over the back of the house is a common way to add space. It keeps the front of the home largely unchanged, which can help with neighbourhood fit and with zoning, and because the footprint is smaller it can cost less than a full second storey. Whether it works for your house depends on the structure below and your zoning.

A rear partial storey is often used for a primary bedroom with an ensuite, or for a couple of bedrooms and a bathroom. Cost depends on size, structure, mechanical work and finishes, so treat any figure as perspective and ask for itemized quotes.

Structurally, you're loading only part of the existing foundation and walls, so reinforcement may be less extensive than for a full storey, but that isn't guaranteed. The junction where the new storey meets the existing lower roof is more complex, and the engineer has to design load transfer there and allow for snow drifting against the taller wall. Ask for a written engineering fee quote.

On zoning, setting the taller part back from the street can reduce its impact on neighbours. Your zoning sets maximum height, lot coverage and setbacks, so check your property's zone; Ottawa currently has two zoning by-laws in effect, 2008-250 and the new 2026-50, while appeals are resolved. If a rule can't be met, a minor variance from the Committee of Adjustment is the route, and the 2026 urban fee is $3,759 in total.

The stepped roofline where the new higher roof meets the original lower one needs careful flashing and detailing to keep water out. Ice damming at that transition is a real risk in freeze-thaw weather, so ask your contractor how they'll protect and ventilate it.

The foundation under the new storey matters. If it sits over a full basement, the existing foundation may be adequate once an engineer checks it. Over a slab or crawlspace, it may need strengthening. Under the Code, footings on clay or undefined soils must be at least 1.2 m deep and not less than the depth of frost penetration, and on sensitive clay, including Leda clay, footing sizes must be engineered.

The new part must meet current energy rules; the Code's addition table calls for R-60 in an attic ceiling and R-19 plus R-5 continuous insulation in above-grade walls, unless your designer uses a compliance package. Electrical work needs an ESA notification or permit, and gas work is done by a TSSA-certified gas technician. A building permit is required; fees for additions are $12.75 per $1,000 of construction value, minimum $117. To compare contractors, browse the Ottawa Construction Network directory.

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

• 613Bins
• RenoMotion Inc.
• MAK Construction and Development Inc
• M.O.T. CONSTRUCTION INC.
• Custom By Arie