Is a pop-top second storey feasible for a war-era bungalow in Ottawa?

Pop-tops are a common way to expand post-war bungalows, which often sit on good-sized lots. Whether one is feasible for your house depends on its structure, foundation and soil, and older houses bring specific questions that need careful engineering.

A pop-top means removing the existing roof and building a full second storey on top of the existing main-floor walls. It can roughly double the living space without a bigger footprint. The cost depends on size, structure, systems and finishes, so treat any figure as perspective and ask for itemized quotes. Whether it beats moving depends on prices on your own street, which a local agent can help you compare.

The foundation comes first. War-era foundations were built for one storey and may be poured concrete or block, with or without reinforcement. A structural engineer has to confirm whether they can carry a second storey. Many foundations that have been kept dry are in reasonable shape, but decades of movement on clay soils can cause settling and cracking. On sensitive clay, including Leda clay, the Code requires footing sizes to be engineered. If reinforcement is needed, options include underpinning or other strengthening the engineer specifies.

Footing depth is worth checking. 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. A full basement usually goes well down, but a shallow crawlspace at the back may not. Test holes before committing to a design can avoid surprises mid-construction.

Wall framing in these houses is often 2x4, which raises two questions: whether studs and headers need reinforcement for the new loads, and how to improve insulation. Some projects add exterior insulation to the main-floor walls during re-siding. Renovations fall under Part 11 of the Code, which requires performance after an alteration to be at least equal to what it was before; your designer will explain what that means for your walls.

Electrical often needs updating. A second storey adds load, and an older panel may not have room; an electrician's load calculation tells you whether a service upgrade is needed. Electrical work needs an ESA notification or permit. Any old wiring types should be assessed by the electrician before insulating.

Plumbing in older homes may include old drain stacks and supply lines, and a pop-top is a convenient time to replace them while running lines to the new bathroom.

Renovators aren't licensed by the HCRA the way new home builders are, so get contract and warranty terms in writing. You can browse addition contractors in the Ottawa Construction Network directory and compare itemized quotes.

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

• Luxe Painting and Renovations
• RenoMotion Inc.
• Dreamwood Construction & Renovations
• The Granite shop
• The Deck Store Inc