Basement Renovations near you

Natural Resources Canada is blunt about it: don't insulate a basement from the inside if it has moisture problems such as leaks, dampness, efflorescence or blistering paint, or the new walls will rot. Fix the source first. That may mean regrading the soil so it slopes away from the house, extending downspouts, sealing cracks, repairing or adding foundation drainage or installing a sump pump, and it is worth waiting through a spring thaw and some heavy rain to confirm the basement stays dry.

Moisture also comes from the concrete itself. NRCan notes that concrete holds a lot of water and recommends allowing about a year of drying time before insulating or renovating a new basement, or the basement of a house that has been raised.

Basement walls stay cold for much of the year, and warm, humid indoor air that reaches them will condense. That is why the air and vapour barrier matters as much as the insulation. For framed walls, NRCan describes using polyethylene sheeting, a breathable polyamide vapour retarder film sometimes called a smart barrier, or the airtight drywall approach, where the drywall itself is carefully sealed. Whichever method is used, the barrier must be continuous across the wall and the header space at the top of the foundation.

Some materials don't belong in a basement. NRCan advises against asphalt building paper, or tar paper, inside the house because it can release toxic vapours, and warns that foil-faced insulation board may deteriorate in contact with cement and mortar. Ask your contractor how the floor will be insulated or separated from the slab, and choose flooring and baseboards that can tolerate some moisture now and then.

A bedroom in a basement needs a way out other than the stairs. Building codes require a bedroom to have an exterior door or a window that opens from the inside without tools and is large enough to climb through. In Ontario, for example, the City of Ottawa's building code advisory sets out that the open window must give an unobstructed area of at least 0.35 m², with no dimension less than 380 mm, and that a window opening into a window well needs a clearance of 550 mm in front of it so a person can get out. Other provinces base their rules on the National Building Code but may differ, so confirm the requirements with your municipality before cutting into the foundation.

Most municipalities require a building permit to finish a basement, especially when the work adds a bedroom or a bathroom, changes plumbing or wiring, or enlarges a window opening. Cutting or widening an opening in a foundation wall is structural work for a qualified contractor, sometimes with an engineer's design, and never a weekend project.

Whether a basement apartment is allowed depends on your municipality's zoning bylaw, and making it legal involves a permit, a fire separation between the units, smoke alarms, safe exits and a minimum ceiling height. Ontario's guide to second units, for instance, calls for a 30-minute fire separation between units and a ceiling height of at least 1.95 m in a basement unit. In Quebec, many municipalities allow an intergenerational or accessory unit under their own bylaws, so start with your city's urban planning department before drawing anything.

Radon is a colourless, odourless radioactive gas that seeps from the ground into homes, and the basement is usually where levels are highest. Finishing it turns the part of the house with the most radon into a place where people spend hours every day. The Canadian guideline is 200 becquerels per cubic metre (Bq/m³), and Health Canada recommends taking action when a long-term test shows a higher level: the higher the result, the sooner.

Health Canada's measurement guide calls for a test with at least 91 days during the heating season, with the detector on the lowest lived-in level, in a spot where someone spends more than four hours a day. Testing before you finish is the smart move, because a sub-slab depressurization system is far easier to install while the floor and walls are still open. After any renovation that affects the structure or ventilation of the home, the guide recommends testing again the following heating season.