Basement finishing

Ottawa is a full-basement city. Almost every house built here since the war has one, and finishing it is the cheapest square metre a homeowner will ever add. It is also the renovation most likely to be done badly, because the expensive part is invisible and the tempting part is the drywall.

Step one: check for moisture, cracks, staining, grading and downspout problems before finishing a basement. Ask for any active leak to be diagnosed and priced separately before it is concealed.

Step two: the permit. The City has a permit process for finishing basements; requirements for bedrooms, structure, plumbing and separate units depend on the scope. Permit documents in Ontario generally have to be prepared by a designer registered with the Ministry and holding a BCIN, unless you are designing work on a building you own, or the designer is an architect or a professional engineer (the designer qualification rules).

Step three: moisture control and insulation. The order matters. A dimpled membrane or rigid insulation goes against the concrete so the wall can dry, then the framing stands off it. Spray foam directly to a sound, dry foundation wall is common here and works. What fails is a vapour barrier on both sides of an assembly, which traps water in the middle.

Step four: frame and complete rough-ins only after confirming the required clearances and inspections for the proposed basement use with the City and a qualified designer.

Step five: check whether the proposed bedroom needs a window or other escape route under the applicable Building Code provisions. Ask the City and a qualified designer before pricing foundation openings.

How long it takes. A straightforward rec room in a dry basement is four to seven weeks. Add a bathroom and it is seven to ten, because the drain has to be broken into the floor slab and inspected. Add an egress window and a bedroom and you are at eight to twelve weeks.

For a basement quote, specify finished area, moisture repairs, insulation, bathroom plumbing, electrical work, windows and permit responsibility. Ask for a separate price for each optional room or system.

HST, and the rebate that almost never applies. Taxable renovation services supplied by an HST registrant in Ontario generally carry 13 per cent HST. Ordinary work does not generally qualify for the GST/HST new housing rebate. The GST/HST new housing rebate only reaches a substantial renovation, which the CRA defines as removing or replacing 90 per cent or more of the interior of an existing house, and it states specifically that renovating a basement does not meet that definition (CRA RC4028).

What the warranty does and does not cover. The Tarion new home warranty is for newly built homes from a licensed builder, with one, two and seven year periods. It does not cover a renovation of an existing home, and it explicitly excludes work and materials supplied by the homeowner and alterations the homeowner makes (Tarion exclusions). Review any written contractor warranty, the applicable permit and inspections, and the statutory holdback; each addresses a different risk.

Who should do the work. General contracting is not a licensed trade in Ontario. Two things inside the job are: electrical and plumbing are compulsory trades, so ask to see the certificate of qualification, and electrical work needs an ESA notification and inspection. Anything structural, such as dropping the floor or cutting the foundation wall for an egress window, should be designed by a professional engineer you can check in the PEO directory. Confirm WSIB status too, since coverage is compulsory in construction and the exemption for work retained directly by the occupant does not extend to subcontractors (WSIB).

What to ask before you hire. Who prepares and signs the permit drawings, and what is their BCIN. Does the price include the permit and the inspections. What happens if moisture is found after demolition. Who does the electrical and plumbing, and are they certificate holders. What is the written warranty, how long, and is it transferable. Ask how the ten per cent statutory holdback will be retained and released under the Construction Act, including the 2026 annual-notice rules (Construction Act holdback in 2026).