Ask three contractors what a basement costs and you will get three very different answers. Published prices in Ontario run from $35 to $130 a square foot, which on a 700 square foot Bowmanville basement is anywhere from $24,500 to $91,000. That gap is not us being vague. It is the market genuinely not agreeing with itself.
Bowmanville is two towns in one for this kind of work. The streets around the downtown core were built between 1850 and 1900, mostly Victorian, and that is where ceiling height, old wiring and asbestos era materials are part of the conversation. West of there, Brookhill is a modern community of detached and semi detached homes with full height basements, and Clarington approved the Soper Springs plan for north Bowmanville in April 2026, so the newest stock in town is only now going up.
These are the prices other companies publish, not ours. We show you where each one comes from so you can judge it yourself.
| Scope | Published range | What that range rests on |
|---|---|---|
| Basic finish, no bathroom, about 700 sq ft | $24,500 to $91,000 | Contractor estimates spanning $35 to $130 per sq ft |
| Adding a three piece bathroom | Add $15,000 to $35,000 | Contractor estimates, a spread of nearly six times |
| Legal second unit, permits included | $50,000 to $180,000 | Contractor claims. Building permit records for basement suites declare a median nearer $25,000 |
| Lowering the floor or underpinning | $30,000 to $100,000 | 17 permit records for underpinning with finishing, median $60,000 |
Pulled from published Ontario contractor prices and municipal permit records on 1 August 2026. We show you the full spread instead of picking an average, because the sources really do disagree by up to four times, and two of the bigger ones turned out to be publishing the same numbers as each other. Your price comes from a free visit, fixed, with HST already in it.
Clarington charges about $509 on a 1,000 square foot basement, with a minimum under a hundred and forty dollars. That is well below Toronto and less than half what Orangeville charges. When a quote shows three or four thousand for permits, almost all of it is drawings and engineering.
An interest free loan of up to three thousand dollars for an approved backwater valve and sump pump, paid back on your quarterly water bill over three years. Existing homes only, and you need to have actually had a sewer backup. If the basement has taken water, this comes before the drywall.
Clarington does not make you file separately. Once the building inspector grants occupancy the added unit is considered registered. Up to two are allowed in most places, though parts of Clarington sit on the Oak Ridges Moraine where it can drop to one or none.
If the property is on private servicing you need a permit from the Durham Region Health Department before the building permit can be issued. It is not difficult, it just has to happen in the right order, and it is the kind of thing that quietly adds weeks if nobody mentions it.
For a rental unit in a house that is already built, the rule is 6 feet 5 inches across the space, not the 7 feet people quote at you. Plenty of basements written off as too low actually pass. It takes two minutes with a tape measure to find out.
If the home went up before 1990, the law puts this on you as the owner rather than on your contractor. You have to have the materials checked and give the report to anyone quoting. It sounds like a hassle. It is far cheaper than finding it halfway through the job.
Give us the address and a time that works for you. No sales pitch and no waiting on a callback.
Ceiling height, damp, wiring, where the drain sits, and what the rules allow for what you actually want. About 45 minutes.
Written down, HST included. If there is anything we cannot price without opening a wall, we say so next to the number instead of hiding it.
One free visit, one fixed price, HST included. No sales pitch and no callback loop.
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