Cost of a Basement Renovation in London, Ontario, 2026 Breakdown

By Absolute Home Creations · September 22, 2026 · Basements & Attics

Absolute Home Creations has finished rec rooms, in-law suites, and legal basement apartments across London, Hamilton/Burlington, and Kitchener-Waterloo for 35+ years. We pull permits, coordinate inspections, and design to Ontario Building Code, as a RenoMark and LHBA contractor with BBB accreditation.

What a basement renovation costs in London in 2026

London prices sit below typical Greater Toronto Area quotes for the same scope. Local 2026 contractor ranges for an open, dry, unfinished basement of about 700 square feet look like this (Power House Construction, 2026 London basement cost guide):

Canada-wide, HomeStars puts a full remodel between $30,000 and $175,000, with a mid-range living area plus bathroom often $60,000 to $90,000 on about 600 square feet, and $50 to $150 per square foot across all scopes. London’s trade rates pull the local floor of that band down.

Per-square-foot math is a first gut check, not a quote. A bathroom, kitchen, or egress window costs almost the same in a 500 sq ft basement as in a 1,000 sq ft one, so the per-foot figure falls as the space grows even while the cheque gets larger.

Where the money actually goes

Finishes are visible. Trades are the bill.

A rec room needs a framer, electrician, drywaller, and painter. Add a bathroom and a plumber arrives, the slab may get cut, and the inspection list grows. Common 2026 adders in Southwestern Ontario:

• Three-piece bathroom: about $15,000 to $30,000, depending on an existing rough-in and how far the drain has to run (Power House Construction). Canada-wide, HomeStars lists three-piece basement bathrooms around $15,000 to $22,000, with half-baths $8,000 to $12,000.
• Egress window for a bedroom: $2,500 to $8,000 per opening (excavation, well, drainage, sometimes a lintel).
• Separate entrance or walkout: $5,000 to $16,000.
• Electrical panel upgrade: $2,000 to $5,000 in many Canadian cities (HomeStars); older London homes on 60-amp service often need this before a finished basement load is safe.
• Extending forced air: $1,500 to $3,500.
• Spray foam at rim joists: $600 to $1,200. That is where most basement air leaks.
• BCIN designer drawings: $1,500 to $4,000.
• Underpinning for headroom: $90 to $150 per sq ft locally, or $30,000 to $80,000 on many Canadian jobs (HomeStars). Underpinning can turn a $45,000 rec room into a six-figure project. Talk about ceiling height before you pick tile.

Starting condition matters more than paint. HomeStars notes a $20,000+ gap between a bare concrete basement and one that already has framing, insulation, and plumbing. Gutting a 1990s finish that was never permitted often costs more per square foot than finishing a clean, open basement.

What London housing stock does to a quote

Old North, Woodfield, Wortley Village, and older East London houses often hide 60-amp panels, leftover knob-and-tube, galvanised supply lines, and low joists crossed by ducts. A walkthrough misses most of it. Demolition does not.

Post-1980 subdivisions (Byron, Masonville, Oakridge, Stoneybrook, Summerside) usually start better: poured foundations, higher clear heights, modern panels, and sometimes a bathroom rough-in already in the slab. A rough-in that lands where you actually want the bathroom can take several thousand dollars off the quote.

Southwestern Ontario winters also punish shortcuts. Condensation on cold foundation walls, spring melt against window wells, and humidity from laundry all show up after the drywall is painted. Insulation, vapour control, and drainage belong in the first week of the job, not as a callback.

Do you need a permit to finish a basement in London?

Yes, for almost any real basement project. The City of London requires a building permit before you start:

• Basement finishing that creates rooms or living space
• A basement apartment (Additional Residential Unit)
• Excavating for headroom
• A below-grade entrance or walkout
• Underpinning
• Adding, removing, or relocating plumbing fixtures
• New or enlarged windows
• Interior alterations and HVAC work

Painting, damp-proofing, and swapping a fixture in the same location generally do not need a permit. Framing rooms, new electrical, new plumbing, and bedrooms do.

Work that starts before the permit issues can trigger extra fees under the City’s building by-law, a stop-work order, problems at resale, and insurance trouble on a finished basement with no permit history. A RenoMark contractor pulls the permit and stays for the inspections.

What the City of London charges in 2026-27

Figures reported from Schedule A of Building By-law B-7 for 1 March 2026 to 28 February 2027 (Power House Construction summary, citing the City fee schedule):

A 700 sq ft basement is about 65 m². At $3.68/m² that is roughly $239, so the minimum $260.37 applies. A 1,000 sq ft finish is about 93 m², or roughly $342. Most London basement finishes pay $260 to $400 in building permit fees, not the four-figure Toronto number many national guides quote. The clock starts only when the City deems the application complete. Missing drawings are why some permits “take six weeks.”

Electrical work also needs an ESA permit. Plumbing inspections sit on top of the building permit.

Ontario Building Code items that move cost

You do not need to memorize the Code. You do need to budget for it.

• Ceiling height. Habitable rooms need adequate clear height. Ducts that hang too low force soffits, a dropped ceiling, or underpinning.
• Egress. Any basement bedroom needs a proper egress window (size, opening, well, and drainage) or a door to the exterior.
• Insulation and vapour control. Foundation walls in this climate need a Code-compliant assembly, not poly stapled over damp block.
• Smoke and CO alarms. Interconnected devices are required; suites need more.
• Stairs, guards, and headroom on the run down.
• Fire separation and a second means of egress if you create an Additional Residential Unit.

The City of London Additional Residential Units page is the starting point if the basement will be a self-contained dwelling. That is a different project from a family rec room. Week 5 of this content series covers legal basement apartment requirements in more depth.

HST applies to renovation labour and materials. Build 13% into the total, plus a 10-15% contingency for hidden slab, panel, or moisture work. HomeStars also flags contractor management of 10-20% on trade costs when a general contractor runs the job. That fee is how inspections, sequencing, and warranty actually get owned.

A practical process that keeps the budget honest

1. Moisture first. If the walls weep or the slab is damp, stop. Waterproofing and grading belong before studs.
2. Measure headroom and services. Furnace, duct mains, sanitary, and the panel dictate the plan more than Pinterest.
3. Decide: family space or legal suite. Mixing the two halfway (a kitchenette with no fire separation) is the expensive mistake.
4. Drawings and permit. BCIN design, City of London building permit, ESA, plumbing.
5. Rough-ins and inspections. Framing, electrical, plumbing, insulation, then close-in.
6. Finishes. Flooring that tolerates concrete (luxury vinyl plank is the London default), a bathroom that can be cleaned, lighting that makes a basement feel like a main floor.

Absolute Home Creations designs basement rec rooms, legal apartments, in-law suites, and attic conversions with egress windows and permits handled. Many of the same homeowners also refresh the kitchen or bathroom on the main floor in the same year; sequencing those jobs saves mobilization cost.

Get a written basement quote

Email a few details (address, approximate size, bathroom or not, suite or family space) to inquiries@absolutehomecreations.com. A person from the company replies, usually the same day. No forms, no call centre.

We serve London, Hamilton/Burlington, and Kitchener-Waterloo/Cambridge.