Which Home Renovations Need a Building Permit in Ontario

This article is general information, not a substitute for your municipality's rules. Thresholds and requirements can change; confirm with your local building department before you start.

The most expensive renovation mistake is skipping a permit you actually needed. Here is the good news, though: in Ontario, what needs a permit is more standardized than most people assume. The thresholds come from the province-wide Ontario Building Code, and they are strikingly consistent from city to city. What varies is the zoning layer (what your municipality allows on your specific lot) and local enforcement, and you clear both when you apply. So the honest one-line rule is this: the thresholds are province-wide, but the permit is issued and enforced by your municipality alongside its own zoning, so confirm with your local building department before you start.

What generally needs a building permit

• Structural changes. Adding or removing a load-bearing wall to change room sizes or layout.
• Additions and new structures over 10 square metres, including finishing work that changes the building.
• A basement apartment or second unit. This always needs a permit for fire separation, exits, alarms, ceiling height, and egress windows, even though provincial law now allows up to three units as-of-right on many lots. As-of-right zoning does not remove the permit requirement.
• Finishing a basement, if the work involves structural changes, new or moved plumbing or heating, a new basement entrance, or a second suite.
• Decks more than 60 centimetres (24 inches) above the ground.
• New or enlarged window and door openings where there was none before, or relocating one.
• Demolition of all or part of a building.
• Plumbing and heating or HVAC changes, such as adding plumbing or installing new ductwork or a furnace.
• A detached garage or accessory building over 10 square metres, and a shed of 15 square metres or more. Note the wrinkle: any attachment to a building, or any plumbing, triggers a permit regardless of size.

What generally does not

• Painting, flooring, and kitchen cabinets (same layout, no plumbing moved).
• Re-shingling a roof, like-for-like, with no structural work.
• Replacing a window or door in the same existing opening.
• Swapping plumbing fixtures, and minor additions like a gas fireplace, a hot water tank, or a humidifier.
• Insulation, basement waterproofing, and a sump pump.
• A small storage shed under 15 square metres, as long as it is one storey, detached, storage-only, and has no plumbing.
• Fences do not need a building permit, but they must follow your municipality's fence bylaw (height limits vary by city), and a pool enclosure is a separate required permit.

The electrical wrinkle everyone misses

Here is the one that trips people up: electrical work is not covered by your building permit. It runs on a completely separate track through the Electrical Safety Authority (ESA), which requires a "notification of work." In the ESA's own words, a building permit "isn't the same as filing an electrical notification. You may need both." A homeowner can file the ESA notification for work in their own home; anyone you hire to do electrical work must be a Licensed Electrical Contractor. (Gas and fuel-burning appliance work is similar, regulated separately by the TSSA and requiring a licensed technician.)

So a basement renovation can easily need a municipal building permit and an ESA electrical notification. Check both.

Why skipping a permit is a bad bet

It is not a technicality:

• Fines. Building without a required permit is an offence under the Building Code Act, with fines up to $50,000 for a first offence and $100,000 for subsequent offences for an individual (far higher for corporations).
• Stop-work and comply orders. The city can halt your project and require you to apply for the permit and bring the work to code.
• Undoing the work. To inspect concealed work, an inspector can require you to open finished walls, and non-compliant work may have to be redone at your expense.
• Insurance risk. If unpermitted work contributes to a loss, a fire from DIY wiring, a flood from a moved drain, your insurer may deny the claim.
• Resale headaches. Unpermitted work complicates a sale, from disclosure to a buyer's financing to demands for a retroactive permit.

The practical move

When you are not sure, a five-minute call to your municipal building department settles it before you spend a dollar. And keep the permit and the final inspection with your home documents; it is exactly the paperwork that proves the work was done properly when you sell.

Frequently asked questions

Do I need a permit to finish my basement? Often yes. If the work includes structural changes, new or moved plumbing or heating, a new entrance, or a second unit, you need one. A purely cosmetic finish may not, but confirm with your municipality.

Is the deck threshold really 60 centimetres? Yes. A deck more than 60 centimetres (24 inches) above the ground needs a building permit in Ontario.

Does a building permit cover electrical work? No. Electrical is a separate track through the Electrical Safety Authority, and you may need both a building permit and an ESA notification.

What happens if I skip a required permit? Fines, stop-work orders, being ordered to open up or redo the work, possible insurance denial, and problems when you sell. It is rarely worth the risk.

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