Usually needs a permit
- Finishing a basement into living space, and excavating to increase headroom.
- Adding a second unit or basement apartment.
- Removing or altering a load-bearing wall, adding a beam, changing the roof structure.
- An addition, a new garage or an accessory building over ten square metres.
- A deck above the height your municipality sets. Mississauga, for example, requires a permit for a deck more than 0.61 m (2 ft) above grade.
- New plumbing, a new bathroom, a new foundation or underpinning.
Usually does not need a permit
- Painting, flooring, cabinets and cosmetic finishes.
- Replacing fixtures in the same location.
- Damp-proofing an existing basement without changing the structure, per Mississauga guidance.
- Small ground-level decks below the municipal height threshold.
These are common examples, not a legal list. Confirm with your own municipality’s building department before starting; many publish a “when a permit is required” page.
Who applies
The owner is responsible for the permit, but contractors routinely apply on the owner’s behalf. Decide this in writing before work starts, along with who books inspections. Keep the permit and the final inspection record: buyers, insurers and lawyers ask for them later.
What happens if you skip the permit
- A stop-work order, and an order to uncover or remove finished work for inspection.
- Fines under the Building Code Act. Published figures for individuals go up to $50,000 for a first offence and $100,000 for a subsequent offence; corporate amounts quoted by municipalities vary, so check the Act and your municipality.
- Problems at resale, and disputes with insurers after a loss connected to unpermitted work.
Electrical work is separate
A building permit does not cover electrical work. Electrical installations must be done by an ECRA/ESA licensed electrical contractor, who files a notification with the Electrical Safety Authority.
Frequently asked questions
An inspection checks compliance with the Ontario Building Code at specific stages. It is not a review of finish quality or of your contract.
Municipalities can issue a permit for existing work, but they may require parts of it to be opened up for inspection, and corrections can be expensive.
Fees are set by each municipality and depend on the project. Toronto’s published fee for a deck permit is $214.79 effective 1 January 2026; larger projects are priced by area or value.
Sources
- Ontario.ca, Citizen’s guide to land use planning: building permits – ontario.ca
- Ontario.ca, Add a second unit to your house – ontario.ca
- City of Mississauga, When a building permit is required – mississauga.ca
- City of Toronto, Decks and porches permit guide, fee effective 1 January 2026 – toronto.ca
- Electrical Safety Authority, Hiring an electrician or contractor – esasafe.com
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