Do You Need a Building Permit for a Renovation in Ontario?

Most renovations that change the structure, add plumbing, finish a basement or create a new unit need a building permit in Ontario. Cosmetic work usually does not. The dividing line is not how big or expensive the job feels; it is whether the work touches structure, plumbing, sleeping accommodation or the building’s compliance with the Ontario Building Code. When in doubt, the answer is to call your municipality’s building department before work starts, because the cost of asking is nothing and the cost of guessing can be very high.

The rules come from the Building Code Act, 1992 and the Ontario Building Code, currently the 2024 edition in force since January 1, 2025. Municipalities enforce them through the building department, headed by the chief building official, which issues permits and inspects the work. A building permit is the municipality’s record that the work will meet the Code and that it gets inspected at the stages where mistakes become expensive to fix.

Which renovations usually need a permit, and which usually don’t

The lists below are a guide, not a substitute for your municipality’s own rules. Municipalities interpret and apply the Code, and local practice varies, so confirm with the building department before you book a contractor or order materials.

Two things trip people up. First, “cosmetic” means the same fixture in the same place; moving a sink a metre along the wall is plumbing work and needs a permit. Second, a finished basement is rarely just drywall and carpet. Once you add a bathroom, a bedroom, a kitchenette or a separate entrance, you are into permit territory, and the requirements for things like bedroom windows and ventilation apply. The basement finishing permits guide sets out what a basement project typically triggers.

The permit is only one of several approvals

A building permit does not stand alone. Before the building department issues one, the plans must comply with the zoning by-law made under the Planning Act, which controls setbacks from lot lines, height, lot coverage and use. If a proposed addition or deck does not fit the by-law, the owner can apply to the municipality’s Committee of Adjustment for a minor variance. That is a separate application with its own process and timeline. The zoning and minor variance guide explains how that works.

Other approvals can also apply. Properties designated under the Ontario Heritage Act, or inside a heritage conservation district, often need heritage approval for exterior changes. Lots near rivers, streams, wetlands, shorelines or valleys may be regulated by a conservation authority, whose permit is needed before building. And since 2022, the Planning Act allows most urban residential lots served by municipal water and sewers to have up to three residential units as of right, but a building permit is still required and the Building Code and Fire Code still apply.

Electrical, gas and plumbing have their own rules

A building permit does not cover everything. Electrical work goes through the ESA, gas work through a TSSA-registered contractor, and plumbing usually needs its own municipal plumbing permit with its own inspections.

• Electrical: the Electrical Safety Authority (ESA) enforces the Ontario Electrical Safety Code. Almost all electrical work needs an ESA notification of work and inspection. Anyone paid to do electrical work in a home must be a Licensed Electrical Contractor, and that contractor files the permit. A homeowner may do electrical work in their own home only with their own ESA permit; friends, relatives and handypersons without a licence may not.
• Gas: the Technical Standards and Safety Authority (TSSA) regulates fuel safety. Gas lines and gas appliances must be installed by a TSSA-registered contractor using certified gas technicians.
• Plumbing: plumbing work needs a municipal plumbing permit and inspection, and the work is done by a licensed plumber. Plumber and electrician are compulsory trades in Ontario, so paid work is done by certified tradespeople or registered apprentices.

Structural work is its own case. Removing a load-bearing wall, adding a beam or enlarging an opening needs a design by a qualified designer or engineer and a building permit. The drawings submitted for a permit must be prepared by a designer registered with a Building Code Identification Number (BCIN) in the right category, a licensed architect or a professional engineer, though an owner may prepare drawings for their own house. The guide to renovation drawings explains who can prepare what.

How the application works, and the 10 business day clock

A permit application is a package: completed forms, drawings, and whatever else the municipality asks for. Once the application is complete, the Building Code requires the municipality to issue or refuse a permit for a house within 10 business days. That period applies to a house where no dwelling unit sits above another; a house with a basement apartment falls into a longer category. Incomplete applications do not start the clock, and many first submissions are returned for more information, which adds a round of revisions before the clock runs. That is why the drawings and the scope should be settled before the application goes in.

When the permit is issued, it names inspections at stages of the work: footings and foundation, framing, insulation and air barrier, plumbing, and a final inspection, among others depending on the job. The permit card must be posted where it is visible. Covering work before it is inspected can mean opening it up again, which is the single most avoidable delay on a renovation.

A municipality may revoke a permit if work has not seriously started within 6 months of issue, or if work is suspended or discontinued for more than 1 year. If a project stalls, talk to the building department rather than letting the permit lapse.

What happens when work is done without a permit

Unpermitted work is one of the most expensive problems a renovation can leave behind. The building department can issue orders requiring the work to be exposed for inspection, corrected or removed. Work that is covered up has to be opened up, which can undo finishes and add weeks. Insurance can be affected if a loss is traced to work that was never inspected. And at resale, a buyer’s lawyer or lender may ask for proof that permits were obtained and closed, which can hold up a sale or force a price negotiation.

There is also the safety side. Structural changes without engineering, gas work without a TSSA-registered contractor and electrical work without an ESA permit are the kinds of shortcuts that injure people later. The permit system exists to catch those problems while the walls are still open.

The order of decisions before you apply

Getting the sequence right saves time and money. A practical order looks like this:

1. Define the scope in writing: what is being built, moved or removed, and what finishes are included.
2. Check zoning and other applicable law early, before design is finalised, so a variance application does not arrive as a surprise.
3. Have drawings prepared by the right designer or engineer for the work involved.
4. Confirm which permits and approvals are needed (building, plumbing, ESA, conservation authority, heritage), who is filing each one, and that any gas work goes to a TSSA-registered contractor.
5. Request utility locates through Ontario Dig Authority (formerly Ontario One Call) before any digging. It is free, required by law, and must be requested at least 5 business days before digging.
6. Hire the contractor under a written contract, and agree who pulls which permit.

That last point matters. The building permit is usually the homeowner’s application, but the contractor often prepares and files it on the owner’s behalf. Whoever files it, the owner remains responsible for the permit being in place and the inspections being called. Put it in the contract. The step-by-step renovation planning guide covers the contract and scheduling side in more detail.

What goes wrong

• Assuming cosmetic means no permit. Moving a fixture, adding a wall or creating a bedroom changes the permit picture. Ask before demolition.
• Applying with incomplete drawings. The 10 business day clock only starts on a complete application, and resubmissions are common. Settle the design first.
• Covering work before inspection. Framing, insulation and plumbing are inspected before they are closed in. A missed inspection means opening the wall again.
• Forgetting the separate electrical and plumbing permits. A building permit does not cover them, and each has its own inspection.
• Skipping the zoning check. A permit will not be issued if the plans do not meet the zoning by-law, and a minor variance takes time.
• Letting a permit lapse. Work must seriously start within 6 months, and a long suspension can lead to revocation.
• Not testing older materials. Asbestos was used in Canadian homes mainly before 1990, and homes built before 1960 probably contain lead-based paint. Have suspect materials tested before demolition, and do not disturb vermiculite insulation.
• Skipping the radon test. Health Canada’s guideline is 200 Bq/m³, tested with a long-term detector for at least 3 months (91 days). Finishing a basement is a good moment to test and, if needed, install a mitigation system.
• Assuming Tarion covers it. Tarion’s warranty covers new homes built by licensed builders; it does not cover renovations or additions to an existing house. For those, the protection is the written contract, the contractor’s own warranty and insurance.

Questions to ask before work starts

Ask the building department: does this scope need a permit, what drawings are required, and which inspections will be called at which stages? Ask the contractor: who files the building, plumbing and ESA permits, and are those costs in the contract? Then put the answers in the written contract that the Consumer Protection Act, 2002 requires for home renovation work, so that responsibility for each permit and inspection is on paper before the first wall is opened.

An addition or a major improvement can also change a home’s assessment by MPAC, which affects property tax.