Do You Need a Building Permit in Ontario? The Actual List
Replacing a furnace needs no permit. Modifying the heating system does. Most of the confusion lives in pairs like that one.
In short
Under Ontario’s Building Code Act you need a permit to construct or demolish a building, build an addition, or make a material alteration to any building or structure. In practice the question is never the law — it is which side of the line your particular job falls on.
And the line runs through places most people would not guess. Replacing a furnace: no permit. Modifying the heating system: permit. Installing a sump pump: no permit. Installing a backwater valve: permit. Below is the real list, with the pairs that catch people set side by side.
Do I need a permit to replace a furnace or a window?
If you read only one section, read this one. Each row is two jobs that sound like the same job.
| No permit | Permit required | Where the line is |
|---|---|---|
| Replacing a furnace or boiler in a house | Installing or modifying the heating system | Swap versus rework |
| Installing a sump pump | Installing a backwater valve | One counts as plumbing work under the Code, one does not |
| Replacing a window in its existing opening | Enlarging or relocating the opening | Whether the structure is touched |
| Adding a hot water tank or extra cooling in a house | Modifying the plumbing system | Addition versus alteration |
| Replacing roofing material, no structural work | Anything structural under the roof | Whether framing is involved |
| Finishing a basement with no plumbing, no wall changes, no second unit | Any one of those three | Plumbing, structure, or a new dwelling unit |
| Installing cabinetry and millwork | Removing or adding a wall | Whether the box itself changes |
What work needs a building permit in Ontario?
The list below follows the City of Toronto’s own published list, last updated in July 2026. Other Ontario municipalities apply the same Building Code, but thresholds and local rules vary — always confirm with your own building department.
What work does not need a building permit?
If I do not need a permit, do zoning rules still apply?
This is the trap underneath the whole list, and the City states it plainly: even where a building permit is not required, compliance with the zoning bylaw is still required.
Zoning is a separate question from the Building Code. It governs how close to the property line you may build, how much of the lot may be covered, how tall a structure may be, and what may exist where. A shed can be permit-exempt at 14 square metres and still be illegal because it sits 30 centimetres from your neighbour’s fence.
So the honest two-part question is: do I need a building permit, and does this comply with zoning. People who ask only the first one are the ones who end up moving a structure.
Are the rules the same in every Ontario municipality?
Ontario has one Building Code, and municipalities administer it. The provincial exemption for a storage shed is 15 square metres — but Mississauga and Brampton apply a 10 square metre cut-off, and others differ again.
Which means the number you find in an article — including this one — is the starting point, not the answer for your address. One phone call to your building department settles it, and building departments answer this question all day.
What happens if you build without a permit?
The City of Toronto puts the consequences in one sentence: failing to obtain permits can result in costly construction delays, legal action, and the removal of work already completed.
That last one is the expensive part. Unpermitted work does not quietly disappear; it turns up when you sell, when an insurer asks questions after a claim, or when a neighbour makes a call. And the responsibility sits with the owner, not the contractor — the City says so directly: as the building owner, you are ultimately responsible for complying.
Red flags from a contractor
What to do next
Before you sign anything, call your municipal building department and describe the job in one sentence. It is free, it takes minutes, and they will tell you both whether a permit is needed and whether zoning is an issue. Write down who you spoke to and when.
Then compare renovation and construction companies in Ontario on Ontario24 and ask each one, in writing, who pulls the permit and whose budget it comes out of. Ontario24 is a classified directory — we help you find and compare businesses, and we do not vet them; our safety tips and our guide to choosing a contractor cover the rest of the questions worth asking.
Before you call anyone, it helps to know what this job should cost and what the next one will. What things cost in Ontario in 2026 puts 75 service prices in one table.
Frequently asked questions
It depends on the work. No permit is needed if you are only framing, insulating and finishing with no structural changes, no new plumbing and no second unit. A permit is required the moment you move a wall, add plumbing, cut a basement entrance, underpin, or create an additional dwelling unit.
No, replacing a furnace or boiler in a house does not require a building permit. Installing or modifying the heating system itself does. The same split applies to hot water tanks and added cooling: a straight replacement is exempt, reworking the system is not.
Up to 15 square metres, about 161 square feet, provided it is one storey, detached from any other structure, used only for storage and has no plumbing. Some municipalities are stricter — Mississauga and Brampton use a 10 square metre threshold, so check locally.
Only if the finished deck surface is more than 60 centimetres, about 24 inches, above the grade beside it, or if the deck forms a required exit. A low uncovered platform below that height that is not a required exit needs no building permit, though it must still comply with zoning.
Not in a detached, semi-detached or row house with a single dwelling unit, provided the opening is not moved or resized, the structural support is unchanged and no new exit is created. Enlarging or relocating an opening requires a permit, as does replacing windows in other building types.
The City of Toronto states that failing to obtain permits can result in costly construction delays, legal action, and the removal of work already completed. It can also complicate a future sale, because unpermitted work surfaces in searches and insurers may take a view on it.
No. Even where a building permit is not required, compliance with the zoning bylaw is still required. Zoning governs setbacks, lot coverage, height and what may be built where — a separate question from the building permit, and one people are caught by regularly.
Sources
The permit and exemption lists above follow the City of Toronto’s published guidance “When Do I Need a Building Permit?”, last modified 21 July 2026, which sets out common projects on each side of the line under the Building Code Act. Shed thresholds for other municipalities are those published by those municipalities. Checked 17 September 2026. Municipal requirements differ and change — this article is general information and not a substitute for confirming your specific project with your own building department. Ontario24 is a classified directory and does not issue permits, review drawings or perform construction.