Projects That Always Require a Building Permit

The Ontario Building Code sets a minimum standard, and municipalities can only be more restrictive — never less. The following project types require a building permit everywhere in Ontario, without exception:

• ✓ Additions — Any increase to the footprint or height of an existing structure, including second-storey additions, rear additions, side additions, and garage conversions to living space.
• ✓ Structural changes — Removing or modifying load-bearing walls, changing the structural load path, underpinning a foundation, or any work that affects the structural integrity of the building.
• ✓ New construction — New homes, garden suites, detached garages, and any new structure intended for human occupancy or with a footprint over the exempt threshold.
• ✓ Basement conversions and secondary suites — Converting an unfinished basement into living space, or adding a legal secondary unit, always requires a permit regardless of scope.
• ✓ Plumbing and HVAC alterations — Adding a new bathroom, relocating a drain stack, installing forced-air heating, or making any change to the mechanical or plumbing systems beyond like-for-like replacement.
• ✓ Decks above the exempt threshold — In most GTA municipalities, decks over 10 m² (approximately 108 sq. ft.) that are attached to the house or raised more than 600mm above grade require a permit.
• ✓ Demolition — Full or partial demolition of a structure requires a permit. This includes removing a chimney, tearing down a load-bearing wall, or demolishing an attached garage.

Projects That Generally Do Not Require a Permit

The following types of work are typically exempt from building permit requirements across Ontario. Note the word “typically” — there are always exceptions at the municipal level:

• ✓ Painting and interior finishes — Paint, wallpaper, new flooring, tile replacement, and other cosmetic surface work do not require a permit.
• ✓ Cabinet and millwork replacement — Replacing kitchen or bathroom cabinets without moving plumbing or altering the structure is generally exempt.
• ✓ Like-for-like appliance replacement — Swapping a furnace, water heater, or air conditioner for an equivalent unit in the same location, without ductwork changes, is generally exempt.
• ✓ Small accessory structures — Garden sheds and detached structures under 10 m² (approximately 108 sq. ft.) that are not used for human occupancy are typically exempt — but placement must still comply with zoning setbacks.
• ✓ Fencing — Most residential fencing does not require a building permit, but fences must comply with the municipal fence bylaw governing height and materials. Pool enclosures are a significant exception and almost always require a permit.

The Grey Area — Projects That Depend on Your Municipality

This is where most permit surprises happen. The following project types sit in a grey zone where the answer genuinely depends on which municipality your property is in:

Deck size thresholds vary significantly. While 10 m² is the provincial baseline for exemption, some municipalities apply more restrictive thresholds. A deck that is permit-exempt in Newmarket may require a permit in Oakville. The height-above-grade trigger (600mm in the OBC) also varies locally — some municipalities lower that threshold further.

Interior renovations involving plumbing. Replacing a toilet or faucet in the same location is typically exempt. Adding a wet bar, relocating a bathroom, or roughing in for a future bathroom crosses into permit territory. The line is whether you are extending the plumbing system or simply servicing it.

Accessory structures on smaller lots. The 10 m² exemption applies to the structure itself, but the lot coverage calculation at the municipal level may still restrict how much you can build even if a permit is not required. Building permit-exempt and zoning-compliant are two different things.

What Happens If You Skip the Permit

This question comes up constantly. The honest answer is that consequences range from inconvenient to severe, and they do not always show up immediately — which is why some people convince themselves the risk is manageable. It is not.

Stop-work orders are issued by municipal bylaw officers when unpermitted construction is discovered. Work stops immediately. In active construction, this can mean trades sitting idle while the permit situation is resolved — at your cost.

Fines under the Building Code Act can reach $50,000 for individuals and $500,000 for corporations. Municipal penalties apply on top of these provincial minimums. Hamilton, for example, doubles the permit fee as a penalty for any work started before a permit is issued.

Orders to remove non-compliant work. If work was done without a permit and cannot be brought into compliance retroactively, the municipality can order it removed. That means tearing out a finished basement or demolishing an addition.

Title compliance orders are placed on the property and show up in title searches. They affect your ability to sell, refinance, or borrow against the property. Buyers’ lawyers flag them. Lenders reject applications. They do not go away until the permit situation is resolved.

Insurance claim denial. If you make an insurance claim for damage to unpermitted work — a fire in the unpermitted basement apartment, water damage from the addition that was never inspected — your insurer may deny the claim. Insurance policies typically exclude damage to structures built without required permits.

How to Find Out for Sure

The fastest and most reliable way to confirm whether your project requires a permit is a five-minute phone call with the right information in hand: the property address and a plain-language description of what you want to do.

You can call your municipality’s building department directly. They will tell you whether a permit is required. The limitation is that they will not tell you whether your project is feasible from a zoning perspective — that is a separate question that requires a zoning review.

If you want both questions answered at once — permit requirement and zoning feasibility — GTA Permits offers a free initial consultation. We look up the zoning, confirm the permit requirement, and flag any complications (conservation authority overlap, heritage designation, committee of adjustment needs) before you commit to a design. It takes one call. You get a straight answer.

If you already know a permit is needed and you are ready to get started, see our residential permit services page for a full breakdown of what the process involves, or visit our FAQ page for answers to the most common questions we receive.