Most homeowners in Newmarket learn about permits at the worst possible moment: after the drywall is up, when a buyer's lawyer asks for the paperwork, or when an inspector knocks because a neighbour called. The Ontario rule is narrower than people expect and far wider than they hope. It has nothing to do with how big the job feels or what it cost. It turns on whether you are altering the building itself. Here is where that line actually falls, the four projects homeowners misjudge most often, and how to check your own address before you buy material.
The short answer: what triggers a permit in Ontario
Ontario does not publish a list of renovations that need permits. It sets a test, and that test sits in one statute applying everywhere in the province. Once the test is clear, most hard cases answer themselves.
The Building Code Act test, and why "minor" is not the standard
Section 8 (1) of the Building Code Act says no person shall construct or demolish a building unless a permit has been issued by the chief building official. The Act defines construct as doing anything in the erection, installation, extension or material alteration or repair of a building. Material alteration is the phrase that catches people. A homeowner reads it as major. A building department reads it as any change to structure, fire separations, plumbing, heating or the building envelope, however small the invoice.
Permits are issued by your municipality, not the province
The Code is provincial. Enforcement is not. Your permit is reviewed, issued and inspected by the building department of the town you live in, and that department applies its own zoning by law, fee schedule and exemption thresholds. Two identical decks, one in Newmarket and one across a municipal boundary, can land on opposite sides of the line.
The Town of Newmarket asks for roughly 10 to 15 working days to review a complete building permit application and say whether the permit will be issued.
Town of Newmarket, 2026. Building and Renovating
Structural changes: the case homeowners get wrong most often
This is the one that costs most to unwind. Interior demolition feels like the least regulated part of a renovation, and it is the most likely to need stamped drawings.
Removing a wall, and how to tell if it is load bearing
A wall carrying floor joists, a roof load or another wall above it is load bearing, and removing it is a structural alteration that needs a permit. You cannot settle this by knocking on drywall. Check these:
- Joists above run perpendicular to the wall, not parallel with it
- A beam, post or column in the basement sits below the same line
- The wall stacks over another wall and runs down to the foundation
- The wall sits near the centre of the house, where the span breaks
Where any of those hold, treat the wall as structural until a designer confirms otherwise.
Why a new beam needs drawings stamped by an independent professional engineer
Take a load bearing wall out and the load still has to reach the ground. That means a beam, posts, and a load path down to footings. Engineer is a protected title in Ontario under the Professional Engineers Act, and the Building Code Act directs the chief building official to refuse a permit where that Act requires an engineered design and the drawings do not carry one. We arrange a licensed engineer to stamp the drawings.
Underpinning and lowering a basement floor
Underpinning, bench footings and any excavation below the existing foundation are structural by definition. They are always permitted work, always designed by a third party engineer. The same applies to cutting a new door through a foundation wall.
Decks, porches and sheds: where the height and area thresholds sit
Outdoor work is where published thresholds actually exist, which makes it the easiest category to check and the easiest to misread, because the numbers belong to your municipality.
The deck height rule and how municipalities apply it
Newmarket publishes the test plainly. A deck needs a building permit if it is larger than 10 square metres, if it is attached to the home, or if it stands 600 millimetres above grade, roughly 24 inches. A freestanding deck under 10 square metres and close to the ground does not. Attached catches people, because ledger bolts into the rim joist make the deck part of the building however low it sits.
Sheds and accessory buildings under the area threshold
Newmarket allows a structurally independent detached building of 15 square metres, about 161 square feet, with no plumbing, without a permit. Go over that area, run a sink to it, or fasten it to the house, and a permit applies.
Zoning setbacks can stop a deck a permit would otherwise allow
Zoning by laws govern where a structure may sit: distance to rear and side lot lines, lot coverage, height, and easements crossing your yard. A shed small enough to skip a permit still has to respect the setback. Where it cannot, the route is a minor variance through the Committee of Adjustment, which takes months.
Basement apartments: the permit, the fire separation and the second unit rules
A basement apartment is not a finished basement with a fridge in it. It is a second dwelling unit carrying three approvals, not one: building, electrical, registration.
Ceiling height, window and egress requirements that decide feasibility
Height and light settle feasibility before anything else. Ontario's guide for second units sets the minimum ceiling height in a basement unit at 1.95 metres, roughly 6 feet 5 inches, across the whole required floor area. Window area is a share of floor area: 5 per cent for living and dining rooms, 2.5 per cent for bedrooms.
Where the only exit runs through the other unit, a second means of escape is required: a basement escape window with an unobstructed opening of at least 0.38 square metres, no openable dimension under 460 millimetres, and a sill no higher than 900 millimetres above the floor.
Fire separation between the units is the other gate. The province describes a 30 minute separation, reduced to 15 minutes where the house has interconnected smoke alarms throughout. Read the provincial second unit guide first.
Registration with the municipality is separate from the building permit
The building permit proves the unit was built to Code. Registration tells the Town it exists. Newmarket has required additional residential units to be registered since 2013, charges a one time fee of $268.93, and adds a B to the unit address so responders know two households live inside.
Finishing a basement or renovating without moving anything
The comfortable belief is that permits are for additions. In practice, finishing an unfinished basement almost always needs one, because finishing means framing new walls, forming rooms, altering heating distribution, adding circuits and usually adding a bathroom. Every one of those is a material alteration, and none of them moves an exterior wall. What genuinely sits outside a permit is a short list.
Replacing a window or door at the same size in the same opening, repairing a deck, porch, roof or chimney, waterproofing a basement where no plumbing is involved, and swapping a furnace with no building alteration all sit outside. Cut a new opening and you are back inside. Before you apply, have these ready:
- The survey or site plan for the property, and its current zoning designation
- Whether the lot falls within a conservation authority regulated area
- Drawings to scale, in unlocked black and white PDF, dated in the title block
- Schedule 1 designer information, where an independent architect or professional engineer is not taking design responsibility
- Which trades will pull their own permits, and under whose licence they work
- The inspection stages the permit will list, and who is calling them in
The current Building Code is O. Reg. 163/24, which adopts the National Building Code of Canada 2020 with Ontario amendments. Work permitted before 2025 may still sit under the older regulation, which matters when you are legalising something old. Every job in the renovation services we take on starts with this check.
What it costs to skip the permit, and how to fix work already done
The fine is rarely the biggest number. Remediation is. A building official who finds unpermitted work can issue an order not to cover under section 13 of the Act, or a stop work order under section 14, and finished surfaces come back off so the framing, wiring and fire separations behind them can be inspected.
The quieter cost lands at the sale. A purchaser's solicitor asks for permits and final inspections on visible work, insurers ask the same questions after a claim, and an unregistered basement unit can be difficult to insure as a rental. None of that is hypothetical. It is the ordinary search run on almost every resale in York Region.
Work already done can usually be legalised. It begins with a permit application for existing construction, drawings showing what is actually there rather than what was intended, and selective openings so an inspector can verify what sits behind the drywall. Where the work is structural, a third party engineer reviews and stamps it. That route is slower than permitting the job at the start, and far cheaper than discovering the problem on a closing date.
