Commercial Building Permits in Ontario — The Part 3 Process, Step by Step

Is Your Commercial Project a Part 3 Building?

In Ontario, the Building Code splits almost everything into Part 9 (housing and buildings of limited size — most houses and small buildings) and Part 3 (larger and high-hazard buildings) — think restaurants with many occupants, offices, retail, medical clinics, warehouses over a certain height and area, schools, and assembly buildings.

Your first step is understanding which part governs, because it drives everything: how complete the drawings must be, whether you need a P.Eng. structural package, the review timeline, and the fees. A restaurant fit-out in a strip mall might be Part 9; the same restaurant with an occupancy load pushing thresholds, or a mezzanine, can cross into Part 3.

“Nothing about a commercial permit is slower than residential — except estimating it like residential. The Part 3 threshold decides how deep the documentation goes.”

What's typically Part 3

Restaurants with larger occupancies, offices, retail, medical clinics, schools, institutions, warehouses over threshold, industrial.

What's typically Part 9

Most houses, small residential buildings, and limited-size small commercial that don't exceed Part 3 thresholds.

The Step-by-Step Commercial Permit Process

Zoning & building code pre-check

Confirm the use is permitted on the property and which Building Code part applies. Cheap to do now, expensive to discover after design.

Design & permit drawing set

Site plan, floor plans, elevations, sections, and a code compliance narrative. For Part 3, expect a full design team and complete documentation.

Structural engineering package

Part 3 commercial buildings essentially always need a P.Eng.-sealed structural package — the load path for the whole building must be shown.

Municipal submission

Complete application with drawings, forms, and fees. Some municipalities use online portals; large cities have pre-application meetings.

Review & resubmission

Expect at least one round of comments. Missing structural info is the #1 reason commercial permits stall — because it can't be waved through.

Permit issuance → construction → occupancy

Building inspections during construction, then the occupancy permit. Close-out requires the structural inspection letters.

Realistic Timelines (and Why They Slip)

You'll hear "6 to 12 weeks" from municipalities, and for a clean, complete application that's genuinely possible — but commercial reviews are routinely longer. The review clock doesn't even start properly until your application is deemed complete. The honest timeline for a straightforward commercial fit-out or new build, including documentation, review, and at least one resubmission round, is more like 3 to 6 months from "start design" to "permit in hand."

The leading cause of commercial permit delay is an incomplete structural package. Municipalities can't issue a Part 3 permit without the engineered structural design. Budget for it before you submit — it's the difference between 6 weeks and 6 months.

May Engineering Inc: The Structural Half of Your Commercial Permit

May Engineering Inc carries the engineering side of commercial projects across Ontario — the structural engineering, the site visit letters, and the coordinated permit documentation that municipalities ask for. From a restaurant fit-out with a mezzanine to a full industrial building, we produce the engineered package that moves your commercial permit forward instead of holding it back.

Starting a commercial project in Ontario? Our structural engineering services bring the P.Eng. package in at the pre-check stage — we'll confirm which code part applies and scope the exact engineering your municipality will require. Get a quote.