Permits 101 · 7 min read · Last updated
A new below-grade entrance — a separate side door, a walk-up stairwell, or a full walkout — is one of the highest-value renovations in Ontario right now, because it is usually the key to a legal basement apartment. It is also structural work on your foundation, which means a building permit is always required. Here is what approval actually involves.
What counts as a below-grade entrance?
- Side or rear walk-up entrance: an excavated exterior stairwell against the foundation, leading down to a new door cut into the basement wall — the most common configuration in urban lots.
- Walkout basement: on a sloped lot, a full-height door at grade in the rear foundation wall, often with enlarged windows beside it.
- Enlarged or lowered entrance: converting an existing basement window or shallow entry into a code-compliant door, or lowering an existing stairwell.
All three touch the foundation, and none of them fall under any small-project permit exemption — the 10 m² rule that can exempt a tiny detached deck or shed has no equivalent here.
Why a permit is always required
- You are cutting a structural wall. The foundation carries the house; a new opening needs an engineered lintel or beam sized for the loads above it.
- You are excavating beside the footings. Digging a stairwell pit next to the foundation risks undermining it — the design has to respect the footing's bearing zone, and deeper entrances can require underpinning.
- Water has to go somewhere. A below-grade stairwell is a sump in waiting: the design needs a drain tied into the weeping tile or storm system, plus waterproofing where the wall is opened.
- Exit and egress rules apply. If the entrance serves a dwelling unit, stair geometry, guards, landings, door swing and headroom all have prescribed limits in the Building Code.
Rule of thumb: if a project involves touching the foundation wall — even “just widening a window” — assume a permit and an engineer's involvement before anyone quotes you a price.
Zoning: where the stairwell is allowed to go
Before the structural review, the location has to clear the zoning by-law. Most by-laws regulate how far a below-grade stairwell may project into required side and rear yards, and many older urban lots have side yards too narrow to fit a compliant stairwell at all — which pushes the entrance to the rear yard or, on corner lots, the flankage side. Several municipalities (including Toronto) have loosened these rules in recent years to make basement-suite entrances easier, but the numbers are lot-specific: check your zone's standards or get a zoning review before the design is drawn. A stairwell that violates a setback needs a minor variance — months, not days.
The basement apartment connection
Ontario now requires municipalities to allow additional residential units on most residential lots — typically up to three, such as a main dwelling, a basement suite and a garden suite. A separate below-grade entrance is what makes a basement suite practical: private access for the tenant, cleaner separation between units, and simpler compliance with the code's exit requirements for the new unit. If a second suite is your end goal, permit the entrance and the suite together — the reviews overlap, and one application avoids re-opening finished work.
What the application includes
- Site plan showing the stairwell location and distances to lot lines.
- Structural drawings: the opening size, the engineered lintel or beam specification, and any underpinning details — commonly designed and stamped by a professional engineer.
- Section through the stairwell: stair rise/run, headroom, guard height, landing, drainage, frost protection and waterproofing.
- Floor plan of the basement showing what the door serves (especially if a second unit is part of the scope).
What it costs
Illustrative planning ranges — actual numbers depend on depth, soil, access and your municipality's current fee schedule:
| Item | Ballpark |
|---|---|
| Building permit fee | A few hundred dollars (see how fees are calculated) |
| Structural engineering & drawings | Roughly $1,500–$4,000 |
| Construction — walk-up side/rear entrance | Commonly $15,000–$50,000+ (excavation, cut, lintel, stairs, drainage, door) |
| Full walkout conversion | Higher — grading and retaining work add cost quickly |
Tight lot access (hand-digging instead of a mini-excavator), deep frost footings, and underpinning are the three factors that push quotes toward the top of the range.
How long it takes
As residential work, a complete application falls under Ontario's 10-business-day review window — see how permit timelines really work. Realistic end-to-end: 4–10 weeks from first sketch to permit (longer if a variance is needed), then one to three weeks of construction with staged inspections — typically excavation/footing, waterproofing and drainage before backfill, then framing and final.
Don't be tempted to skip it
An unpermitted foundation cut is the worst category of unpermitted work: it is visible from the street, impossible to hide from a buyer's inspection, and structurally consequential if the lintel is wrong. Municipalities can order the work uncovered or removed, and insurers take a hard line on undocumented structural changes — our guide to the questions every owner asks about permits covers what enforcement actually looks like.
Skip the paperwork
Describe your project in plain English and Permits2Go finds, fills and assembles the exact municipal forms you need — for Toronto, Mississauga and municipalities across Ontario.
This guide is general information, not legal or professional advice. Permit requirements, by-laws and fees change and vary by municipality — always confirm the current rules with your local building department before you design or build.