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.
Quick quiz: test what you learned
Three questions, all answered in this guide. Click an answer to check it.
1. When does a new below-grade entrance need a building permit in Ontario?
Every below-grade entrance cuts into the foundation, and the small-structure exemption has no equivalent here.
2. Why does cutting a new door opening into a basement wall require an engineer?
The foundation is a structural wall — the new opening needs an engineered lintel or beam sized for the loads above.
3. What is a realistic end-to-end timeline from first sketch to permit for a below-grade entrance?
4 to 10 weeks is realistic for a complete application — longer if a minor variance is needed.
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.