Most homeowners picture a door at the side of the house and some stairs going down, and assume that is roughly what gets built. What actually gets built is an excavation, a cut through a structural foundation wall, a formed concrete stairwell engineered to resist soil pressure, waterproofing, drainage, guards and handrails, a door assembly detailed to keep water out, and often a canopy or grate over the top. A separate basement entrance is a self-contained project with its own permit, engineering, and failure modes. Two questions come before any of that. They decide whether the project is viable at all.
One claim is repeated everywhere, including on contractor sites, and it is worth correcting. A separate exterior entrance is not universally mandatory for a legal secondary suite in Ontario. What the Building Code requires is a compliant means of egress from the suite. A separate exterior entrance is the most common and often the cleanest way to provide it, which is why it has become the default assumption. The Code does permit shared egress arrangements in defined circumstances, where the required fire separations and other conditions are met. Two caveats matter in practice:
Your designer should confirm which route your house and municipality require before you budget for excavation. Where a separate entrance is required or preferred, the below-grade stairwell is the usual answer in GTA semis and detached homes, because the existing basement access almost always runs through the kitchen, hallway, or mudroom.
This question ends more separate entrance projects than any technical issue, and most articles never mention it. A below-grade stairwell is a structure, and it is subject to the side yard setback in your zoning by-law. Many GTA semis have side yards of 0.9 to 1.2 metres. A compliant stairwell with a landing and a guard needs more than that under most by-laws. If your side yard will not accommodate it, you have three options: a minor variance through the Committee of Adjustment, a different location, or a different egress strategy. A minor variance typically costs $1,500 to $3,000 in application and drawing fees. It takes three to six months once you account for the notice period, the hearing, and the twenty-day appeal window.
| 💡 KEY POINT Check zoning in week one, not after you have paid for design. Confirm the side yard setback, corner lot provisions, whether an entrance is permitted in the front yard, maximum lot coverage, and whether the stairwell affects parking or landscaping ratios. |
| Alternative | When it works |
| A rear walk-out | Where the lot slopes. A grade-level or near-grade rear entrance is cheaper, drier, safer in winter, and more pleasant to use. If the grade is anywhere close, it is worth the study |
| Converting an existing side door | Some houses already have one. The work becomes a stairwell rebuild, not a new excavation |
| A front entrance under an existing porch | Occasionally possible, and sometimes the only place with room |
| A shared entry vestibule | A small fire-separated vestibule serving both units, where the Code and your municipality permit it. The cheapest option by a distance when it works |
The landscaping is removed and the stairwell footprint is excavated, typically five to eight feet below grade depending on the basement floor level. The excavation must not undermine the existing foundation or anything adjacent. Before anyone digs, locates must be obtained through Ontario One Call, which is legally required. Private locates for buried services on your own property, such as a gas line to a barbecue or an irrigation system, are your responsibility to arrange separately.
An opening is cut through the concrete or masonry for the door frame. The opening is marked on both faces of the wall and cut with a diamond saw or core drill. A lintel is installed above it to carry the wall load across the cut, and the edges are prepared for the frame. Structural engineering is required where the wall carries significant load, which on a foundation wall is usually the case. Budget for a detail sealed by a P.Eng.
The stairwell is formed and poured concrete, or concrete block, enclosing the stairs from grade to the door. It must:
The guard is the detail people forget until the inspection. An open hole in a side yard needs one.
The stairwell walls and floor, and the foundation wall around the new opening, all need waterproofing. An unwaterproofed below-grade stairwell is a bathtub with a door at the bottom, and the water will find the door frame and the foundation cut. Pay particular attention to the junction where the new stairwell meets the existing foundation wall. That cold joint is where most of these entrances leak.
Drainage is the component most often under-designed. A below-grade stairwell collects every drop of rain and snowmelt that lands in it, plus runoff from the surrounding grade. It needs:
The last point is the complication. Stormwater generally cannot be discharged into the sanitary sewer, and many GTA municipalities prohibit it outright. Depending on the property, the answer is a connection to a storm system, a daylight discharge where grade allows, or a dedicated pit with a pump. There is a further issue. A stairwell drain usually sits below the level of the municipal sewer, which makes it another potential path for sewer backup. Discuss backflow protection for the stairwell drain with your plumber, alongside the main backwater valve. Resolve the drainage strategy at design. It is the difference between a dry entrance and an annual flooding problem.
The surrounding soil has to be retained, either by the stairwell walls or by a separate retaining wall adequate for the height. The grade around the top of the stairwell should also slope away from the opening, so surface water is not directed into it in the first place.
The door is an exterior egress door, weather-stripped, with a lockset operable from both sides. Clear width is commonly specified at 860 mm, subject to your designer’s confirmation. The frame must be properly flashed and caulked at the foundation interface. A well-built stairwell with a badly detailed door head is still a leaking entrance.
An open stairwell in a GTA winter fills with snow, and meltwater refreezes on the treads. For a suite you are renting, that is a tenant safety issue and a liability exposure. The options, in rough order of cost:
Whichever you choose, decide during design. A canopy has setback and permit implications of its own.
Excavating within a metre or two of a shared foundation needs care, and often engineering. Where the excavation could affect the adjoining foundation, underpinning or shoring may be required, and that changes the budget category entirely. Give the neighbour notice as a matter of course. Excavation beside a party wall is where a good relationship is worth more than being technically within your rights. A neighbour told in advance is far less likely to call the city.
| 💰 TYPICAL GTA PRICING, excluding HST. These figures are in addition to the building permit fee, and separate from the rest of the legal suite scope, which runs $90,000 to $130,000 in standard conditions. |
| Scope | Cost |
| Basic below-grade stairwell: concrete, waterproofing, drainage, door | $12,000 to $18,000 |
| Mid-range: retaining walls, improved landscaping, better door assembly | $18,000 to $25,000 |
| Complex: deep excavation, difficult drainage, engineering, premium finishing | $25,000 to $40,000 |
| Minor variance application, if required | $1,500 to $3,000, plus 3 to 6 months |
| Underpinning or shoring, where required | Substantial, priced separately |
The largest cost drivers are excavation depth, whether the drainage has a straightforward discharge point, and whether the foundation cut requires engineering.
The entrance requires a building permit, either as part of the secondary suite application or on its own. The submission generally includes:
Drawings must be prepared by a designer holding a Building Code Identification Number, an architect, or an engineer. The stairwell is inspected at framing and again at final. The inspector looks at stair dimensions, the guard, waterproofing, drainage, and the door installation before the permit is closed. Do not backfill or finish over anything the inspector still needs to see.
Maple Leaf Quality Renos designs and builds below-grade separate entrances as part of legal basement suite projects across the GTA. We check zoning and egress strategy before design begins, manage the engineering and permit applications, and resolve the drainage route on paper, not on site. Contact us for a free site assessment.
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