Built from Desire Basements' completed GTA suites, the 2024 Ontario Building Code and the City of Mississauga's own rules. Every figure is sourced at the bottom of the page.
Every municipality applies the same Ontario Building Code and Fire Code, but the approval path differs from one city hall to the next. This is Mississauga's.
| Item | The Mississauga rule |
|---|---|
| Where a suite is allowed | A second unit is a self-contained living space within a detached house, semi-detached house or townhouse, and it must meet the Ontario Building Code, the Ontario Fire Code and the Zoning By-law. |
| Permit | A building permit with sign-off from every City inspector: framing, insulation, plumbing, HVAC, electrical (ESA) and final. |
| Registration | Mandatory, and free. Once the permit is closed you complete the Second Unit Registration Form and email it with proof of ownership and a copy of the permit to secondunits@mississauga.ca. The City keeps a public Second Units Registry, updated monthly. |
| Enforcement | Unregistered units can be reported to 311 and inspected. Registration is what turns a finished basement into a rentable unit. |
| Fees | No registration fee; the building permit and inspections are the City's charges, and they are inside every Desire quote. |
We prepare the drawings, file the permit with the City of Mississauga, book every inspection and, where the City requires it, complete the registration. Nothing in that list lands on your desk.
These are the items the inspector checks, and the ones a cheap quote quietly leaves out. They come from the 2024 Ontario Building Code provisions for a secondary suite in an existing house.
| Requirement | Minimum | What it means on site |
|---|---|---|
| Ceiling height | 1.95 m (6 ft 5 in) | 1.85 m allowed under beams and ducts. Lower than that means underpinning or bench footing before anything else. |
| Egress window | 0.35 m² clear opening | No dimension under 380 mm; it must open without tools and stay open on its own. |
| Fire separation | 30 minutes | Between the suite and the rest of the house, floor assembly and shared walls, doors included. |
| Smoke alarms | Interconnected | Every smoke alarm in the house sounds together, hard-wired or wireless, so a fire in one unit wakes the other. |
| Carbon monoxide alarms | Each bedroom and storey | Beside every sleeping room in the suite and on each storey, where the house has fuel-burning appliances. |
| Doors | 810 mm suite entrance | Bedroom doors at least 760 mm. Old 24-inch basement doors do not pass. |
| Separate entrance | Required | A walkout or side entrance, or a properly separated shared entry; a walkout runs $15,000 to $25,000 all in. |
The suite is priced like any other basement, then the Code items are added as lines you can see. Our published finish rates are $55, $70 and $90 per square foot; a suite is usually built at Essential or Signature, because the tenant pays for a warm, quiet, well-lit unit, not for stone.
| Line item | Typical cost |
|---|---|
| Finished space, 800 to 1,000 sq ft at Essential or Signature | $44,000–$70,000 |
| Three-piece bathroom with tiled shower | $18,000–$28,000 |
| Walkout or separate entrance, permits included | $15,000–$25,000 |
| Kitchen, fire separation, alarms, egress window, permit and inspections | included in the suite quote |
| Full-perimeter underpinning, only where the ceiling is under 1.95 m | $60,000–$120,000 |
| Typical purpose-built legal suite, no underpinning | $75,000–$110,000+ |
Desire Basements published rates and itemized add-ons; every project is quoted exactly after a free in-home consultation. Full breakdown in the 2026 GTA cost report.
Mississauga's post-1970 houses in Meadowvale, Erin Mills, Streetsville and Malton mostly carry full-height basements, and many already have a side entrance, so the suite budget goes into the kitchen, the bathroom and the fire separation rather than into excavation. Our Mississauga median completed project is $76,000 across all basement types, the lowest of the cities we publish, which reflects simpler builds rather than lower rates.
GTA legal suites rent for $1,700 to $2,400 a month in 2026. Move the sliders to your build cost and the rent you expect, and the calculator shows gross payback and ten-year income. It is a planning tool, not a quote and not tax advice.
Gross figures before property tax, insurance, utilities, maintenance and income tax. Rent range from the Desire Basements 2026 cost report. Financing can spread the build into monthly payments the rent typically covers.
Design first: a free in-home visit, measurements, a ceiling-height check and a free 3D design of the suite. Then permit drawings, filed with the City of Mississauga while the design is finalised, so review time overlaps with planning instead of following it. Construction takes about eight weeks for a typical basement; suites run to the longer end of our 4 to 11 week range because of the kitchen, the second bathroom and the fire-separation work, and underpinning adds weeks of its own. Every quote is fixed and itemized before you sign, the timeline is written into the contract and backed by our $200-per-day on-time guarantee, and the workmanship carries a lifetime warranty.
Purpose-built legal suites in Desire Basements projects typically land between $75,000 and $110,000 or more, with underpinning ($60,000 to $120,000 full perimeter) extra where the ceiling is under the 1.95 metre minimum. The finished space, bathroom, separate entrance, kitchen, fire separation, alarms, egress window, permit and inspections are all inside that number.
Yes. A building permit from the City of Mississauga with staged inspections, and the suite must meet the 2024 Ontario Building Code and the Ontario Fire Code. Desire Basements prepares the drawings, files the permit and manages every inspection.
GTA legal suites rent for $1,700 to $2,400 a month in 2026. At $2,000 a month, a $95,000 suite pays back its gross cost in a little over four years, before operating costs and tax.
1.95 metres (about 6 feet 5 inches) under the 2024 Ontario Building Code for a secondary suite in an existing house, with 1.85 metres allowed under beams and ducts. Below that, underpinning or bench footing is required first.
Yes. A walkout or side entrance, or a properly fire-separated shared entry. A new walkout entrance costs $15,000 to $25,000 all in, permits included.
Sources: City of Mississauga additional residential unit and second unit rules as published by the City; Ontario Building Code 2024, Part 11, secondary suites in existing houses; Desire Basements completed-project data, 2026 GTA Basement Cost Report. See also the Mississauga basement renovations and the rental income guide. Municipal rules change; confirm the current requirement with the City before you sign a lease.
