Scenario 1
Keep the house and add 2 units
Keep the existing house, add a basement or in-house suite and a garden suite.
- Added floor area65–135 m² (700–1,453 sq ft)
- Units2–3 units incl. the house
- Approval pathAs of right (zoning review and building permit)
- Timeline3–6 months approvals + 6–12 months construction
How we estimated it
- Additional units
- up to 2Property report: second units and garden suites screen
- Second unit
- 65 m²Second unit (basement or in-house) about 65 m² (typical, needs confirmation)
- Garden suite
- 70 m²Garden suite about 70 m² (check the municipal by-law) (typical, needs confirmation)
- Timeline
- approvals 3–6 months, construction 6–12 monthsApproval and construction months (typical, needs confirmation)
Key risks
- Screen: Zoning is not in open data here: the screen assumes a house lot (detached, semi-detached or townhouse)
- Screen: Partly or wholly in a conservation authority regulated area: units are not permitted in a floodplain or on hazard lands; a CA permit may be needed
- In a TRCA regulated area: a permit is needed before building.
- Garden and laneway suites need fire access from the street and room for servicing; check both early.
Rough budget and residual land value
Enter your own figure. We could not verify the Altus Group 2026 Canadian Cost Guide ranges (free download at altusgroup.com/featured-insights/canadian-cost-guide); use its range for this building type in your market, or a builder's quote.
Your own estimate of what the finished space sells (or is worth) per sq ft. This public tool does not use MLS® sales data.
Design, permits, consultants, legal, insurance and marketing: commonly 15–25% of hard cost (typical, needs confirmation).
Second and third units are exempt. Rates: Development Charges Act, 1997 s. 2(3) to (3.3): second and third units in or beside a house are exempt · York Region development charges, By-law 2026-20, effective May 21, 2026, full water and wastewater (single/semi $84,718; multiple $72,392; apartment 700 sq ft or more $58,721) · Education development charge in York Region (public and Catholic boards), $8,934 per dwelling (combined guide effective July 1, 2026) The local municipality's own development charge is not in our table yet: add it to the per-unit figure.
Construction loan rate (typical, needs confirmation).
On average about half the cost is drawn over the build (typical).
Builder's margin on revenue: commonly 12–20% (typical, needs confirmation).
Share of gross floor area that is sellable or rentable (walls, stairs and halls excluded).
Enter a hard cost and a sale value per sq ft to see the value added.