ADU construction cost in the Greater Toronto Area: per-square-foot ranges by unit type, soft costs and servicing, and the site conditions that push a budget upward.
Key takeaways
- ADU construction cost in the GTA is decided by your lot far more than by the unit you picture. Two identical 600-square-foot suites on different lots are not the same project.
- The visible drivers before design starts are rear-yard access, servicing distance, soil and frost depth, electrical capacity at the panel, tree protection, and finished size and specification.
- Soft costs land before a shovel moves: survey, arborist report, design, structural engineering, and municipal charges of $5,500 to $14,000 depending on the city.
- The regional construction window is April to November, so a late-autumn permit usually means a spring start and a winter of carrying costs.
ADU construction cost in the GTA is decided by your lot far more than by the unit you picture. Two identical 600-square-foot suites, one on a wide suburban lot with a side drive and one on a narrow downtown lot with no laneway and protected trees, are not the same project and will not carry the same price.
ADU construction cost drivers you can see before design starts
- Access to the rear yard. Whether equipment and material can reach the build area, or everything is carried through a side yard, is often the single biggest swing.
- Servicing distance. How far water, sanitary and hydro must be trenched from the house or the street.
- Soil, grading and frost depth, which decide what the foundation has to be.
- Electrical capacity at the main panel - a second dwelling unit frequently forces a service upgrade.
- Tree protection, which can dictate the footprint and add arborist and hoarding costs.
- Finished size and specification of the unit.
The soft costs that arrive before construction
These land before a shovel moves and are worth budgeting separately:
- Survey of the existing lot
- Arborist report where protected trees are in play
- Design and the permit drawing set
- Structural engineering
- Municipal charges, which are published and knowable per municipality Toronto: $8,000-$14,000 in permit, development and plan-review fees. Mississauga: $6,500-$11,000 including Region of Peel charges. Brampton: $5,500-$10,000 with second-unit registration. The regional construction window is April-November, so a late-autumn permit usually means a spring start and a winter of carrying costs.
York Region development charges move the number most
| Municipality | Charges included in the band | Permit, development and plan review fees |
|---|---|---|
| Vaughan | York Region development charges | $9,000 to $16,000 |
| Markham | York Region charges | $9,000 to $15,000 |
| Richmond Hill | York Region charges | $9,000 to $15,000 |
| Aurora | York Region charges | $8,500 to $14,000 |
| Newmarket | York Region charges | $8,000 to $13,500 |
We do not publish a per-square-foot number, because a number that ignores your lot is marketing rather than a quote - and a low headline that excludes engineering, servicing and the electrical upgrade returns later as change orders. Our sequence is a paid feasibility and site review first, then a fixed-scope price for design, permit and construction. The figure you approve is the figure you build to.