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Garage Conversions in Ajax, Ontario: design, permit and build on a single contract. A typical 700 sq ft unit estimates at $114,000-$168,500 (about $388/sq ft), with $7,000-$12,000 including Durham Region charges in municipal approvals and a April-November construction season.

Converting an existing detached or attached garage into heated, insulated living space or a fully self-contained coach house unit.
Service area
Ajax, Ontario
Durham Region
Typical build estimate
$114,000-$168,500
about $388/sq ft in Ajax
Municipal approvals
$7,000-$12,000 including Durham Region charges
quoted separately from the build
Build season
April-November
121 cm snow · -3.8°C winter avg
Frost depth
1.2 m
footing depth, OBC Part 9
Local market
126,666
residents · walkability 47/100
Ajax subdivisions from the 1990s were built with side yards as narrow as 1.2 m, which is the real limiter on what ADU type we can bring to the back of the property. On a Nottingham or Applecroft lot the choice between panelised and stick-built is decided by a tape measure at the side gate, not by budget. Ajax permits additional dwelling units town-wide under the provincial three-unit framework, with Durham Region reviewing water and sanitary capacity.
Compact 1990s-2000s subdivision lots where the required 1.2 m side-yard construction access sets the maximum module width we can crane in. Ajax sees 121 cm of snow and -3.8°C winter averages.
A garage was never built to be lived in: the slab sits above frost, the walls are usually uninsulated single-wythe, and the header over the vehicle door carries nothing. Every Ajax conversion therefore starts with a structural and thermal assessment of what is already standing. The slab is the decisive item - an existing garage slab rarely bears on a 1.2 m footing, so we either underpin the perimeter or pour a new insulated slab inside the existing walls before any framing begins.
Converting the garage removes a parking space, which is why the 47/100 walkability of Ajax matters more on this form than on any other - it decides whether parking relief is arguable or the driveway has to absorb the loss.
Everything you need to know about our services.
A typical 700 sq ft build in Ajax estimates at $114,000-$168,500 - about $388/sq ft, set by $7,000-$12,000 including Durham Region charges in approvals, a 1.2 m frost-depth footing requirement and 121 cm of annual snow load. Final pricing follows the site visit.
Related service: Our ADU services
Ajax permits additional dwelling units town-wide under the provincial three-unit framework, with Durham Region reviewing water and sanitary capacity. Approval costs in Ajax run $7,000-$12,000 including Durham Region charges, quoted separately from construction so the permit stage holds no surprises.
Related service: Our ADU services
Compact 1990s-2000s subdivision lots where the required 1.2 m side-yard construction access sets the maximum module width we can crane in. At 47/100 walkability, Ajax suites usually keep one parking space: enough to clear the zoning review without surrendering the whole yard. We work regularly in Pickering Village, Westney Heights, Discovery Bay.
Related service: ADU Building Permit
Rarely as-is. Most Ajax garage slabs are shallow, uninsulated and poured above the 1.2 m frost line, so they fail both the structural and the thermal requirement for habitable space. We either underpin the perimeter or pour a new insulated slab inside the standing walls - that decision is made at the first site visit and it is the single largest cost variable on this form.
Related service: Our ADU services
Get a free, no-obligation quote from GTA ADU Builders - zoning review, permit drawings and construction for ADUs across the GTA.