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Detached ADU in Brock, Ontario: design, permit and build on a single contract. A typical 700 sq ft unit estimates at $268,000-$359,500 (about $383/sq ft), with $7,000-$13,000 including Durham Region and septic charges in municipal approvals and a May-October construction season.

Free-standing backyard dwellings that are neither laneway nor garden-suite specific - a detached unit sized to whatever the lot and by-law allow.
Service area
Brock, Ontario
Durham Region
Typical build estimate
$268,000-$359,500
about $383/sq ft in Brock
Municipal approvals
$7,000-$13,000 including Durham Region and septic charges
quoted separately from the build
Build season
May-October
167 cm snow · -6°C winter avg
Frost depth
1.2 m
footing depth, OBC Part 9
Local market
12,038
residents · walkability 18/100
Brock is the smallest and most rural municipality in the GTA - Beaverton, Cannington and Sunderland together hold barely twelve thousand people. Trade availability, not permitting, is the constraint here: we schedule Brock ADU builds in continuous blocks so crews are not driving ninety minutes each way for a half-day of work. Brock Township permits additional dwelling units; nearly all rural properties depend on private well and septic, with LSRCA review on Lake Simcoe frontage.
Agricultural parcels and Lake Simcoe shoreline lots, with the smallest population and lowest density of any GTA municipality. Brock takes the heaviest snowfall in the GTA at 167 cm a year with winters averaging -6°C, so detached adu here is engineered to a higher roof snow load and scheduled around a May-October window that closes early.
A detached unit stands clear of the main house, so it carries its own foundation, its own service laterals and its own exit - the three cost centres that separate it from an interior conversion on the same Brock lot. We trench services across the yard and pour to 1.2 m before the ground closes; framing, envelope and interior finishing then run through the cold months without holding up occupancy. Detached is the highest per-square-foot form of the four, and also the only one that leaves the existing house untouched - no shared walls, no disruption to the occupants during construction.
Everything you need to know about our services.
A typical 700 sq ft build in Brock estimates at $268,000-$359,500 - about $383/sq ft, set by $7,000-$13,000 including Durham Region and septic charges in approvals, a 1.2 m frost-depth footing requirement and 167 cm of annual snow load. Final pricing follows the site visit.
Related service: Accessory Dwelling Units
Brock Township permits additional dwelling units; nearly all rural properties depend on private well and septic, with LSRCA review on Lake Simcoe frontage. Approval costs in Brock run $7,000-$13,000 including Durham Region and septic charges, quoted separately from construction so the permit stage holds no surprises.
Related service: Accessory Dwelling Units
Agricultural parcels and Lake Simcoe shoreline lots, with the smallest population and lowest density of any GTA municipality. Brock is car-oriented at 18/100 walkability, so parking retention and driveway access constrain the footprint more than the zoning envelope does. We work regularly in Beaverton, Cannington, Sunderland.
Related service: Accessory Dwelling Units
A detached unit in Brock commands a higher rent and appraises closer to a standalone dwelling, because it has no shared entry and no shared mechanical. It also costs more per square foot: it needs a 1.2 m foundation and a roof engineered for 167 cm of snow that a basement conversion does not.
Related service: Basement Suites
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