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ADU Construction in King, Ontario: design, permit and build on a single contract. A typical 700 sq ft unit estimates at $269,500-$361,000 (about $385/sq ft), with $9,000-$16,500 including York Region and septic charges in municipal approvals and a May-October construction season.

The construction phase itself - excavation, foundation, framing, services and finishes - for homeowners who already hold approved ADU drawings and a permit.
Service area
King, Ontario
York Region
Typical build estimate
$269,500-$361,000
about $385/sq ft in King
Municipal approvals
$9,000-$16,500 including York Region and septic charges
quoted separately from the build
Build season
May-October
150 cm snow · -5.3°C winter avg
Frost depth
1.2 m
footing depth, OBC Part 9
Local market
27,333
residents · walkability 21/100
King Township is almost entirely Oak Ridges Moraine and Greenbelt, with core-area designations that prohibit new building envelopes outright on some parcels. We run a moraine designation check against the property roll number before quoting a King City or Nobleton laneway-suite or garden-suite project, because on a core-area lot the honest answer is sometimes no. King Township permits additional dwelling units, with Oak Ridges Moraine and Greenbelt policies plus private servicing governing the majority of properties.
Estate and agricultural parcels, many over an acre, on private well and septic with moraine core-area restrictions. North-GTA snowfall of 150 cm and -5.3°C winters give King a May-October working season - foundations for adu construction go in before the ground closes, with interior finishing carried through the cold months.
Construction in King is sequenced around one hard date - the day the ground closes - because footings to 1.2 m cannot be poured into frozen soil without heat and hoarding costs that change the budget. Excavation, foundation and envelope land inside the May-October window; mechanical, drywall and finishing then run through winter, with inspections booked against York Region's calendar rather than ours. Roof structure on every King build is sized for 150 cm of annual snow load against -5.3°C design winters - the two numbers that separate a GTA build spec from a generic one.
Everything you need to know about our services.
A typical 700 sq ft build in King estimates at $269,500-$361,000 - about $385/sq ft, set by $9,000-$16,500 including York Region and septic charges in approvals, a 1.2 m frost-depth footing requirement and 150 cm of annual snow load. Final pricing follows the site visit.
Related service: Accessory Dwelling Units
King Township permits additional dwelling units, with Oak Ridges Moraine and Greenbelt policies plus private servicing governing the majority of properties. Approval costs in King run $9,000-$16,500 including York Region and septic charges, quoted separately from construction so the permit stage holds no surprises.
Related service: Accessory Dwelling Units
Estate and agricultural parcels, many over an acre, on private well and septic with moraine core-area restrictions. King is car-oriented at 21/100 walkability, so parking retention and driveway access constrain the footprint more than the zoning envelope does. We work regularly in King City, Nobleton, Schomberg.
Related service: Accessory Dwelling Units
The build is gated by the May-October season rather than by labour: the foundation has to be in before the ground closes, after which envelope and interior work continue through winter. Starting the permit early enough to pour in season is the single largest schedule lever on a King project.
Related service: Accessory Dwelling Units
Get a free, no-obligation quote from GTA ADU Builders - zoning review, permit drawings and construction for ADUs across the GTA.