Jarvis / Design & build
Guides to Building and Renovating in Ontario
Guides for Durham and GTA homeowners on what building and renovating cost, which permits apply, additional residential units, and how design-build works.
The homeowner’s notebook
Good decisions
start here.
Design-build or architect plus contractor in Ontario?
Design-build or an architect plus a general contractor for an Ontario addition: who carries the risk, who files the permit, and why the 10% holdback applies.
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Do you need a permit to finish a basement in Durham Region?
Yes. Every Durham Region town needs a permit to finish a basement: about $356 to $693 for 700 sq ft at 2026 rates, plus a $1,000 deposit in Pickering.
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Fixed price vs cost-plus contracts for Ontario renovations
Fixed price or cost-plus for an Ontario renovation or addition: how each prices risk, the 10% estimate rule, deposits, holdbacks and what to put in writing.
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HCRA licence and Tarion warranty: who needs them in Ontario
New Ontario homes need an HCRA-licensed builder and Tarion's warranty, up to $400,000. Renovations and additions don't. Here's where the line falls.
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How many units can I add to my lot in Ontario?
Bill 23 lets you have three units on most serviced Ontario lots, and Whitby, Ajax and parts of the GTA allow four. Compare Durham Region and GTA town rules.
Read the guideHow much does a home addition cost in Ontario in 2026?
We price home additions at $350 to $600 a sq ft in 2026, and a 300 to 700 sq ft rear addition at $180,000 to $450,000. Durham permit fees, worked out.
Read the guideHow much does a second-storey addition cost in Ontario in 2026?
Our 2026 range for a 600 to 1,200 sq ft second storey is $300,000 to $800,000 before HST. What quotes leave out, plus Durham Region permit fees by town.
Read the guideIs it cheaper to build up or out? 2026 Ontario costs
Our 2026 ranges: $300,000 to $800,000 to build up a storey, $180,000 to $450,000 for a rear addition. Your lot decides: Durham height and coverage limits.
Read the guideOntario HST relief for owner-built homes and big renovations, 2026
Ontario's 2026 to 2027 HST relief can return up to $130,000 on an owner-built home or substantial renovation started by 31 March 2027. Here's the test.
Read the guideQuestions to ask a contractor in Ontario before you sign
Questions to ask an Ontario renovation contractor before you sign: permits, WSIB clearance, insurance, licences, a 10% deposit cap, holdbacks and cooling-off.
Read the guideShould we add on or move? Costs compared for 2026
Moving to a $1,200,000 home in Durham costs $20,475 in land transfer tax, and $40,950 in Toronto, before commission. How that stacks up against an addition.
Read the guideWhat does a legal basement apartment cost in Ontario in 2026?
We price a legal basement apartment at $80,000 to $180,000 in 2026, or $45,000 to $95,000 to legalise a finished one, plus Durham fees and a tax credit.
Read the guideWhat does a legal basement apartment need in Ontario?
A legal basement apartment in Ontario needs 1.95 m ceilings, a fire separation, egress windows and linked smoke alarms, plus your Durham town's zoning rules.
Read the guideWhitby's ADU incentive: fees refunded for applications by 31 Dec 2026
Whitby refunds additional dwelling unit permit fees for complete applications by 31 December 2026. The rules: 75 m², 4.5 m, $268 to register, the designs.
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