Pick a unit type, size, and finish level for an instant range.
Choose the project type, scope, and finish level. Your estimate updates instantly as you refine the details.
1. Select ADU Type
2. Unit Size
3. Finish Level
4. Add-ons
Every lot is different. This is a starting point, not a final recommendation – a feasibility check confirms what your property qualifies for.
Detached garden suite design, permits, and construction for Ottawa backyards. Also called a granny flat or backyard suite.
Coach house design, permits, and construction in Ottawa – a detached second dwelling unit built above or beside a garage or parking area.
Laneway suite design, permits, and construction for Ottawa properties with rear lane access – a detached unit with its own street presence.
Legal basement apartment, secondary suite, and in-law suite conversions in Ottawa – egress, fire separation, and permits handled.
These are the same ranges used in the calculator above.
$90-$220/sq ft
Uses existing foundation
Fastest to build
Lowest cost per sq ft
$260-$480/sq ft
Fully detached
New foundation required
Most design flexibility
$270-$490/sq ft
Fully detached
Requires registered lane access
Independent entrance
$250-$460/sq ft
Detached, above or beside parking
Structural upgrade to garage often required
Smaller lot footprint
A detached unit needs its own foundation, roof, and exterior envelope built from scratch, while a basement conversion reuses a foundation and structure that already exist. The detached unit's total project cost isn't necessarily higher for a given budget, but the cost per square foot usually is.
Yes, one federal option applies as of 2026. Since January 2025, federal mortgage insurance rules allow insured refinancing to fund a new secondary unit, up to 90 percent of the property's as-improved value on homes valued under $2 million, provided the homeowner or a close relative lives in one of the units. The Canada Secondary Suite Loan Program announced in 2024 never opened for applications. Program details change, so confirm current terms with your lender or a mortgage broker before finalizing a budget.
Not by default – toggle the design and permit drawing add-on in the calculator to include it. Committee of Adjustment costs are a separate add-on and only apply if your lot needs a minor variance.
Land value, ongoing property tax changes, and financing costs are not part of the estimator, since they depend on your specific mortgage, lender, and municipal assessment rather than on construction scope. If your project needs a Committee of Adjustment minor variance, that has its own line item in the add-ons – it is a separate cost from construction because it's a City Hall application process, not a build cost.
Site access, servicing, and finish level are usually the biggest factors within a single ADU type. Site access – whether equipment can reach the build location without demolishing a fence or removing a mature tree – affects both direct cost and schedule. Servicing – whether the unit can tie into existing water, sewer, and electrical infrastructure nearby or needs a longer run – is a bigger factor for detached units than for basement conversions, which usually share the main house's services. Finish level – stock fixtures and flooring versus upgraded cabinetry, tile, and trim – is the most controllable variable, which is why the calculator lets you toggle it directly.
Every project we build starts with a written quote based on an actual site visit and confirmed scope, not the calculator's range. Any workmanship warranty on the completed unit is set out in that quote, job by job – we don't offer a blanket guarantee independent of what's actually agreed to in writing.