Additional Dwelling Unit (ADU)
As a leading custom home builder and general contractor across the Greater Toronto Area (GTA) and the Kitchener-Waterloo-Cambridge region, Harji Custom Homes specializes in end-to-end Additional Dwelling Unit (ADU) construction. Whether you are building a legal basement suite for rental income, a detached garden suite for multi-generational living, or a custom 2-bedroom accessory apartment, we manage every detail from architectural design and municipal building permits to complete construction.
Harji Custom Homes
Model ADU Options
We offer 3 customizable, pre-designed ADU floor plans built for fast municipal permitting in the GTA and Waterloo Region. Minor layout tweaks, window placements, and door locations can easily be adjusted to fit your property.
Studio Model
Starting at $130,000 + HST
400 square feet
Studio apartment with Kitchen, 1 bath
Electric Split Heat Pump for heating/cooling
Our smallest and most economical model option
1 Bedroom Model
2 Bedroom Model
Starting at $155,000 + HST
600 square feet
1 Bedroom , 1 Kitchen, 1 Bath
Gas furnace & Electric AC (Lennox , HRV
Starting at $175,000 + HST
800 square feet
2 Bedrooms , 1 Kitchen, 1 Bath
Gas furnace & Electric AC ( Lennox ), HRV
Our most popular model and best value
*Please reach out for more information on layouts and costs of the above models. Prices mentioned above are for Build Cost only.
Frequently asked questions
What Is an ADU?
An ADU, or Additional Dwelling Unit, is a secondary housing unit on a residential property. In Ontario, these include basement apartments, garden suites, and tiny homes, providing flexible living options.
How Can You Get Started With Your ADU Project?
The first step is understanding what your property allows — local zoning, lot coverage, and setback rules vary by municipality across the GTA and Waterloo Region, and they shape everything from unit size to placement. From there, we handle the rest as your single point of contact: an initial consultation to assess your property and goals, selection from one of our three pre-designed models (or a custom layout), architectural drawings, and the municipal building permit application. Once permits are approved, our team moves straight into construction and project management through completion. Reach out and we'll walk your specific property through this process with you.
How much does it cost?
Pricing depends on the model and finishes you choose. Our three pre-designed ADU options start at $130,000 + HST — build cost only, before site-specific factors like excavation, utility hookups, or municipal fees. Custom layout changes can adjust these numbers. Reach out and we'll put together a cost breakdown for your specific property.
Do you offer Custom ADU's ?
Yes, we're a custom home builder at our core, so if your property or vision calls for something outside those layouts — different square footage, room configuration, or exterior finishes — we'll design and permit a fully custom ADU for you. Reach out with what you have in mind and we'll scope it out.
Is my property eligible for an ADU or garden suite?
Most residential lots across Ontario are now eligible for a second or third dwelling unit as-of-right under provincial policy, but eligibility on your specific property still comes down to local zoning: lot size and coverage, setbacks from property lines, height limits, parking, and servicing capacity (water, sewer, hydro) all vary by municipality — and rules in Toronto differ from Mississauga, Kitchener, or Cambridge. The only way to know for certain is a site-specific review. We do this as part of our initial consultation, at no cost to you, and tell you plainly whether your property qualifies before you spend anything on design.
How long does the ADU building takes, including permitting process, build start to finish?
Most straightforward projects run 6 to 8 months total: a few weeks for design, 6–14 weeks for permitting (longer if a zoning variance is needed), then approx 4 months of construction. Our pre-designed models are built for the faster end of that range. Basement conversions are quicker, typically 3–5 months.
Is building an ADU still a good investment given current construction costs?
This depends on your numbers, not ours — rental rates in your specific neighborhood, your construction cost, and how you're financing it all factor in. What we can tell you: build costs have risen across the industry, so it's worth pricing your specific project rather than going off outdated online estimates, and rental income potential varies a lot by unit size and location within the GTA/Waterloo Region. We're happy to walk through the cost side with you so you can weigh it against what you'd expect to earn or gain in property value — that's a decision worth making with real numbers for your property.
What's the difference between a garden suite, laneway house, and basement apartment?
A basement apartment is a secondary unit built within your existing home's foundation. A garden suite is a detached structure built in your backyard, separate from the main house. A laneway house is a specific type of detached suite built along a rear laneway with vehicle access — common in older Toronto neighborhoods but not relevant everywhere in the GTA/Waterloo Region. All three are regulated differently depending on your municipality, which is part of why we start every project with a property-specific review.
Do I need a separate architect, or does my builder handle design too?
You don't need to hire your own architect. We manage design in-house as part of our end-to-end process — from initial floor plan through the architectural drawings needed for your permit application — so you have one point of contact instead of coordinating between a separate designer and builder.
Harji Custom Homes transformed our vision into a stunning reality with flawless craftsmanship.
Maya & Tom
★★★★★
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