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Serving Ajax & Durham Region
Modular Homes & Garden Suites in Ajax, Ontario
Factory-direct modular homes and backyard suites for Ajax and Durham Region. Here's what Ajax's accessory-dwelling-unit by-law allows in your backyard, what it costs, and the rules that apply — plus a Town grant.
What you can build in Ajax
Full modular homes — from $175,696. 29 models from 560 to 1,405 sq ft, 1–3 bedrooms — factory-built to the Ontario Building Code and set on a permanent foundation (a real, permanent house, not a “trailer”).
Backyard suites (ADUs) — from $96,244. 7 compact models built for garden-suite and in-law-suite use, sized to fit what Ajax's by-law allows.
All homes are CSA-certified (A277 modular / Z240MH manufactured), finished in the factory, and delivered ready for foundation and hook-up. What's the difference between modular, manufactured, and mobile? →
Find your backyard suite — 3 quick questions
We'll narrow the models that fit a typical Ajax backyard allowance to the ones that fit your life. No email needed.
1 · Who's it for?
2 · What layout?
3 · What size feels right? (Ajax lots typically allow up to 646 sq ft)
The numbers above use Ajax's typical allowance. Your exact lot may allow more or less — get the real number for your address in seconds.
Check your exact Ajax address →Can you put a garden suite (ADU) in your Ajax backyard?
Often, yes — Ajax permits a detached Additional Residential Unit on most serviced residential lots. The specifics, from Town of Ajax Zoning By-law 95-2003 §4.4 (added by By-law 23-2025):
| Max size | 60 m² (≈646 sq ft) ground-floor area — and must be smaller than your main house’s ground floor |
|---|---|
| Max height | 4.5 m (≈15 ft) one-storey; up to 6.1 m (≈20 ft) for a suite above a detached garage |
| Setbacks | 0.6 m (≈2 ft) rear and interior side; 3.0 m (≈10 ft) separation from the main house |
| Units per lot | Up to 3 ADUs (4 dwellings total) — at most one detached |
| Parking | None required for the first ADU |
| Servicing | Municipal services or a Durham Health-approved septic |
| Conservation | Central Lake Ontario Conservation Authority (CLOCA) |
Getting your building permit in Ajax
An eligible lot still needs a building permit before anything is delivered. Here's how Ajax's process actually works — verified against the Ajax building department's own pages.
How do you apply for an ADU building permit in Ajax?
Through Town of Ajax Online Application Portal (application portal ↗). Residential permit applications — including detached ADUs — are submitted through the Online Application Portal at eapply.ajax.ca; drawings upload there and review happens electronically. Ajax's building-permit page ↗
- Check your lot on the Town's ADU Property Mapping Tool (housing.ajax.ca/mappingtool) first — it shows zoning, setbacks, buildable area, and max height for a detached unit
- Prepare the package: site plan or survey, construction drawings (BCIN designer or engineer where required), and supporting forms
- Submit the application and documents through the Online Application Portal
- Town staff pre-screen for completeness, then email you the exact permit fee and payment instructions
- Pay the fee through the portal; plans examiners review for Building Code and zoning compliance
- The permit issues — print the permit card and one full to-scale set of approved plans for the inspector's use on site
What does a Ajax ADU permit application need?
- Completed building-permit application form
- Legal survey or site plan showing all structures, dimensions to lot lines, and lot coverage
- Construction drawings of the detached unit (foundation, framing, elevations, cross-sections), stamped where required
- Schedule 1: Designer Information
- Proof of servicing — municipal connection details, or Durham Region Health Department septic approval on private services
- Parking plan where an additional space is required (third and fourth units)
How much does an ADU building permit cost in Ajax?
Ajax doesn't publish a flat permit rate — the Town emails the exact fee (set under Building Permit Fee By-law 48-2023) after its completeness pre-screen, so budget from that quote rather than an estimate; the Build More, Get More grant then offsets $2,000–$4,000 per unit after the permit closes.
| Permit fee | Set under Building Permit Fee By-law 48-2023; the Town emails the exact amount after the completeness pre-screen |
|---|---|
| Build More, Get More grant | $2,000 for 1 unit · $3,000/unit for 2 (max $6,000) · $4,000/unit for 3 (max $12,000) — paid after the permit closes; permits applied for Jul 2, 2025 – Mar 1, 2027 only |
An additional dwelling unit on a lot with an existing house of up to two units is exempt from development charges under the Development Charges Act; Ajax's DC By-law 13-2025 follows that provincial exemption framework.
How long does an ADU building permit take in Ajax?
Ontario's Building Code requires a decision on a complete house-class application within 10 business days. Ajax publishes the 10-business-day review standard — the clock effectively starts once the application passes the completeness pre-screen.
Worth knowing before you apply
- Run the ADU Property Mapping Tool check before designing — not every lot qualifies for a detached (vs. attached-only) unit
- The Build More, Get More grant pays AFTER the permit is closed (construction complete + final inspection) — don't rely on it for up-front financing, and note its Jul 2, 2025 – Mar 1, 2027 application window
- No parking is required for the first ADU, but the third and fourth units on a property each need an additional space
- On lots without full municipal services, Durham Region Health Department septic capacity approval is the common source of delay
- You only learn the exact permit fee after submitting a complete drawing package — budget accordingly
Fees and timelines are estimates from Ajax's published schedules, verified July 4, 2026. Rates and processes change — always confirm current requirements with the building department before you apply.
Grants & financing in Ajax
Build More, Get More — Town of Ajax grant — roughly $2,000–$4,000 per unit (up to $12,000). Confirm current intake.
See every program → Ontario ADU Grants Directory
A modular or prefab home on a permanent foundation is financed like any house. CMHC Prefab Plus allows an insured mortgage with as little as 5% down on the first $500,000, with construction funds released in stages. How modular home financing works →
Thinking of the suite as a rental? Run the numbers →
Ajax modular homes — FAQ
Can you put a backyard suite in Ajax?
Yes. Ajax permits up to three accessory dwelling units per lot (four dwellings total), with at most one detached — subject to size, height, and setback rules and a building permit.
How big can a backyard suite be in Ajax?
A detached suite can be up to 60 m² (≈646 sq ft) of ground-floor area, and must be smaller than your main house’s ground floor. Check your address for the specifics.
Can you put a modular home in Ajax?
Yes. On land you own, a modular home on a permanent foundation is legal residential housing under the Ontario Building Code throughout Ajax, subject to standard zoning and permits.
How much does a modular home or backyard suite cost in Ajax?
Modular home models start at $175,696 and run to about $338,000 for the largest layouts; backyard ADU models start at $96,244. Site work, foundation, delivery, and permits are additional.
Can I get a mortgage on a modular home in Ajax?
Yes — on a permanent foundation it is financed as real property, including via CMHC Prefab Plus (5% down on the first $500,000).
Local rules summarized from Town of Ajax Zoning By-law 95-2003 §4.4 (added by By-law 23-2025); verified by Modular Homes 400 and reviewed by James Clarke, REALTOR®. Always confirm current requirements with the City of Ajax before you build.