Home/Modular Homes by City/Ajax
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) |
Check your specific Ajax address →
Garden suite, laneway suite, in-law suite, ARU, ADU — different names for the same thing: a small, self-contained home in the backyard. New to the idea? Start with prefab garden suites for Ontario — what one costs in Ajax, and the models that fit →
Ajax's by-law is verified in our checker, so you can check if a garden suite is allowed at your Ajax address in about a minute.
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 an ADU permit application in Ajax 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.
A garden suite on a well and septic in Ajax
Can I add a garden suite on a septic system in Ajax?
Yes, if your septic system can carry the house and the suite together. A garden suite with a kitchen and bathroom adds a new source of sewage, so a qualified septic designer checks the combined load before you order. If the system has room, the suite can connect to it; if not, it may need to be altered, expanded or replaced.
In Ajax: The septic check has to be in writing (a septic capacity letter) before the building permit is issued.
Who approves septic systems in Ajax?
Durham Region Health Department, the local health unit, approves septic systems in Ajax, so the septic review is a separate desk from the building permit.
Durham Region Health Department: septic permits ↗ · 905-668-2020 · buildingapplications@durham.ca
What to gather, and why even a small suite needs the check: our guide to garden suites on a septic system →
From Durham Region Health Department’s own page, checked October 24, 2026. Confirm with them before you apply.
Grants & financing in Ajax
Town of Ajax — Build More, Get More Grant Program for ADUs (closed) — A cash-back grant per new dwelling unit ($2,000 for one, $3,000 each for two, $4,000 each for three), paid after the permit is closed. Closed to new applications; ask about a further round. Details →
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 garden 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 garden 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 municipality before you build.