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Serving Whitby & Durham Region
Modular Homes & Garden Suites in Whitby, Ontario
Factory-direct modular homes and backyard suites for Whitby and Durham Region. Here's what Whitby's additional-dwelling-unit by-law allows in your backyard, what it costs, and the rules that apply.
What you can build in Whitby
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 Whitby'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 Whitby 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? (Whitby lots typically allow up to ~750 sq ft)
Whitby allows a detached suite up to 75 m² (≈807 sq ft). Your exact lot may allow more or less — get the real number for your address in seconds.
Check your exact Whitby address →Can you put a garden suite (ADU) in your Whitby backyard?
Often, yes — Whitby permits a detached Additional Residential Unit on most serviced residential lots. The specifics, from Town of Whitby Zoning By-laws 1784 / 2585 / 5581-05 (ADU provisions):
| Max size | 75 m² (≈807 sq ft) for a detached suite |
|---|---|
| Max height | 4.5 m (≈15 ft) in residential zones; 5.5 m (≈18 ft) in other zones |
| Setbacks | 1.2 m (≈4 ft) rear and side |
| Units per lot | Up to 3 additional units — at most one detached |
| Parking | 1 space per ADU (tandem or a reduced 2.5 m × 5.0 m space allowed; none required in a Major Transit Station Area) |
| Servicing | Municipal water & sewer, or Durham Health-confirmed private servicing |
| Conservation | Central Lake Ontario (CLOCA); TRCA in the west |
Check your specific Whitby 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 Whitby, and the models that fit →
Whitby's by-law is verified in our checker, so you can check if a garden suite is allowed at your Whitby address in about a minute.
Getting your building permit in Whitby
An eligible lot still needs a building permit before anything is delivered. Here's how Whitby's process actually works — verified against the Whitby building department's own pages.
How do you apply for an ADU building permit in Whitby?
Through Town of Whitby E-Portal (application portal ↗). Apply through the Town's E-Portal (preferred), by email, or on paper in person — E-Portal submissions must follow the Town's file-naming convention and submission standards. Whitby's building-permit page ↗
- Start with a pre-application consultation with Building Services (building@whitby.ca) to confirm zoning compliance for the detached unit
- Determine what other approvals apply — minor variance, CLOCA permit, or Durham Region Health Department approval on septic lots
- Prepare the mandatory documents: the provincial Application to Construct or Demolish, Schedule 1 Designer Information, drawings per the Town's ADU Design Guide, and the Applicable Law Checklist
- Submit through the E-Portal following the file-naming and submission-standards guides
- The Town pre-screens for completeness, then issues an invoice — pay it and formal plan review begins
- Once the permit issues, schedule inspections during construction, plus a final exterior inspection before occupancy
- Register the ADU with By-Law Services (required under Registration By-law 8156-25)
What does an ADU permit application in Whitby need?
- Application to Construct or Demolish (the provincial form)
- Schedule 1: Designer Information form(s)
- Drawings meeting the Town's Additional Dwelling Unit Building-Specific Design Guide and the Building Code
- Applicable Law Checklist + Letter of Authorization if applying on the owner's behalf
- CLOCA permit where the lot is in a regulated area; Durham Region Health approval on private septic
- Certificate of Acceptance from a Licensed Electrical Contractor (during construction)
How much does an ADU building permit cost in Whitby?
Expect roughly $600 in Town permit fees for a typical ~600 sq ft (55 m²) detached ADU at the 2026 accessory-structure rate of $10.65 per m² (minimum fee $305) — an estimate; ask staff which fee code applies to a new-build detached ADU before quoting an exact figure. The bigger number: Whitby's ADU Incentive Agreement can reimburse the permit fee, registration inspection fee, curb-cut fee, and (for detached ADUs) Education Development Charges.
| Permit fee | $10.65 per m² for new residential accessory structures (2026 Schedule N, By-law 7220-17); minimum $305 |
|---|---|
| ADU registration | $268 (rises to $534 if the Town discovers an unregistered ADU via a complaint; $107 to transfer to a new owner) |
| ADU Incentive Agreement | Reimburses the permit fee, registration inspection fee, curb-cut fee, and Education Development Charges for detached ADUs — hard deadlines apply (see below) |
Whitby's DC by-law exempts ADUs that add no new floor area to an existing building; a new detached ADU isn't automatically exempt — but Education Development Charges on detached ADUs are reimbursable under the ADU Incentive Agreement.
How long does an ADU building permit take in Whitby?
Ontario's Building Code requires a decision on a complete house-class application within 10 business days. The Town recommends submitting at least two weeks before any incentive-program deadline to allow processing time.
Registration: All ADUs must be registered with By-Law Services under Registration By-law 8156-25 — $268, rising to $534 if an unregistered unit is discovered via a complaint.
Worth knowing before you apply
- The ADU Incentive Agreement has hard deadlines: the permit application must be complete by December 31, 2026, the signed agreement returned by March 31, 2027, and the ADU registered by March 31, 2027 — miss the registration date and the incentive must be repaid
- Whitby and Pickering jointly publish an ADU Regional Design Catalogue of five pre-approved detached designs (permit review then covers siting only) — round-1 submissions are closed and a second round was anticipated via HAF-ADU@whitby.ca; confirm current status
- A private-septic lot needs Durham Region Health Department approval before or alongside the permit — the common trip-up on Whitby's rural/estate lots
- Lots near a watercourse, wetland, or floodplain need a separate CLOCA permit on top of the building permit
- Breaking ground before the permit issues triggers a penalty fee under the 2026 fee schedule
Fees and timelines are estimates from Whitby'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 Whitby
Can I add a garden suite on a septic system in Whitby?
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 Whitby: The septic check has to be in writing (a septic capacity letter) before the building permit is issued.
Who approves septic systems in Whitby?
Durham Region Health Department, the local health unit, approves septic systems in Whitby, 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 Whitby
Town of Whitby — Additional Dwelling Unit (ADU) Incentive Program (open) — The Town reimburses the ADU building permit fee, registration inspection fee, curb-cut fee, below-grade-entrance fee and, for a detached ADU, education development charges. Complete building permit application by Dec 31, 2026; ADU registered by Mar 31, 2027. 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 →
Whitby modular homes — FAQ
Can you put a garden suite in Whitby?
Yes. Whitby permits up to three additional dwelling units per lot (with at most one detached) on urban residential land — subject to size, height, and setback rules and a building permit.
How big can a garden suite be in Whitby?
A detached suite can be up to 75 m² (≈807 sq ft). Check your address for the specifics.
Can you put a modular home in Whitby?
Yes. On land you own, a modular home on a permanent foundation is legal residential housing under the Ontario Building Code throughout Whitby, subject to standard zoning and permits.
How much does a modular home or backyard suite cost in Whitby?
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 Whitby?
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 Whitby Zoning By-laws 1784 / 2585 / 5581-05 (ADU provisions); verified by Modular Homes 400 and reviewed by James Clarke, REALTOR®. Always confirm current requirements with the municipality before you build.