Accessory dwelling unit plans that pass review in Ontario: one- and two-bedroom layouts, footprint and height limits, setbacks, and stock versus custom drawings.
Key takeaways
- Accessory dwelling unit plans come in two forms, and only one gets a building permit: a concept plan is a layout, a permit set is a stamped, property-specific drawing package.
- A stock plan is drawn without a lot. Your lot is the constraint, and separation distance, angular planes, tree protection, emergency access, coverage caps and servicing routes all reshape it.
- Mississauga's 2022 ARU by-law caps an accessory-structure unit at 10% rear-yard coverage, and by-law rules differ from municipality to municipality across the GTA.
- We design from your survey outward: the feasibility review establishes the buildable envelope first, then the layout is drawn inside it.
Accessory dwelling unit plans come in two forms, and confusing them costs homeowners months. A concept plan is a layout - the sort you download or sketch. A permit set is a stamped, property-specific drawing package that a municipality will actually review: site plan against your survey, floor plans, elevations, sections, structural engineering, servicing and Code compliance details. Only the second one gets you a building permit.
Why stock accessory dwelling unit plans rarely survive a GTA lot
A stock plan is drawn without a lot. Your lot is the constraint. In the GTA the plan has to be reshaped around:
- Separation distance from the main dwelling and the rear/side setbacks
- Height and angular-plane limits that cut into upper-floor area
- Tree protection - a protected tree can move the entire footprint
- Emergency access from the street on lots with no laneway
- Coverage caps - Mississauga's 2022 ARU by-law limits an accessory-structure unit to 10% rear-yard coverage
- Servicing routes - where water, sanitary and hydro can physically be trenched
Any one of these can invalidate a purchased plan, and by-law rules differ from municipality to municipality across the region.
How we produce ADU plans that get permitted
We start from your survey, not from a catalogue. The feasibility review establishes the buildable envelope first; the design is then drawn inside it, so the layout you approve is a layout the municipality can issue on. From there we produce the full permit set - stamped structural, servicing, Code details - submit it, and carry the review comments through to permit issuance.
Concept plan or permit set
| Concept plan | Permit set | |
|---|---|---|
| Drawn against | A generic lot | Your survey |
| Contents | Layout only | Site plan, floor plans, elevations, sections, structural engineering, servicing and Code compliance details |
| Stamped by a professional | No | Yes |
| Municipality will review it | No | Yes |
| Gets you a building permit | No | Yes |
If you already own plans you like, bring them. We will tell you honestly which parts survive your lot's envelope and what has to change, before you spend anything on construction. The review is written down, so you can take it to a lender, a designer or a second builder without depending on our word for it.