Max Your Lot: Fourplex + Garden Suite Explained
- Henry Matthew Silva Rojas
- Jul 9
- 1 min read
Fourplex + Garden Suite: Can You Build 5 Units on 1 Lot?
Double the units, double the fun? Combining a fourplex with a garden suite (detached ADU) can skyrocket your rental yield, but it also creates a regulatory puzzle.
Zoning Limit
Ontario now generally permits up to 4 units per lot,
But most cities still cap it there.
Adding a 5th unit (like a laneway or garden suite behind a fourplex) usually exceeds the density limit.
You’ll likely need a zoning variance or even an official plan amendment — so don’t skip that check.
TRIPLE CHECK before proceeding or running your numbers!
Lot Coverage & Size
A garden suite has strict size caps:
Fire Code limit: Maximum 75 m² (800sqft) or 90% of the main floor, whichever is smaller (applies to 2–3 bedroom units)
City bylaws add more rules: Local rules may further restrict lot coverage, especially when stacking multiple units. Sometimes unfinished basements count as floor area, thus causing issues with the MAX area requirement.
Backyard room is tight: Double-check yard setbacks and total building coverage before finalizing your design
🔌 Separate Systems
Think of the garden suite as its mini-house:
Dedicated setup: Must have its address, kitchen, HVAC, and parking space
Fire safety first requires fire separation from the main home (especially if above grade)
Plumbing alert: If you’re planning a basement laundry or kitchen, don’t forget a backwater valve.
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