Building Types | Fourplex
Building a Fourplex in Ottawa
A fourplex is four dwelling units in one building. It is the workhorse of Ottawa missing middle housing, because four units are permitted as-of-right on a serviced residential lot under By-law 2026-50 — one unit above Ontario's Bill 23 floor.
Why the Fourplex Is the Default
It uses the full Ottawa allowance
Four units is the as-of-right ceiling in the base N1 zone. A fourplex captures the maximum the zoning hands you without a rezoning.
It spreads fixed costs over more units
Servicing, the lot, and the approval work are largely the same at three or four units. A fourth unit shares those costs across more revenue.
It stays as-of-right where the lot fits
No rezoning, and no minor variance if you meet the size envelope. Your risk is whether it fits, not whether the City allows it.
The fourth unit rides on costs you already pay for the first three. That is the core reason the fourplex is the default. The catch is fit: four units still has to land inside the zone's size envelope. When it does not, a triplex is the next step down.
Three Common Fourplex Layouts
Two front, two rear
Two units face the street, two face the rear yard, each with its own grade entrance. This reads like a pair of homes from the front and keeps four separate doors.
Fully stacked
Four units over the building's floors, often two up and two down, sharing a stair. Best on narrower lots where you build up rather than spread across the lot.
Two-and-two split
A side-by-side pair at the front, each with a second unit stacked above or behind. A middle path when the lot is neither very wide nor very narrow.
The two-front, two-rear layout is the one most people picture: four separate grade entrances, two facing the street and two facing the back. On a narrow lot you stack instead. Lot width, depth, and the zone's height limit decide which layout actually fits.
Four Units, and No Forced Parking
By-law 2026-50 removed minimum parking requirements city-wide (City of Ottawa). For a fourplex that matters: a parking minimum was often the thing that stopped four units from fitting a standard lot. Without it, more of the lot can go to the building. You can still provide parking where it makes sense. The base N1 zone allows up to four units; in higher N-zones the count rises further. Confirm your zone and standards on geoOttawa, then test the numbers with the feasibility check.
Best For
- ✓ Serviced lots wide and deep enough to fit four units to the zone standards.
- ✓ Owners and builders who want the maximum as-of-right unit count without a rezoning.
- ✓ Projects where the fixed costs are set and a fourth unit improves the return.
Usually Fails When
- ✕ The lot caps out at three units to the size envelope — a triplex fits, a fourplex needs a variance.
- ✕ Your lot is on septic or only partially serviced, which limits units before the zoning does.
- ✕ Frontage is too narrow for four grade entrances and a stacked form does not suit the design.
What To Verify Before Spending Money
- → Your lot is fully serviced with municipal water and sewer.
- → Your Neighbourhood zone and its lot-area, frontage, height, and coverage standards on geoOttawa.
- → Whether the four-unit layout you want fits the size envelope without a minor variance.
Frequently Asked Questions
Can I build a fourplex in Ottawa as-of-right?
Why is the fourplex the default Ottawa missing middle form?
What are common fourplex layouts in Ottawa?
Do I need parking for a fourplex in Ottawa?
Official Sources Referenced
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