For most of the last two decades, what you could build on a residential lot in Ottawa was decided by a zoning system that sorted land by building type. A lot zoned R1 was built for one detached house, and if you wanted more units on it, you generally needed a rezoning application, a committee process, and no guarantee of approval. On January 28, 2026, City Council voted unanimously to replace that entire system. The new by-law, 2026-50, was enacted March 11, 2026.

The headline rule is simple. Every serviced residential lot in Ottawa can now carry up to four dwelling units without a rezoning. Whether four units actually fit on your specific lot is a different question, and it depends on your zone, your frontage, your servicing, and a few other details this guide walks through.

Can You Actually Build a Fourplex on Your Property?

If your property was zoned R1 under the old system, it very likely falls into Ottawa’s new N1 zone today, the lowest-density category in the new Neighbourhood zoning framework. N1 permits up to four dwelling units as-of-right. That means no rezoning application, no Committee of Adjustment hearing, and no public meeting required, provided your design fits the existing rules for your zone.

That last part is the one people skip. As-of-right zoning sets the unit count. It does not remove the setback, height, and lot coverage rules that apply to your property, and it does not guarantee four units will physically fit on a narrow or oddly shaped lot. The City’s own announcement described the new by-law as the most housing-friendly in Ottawa’s history, and CBC News coverage of the council vote confirmed the new rules allow four units on every serviced residential lot and raise height limits to three storeys in nearly all residential areas.

What Ottawa’s New Zoning By-law Actually Changed

• Four units as-of-right, city-wide. Every serviced residential lot can now carry up to four dwelling units without a zoning amendment, one unit above the province-wide minimum set by Ontario’s Bill 23.
• Building-type zones replaced by size-based zones. The old R1 through R5 categories are gone. In their place, Neighbourhood zones N1 through N4 set the maximum units and height for a lot based on scale and location rather than what the building is called.
• Height limits raised. Three-storey height limits now apply in nearly all residential areas, including lower-density suburban neighbourhoods that were previously limited to bungalow-scale development.
• Parking minimums removed. Minimum parking requirements were eliminated city-wide, which matters most on smaller lots where a mandatory parking space could previously rule out an extra unit.
• Taller buildings near transit and major streets. Zones along busy streets and near major transit stations allow greater height, supporting the missing-middle housing types the by-law is aimed at.

Is Your Lot Fourplex-Ready?

As-of-right zoning is a starting point, not a guarantee. A handful of site conditions decide whether four units actually fit.

• Your specific N-zone. N1 sets a four-unit baseline, but N2, N3, and N4 allow more units and greater height depending on location. Confirm your zone before assuming a number.
• Lot frontage and depth. Four units may be permitted on paper while a narrow frontage or shallow lot limits what setbacks and lot coverage rules actually allow in practice.
• Servicing capacity. Water, sewer, and electrical connections sized for one household may need upgrades to support four units, and this is where budgets tend to move the most.
• Appeal status. Some provisions of the new by-law remain under appeal to the Ontario Land Tribunal. Where a provision is under appeal, the corresponding rule from the old by-law, 2008-250, continues to apply until that appeal is resolved.

A proper zoning review checks all of this against your specific address before any design work begins, which is the point where a fourplex either gets confirmed, scaled back, or ruled out for that lot.

What Still Requires a Building Permit

As-of-right zoning removes the political risk of a rezoning fight. It does not remove the technical requirements. Every project still needs to meet:

• The Ontario Building Code
• Setback requirements from your property lines
• Height limits for your specific N-zone
• Lot coverage maximums
• A full building permit application and review through the City

If a design cannot meet these rules within the standard envelope, a minor variance application through the Committee of Adjustment is still required, and that process typically adds several months to a project timeline.

What Determines Your Design and Construction Approach

Two lots with the same zoning can call for very different fourplex designs. Frontage, servicing condition, grade, and whether the existing structure can be adapted or needs to be replaced all shape what a compliant, buildable fourplex looks like on a given property. This is why a zoning permission and a finished design are two different things, and why a site-specific review matters more than a general rule of thumb.

Fourplex vs Secondary Suite vs Coach House

Design Work in Ottawa

25:8 Architecture + Urban Design’s Ottawa portfolio has been covered by Dezeen, which featured the studio’s Bird Wing Ottawa Residence, along with Dwell and ArchDaily. The pattern across that work carries directly into multi-unit design, working with a lot’s specific constraints, grade, frontage, and existing structure, rather than treating zoning permission as the whole design brief.

Frequently Asked Questions

Can I build a fourplex anywhere in Ottawa?

On most serviced residential lots, yes, as-of-right and without rezoning under By-law 2026-50. Whether four units physically fit depends on your specific N-zone, lot frontage, and servicing capacity.

Do I still need a building permit?

Yes. As-of-right zoning removes the need for a rezoning approval, but you still need a full building permit application that meets the Ontario Building Code and your zone’s setback, height, and lot coverage rules.

Is the new zoning by-law fully in effect?

By-law 2026-50 was enacted March 11, 2026, but some provisions remain under appeal to the Ontario Land Tribunal. Where a provision is under appeal, the previous by-law’s rule applies until that appeal is resolved.

Do I need parking for a fourplex?

No. Ottawa removed minimum parking requirements city-wide under the new by-law.

What’s the difference between a fourplex and a secondary suite or coach house?

A fourplex is four self-contained units within one building. A secondary suite is a second unit inside the existing house, most often a basement apartment. A coach house is a separate, detached unit in the rear yard. All three are permitted as-of-right, but they suit different lots and different goals.

Why Work With 25:8 on an Ottawa Fourplex

25:8 Architecture + Urban Design is led by Jay S. Lim, OAA, OAQ, AIA, RAIC, LEED AP, who has taught architectural design and building technology at Carleton University’s Azrieli School of Architecture and Urbanism for over a decade, alongside prior teaching and jury work at Columbia, Waterloo, and Ryerson. The studio’s work has been covered by Dezeen, Dwell, and ArchDaily, with further mentions in Ottawa Magazine and Steel Design Magazine.

A fourplex project succeeds or fails on the site-specific detail, frontage, servicing, grade, more than on the zoning headline. That is where the studio’s attention goes first, on every project regardless of scale.