BuildRules/Ottawa/Secondary dwelling unit

Ottawa project guide

Do you need a permit for a secondary dwelling unit in Ottawa?

Understand Ottawa secondary dwelling unit permit triggers, including additions, enlarged windows, exterior doors, shared entrances and plumbing-only cases.

2 min readReviewed Oct 1, 2026

The short answerConditional

A building permit is required when the new unit includes specified construction such as an addition, enlarged window, new exterior door or new internal shared entrance; some basement-apartment cases may require only a plumbing permit.

Ottawa’s published guidance is deliberately scope-based. The permit route changes with the work, so define the proposed construction before assuming every secondary unit uses the same application.

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Know what matters

What changes the answer.

Start with these conditions. The official reference is attached to each one.

Specified constructionBuilding permit requiredConditional

Ottawa lists additions, enlarged windows, new exterior doors and new internal shared entrances as building-permit triggers for a new secondary dwelling unit.

Official sourceCity of OttawaSecondary dwelling unit/apartment FAQ · Permit triggers for secondary dwelling units

Verified2026-10-01Open proof

Some basement conversionsPlumbing permit may be the only permitConditional

Ottawa notes that in some basement-apartment cases only a plumbing permit may be required.

Official sourceCity of OttawaSecondary dwelling unit/apartment FAQ · Permit triggers for secondary dwelling units

Verified2026-10-01Open proof

ZoningReview the property before constructionInfo

The City recommends reviewing the proposed secondary dwelling unit with a Building Official before work starts.

Official sourceCity of OttawaSecondary dwelling unit/apartment FAQ · Permit triggers for secondary dwelling units

Verified2026-10-01Open proof

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Written scope of the unit conversion
Existing and proposed floor plans
Window, door and entrance changes
Plumbing information
Other plans required for the actual construction scope

Open the focused permit checklist

Fees and timing

TimelineConfirm the current municipal review stream after the application is accepted as complete.

FeesConfirm the current Ottawa fee schedule for the exact permit class.

Next steps

Define every construction change
Confirm whether the scope triggers a building permit, plumbing permit or both
Review the property and plan with the City
Submit the applicable permit package before construction

Same project, different city

See how this rule changes across Ontario.

Compare the source-reviewed answer for this project across every municipality BuildRules currently covers.

Compare secondary dwelling unit rules by city

Better decisions, together

Get everyone on the same page.

Send this to your designer or contractor before agreeing on the scope.

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Turn the published rules, documents, timing and questions to verify into one project-specific preparation brief.

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Research guidance only. Municipal approval and professional design are separate.

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Tell us what kind of help you need. We’ll save the request with your project and municipality so a relevant provider can respond if a match is available.

BuildRules principle

Do not confuse “no permit” with “no rules.”

Zoning, overlays, safety rules and other constraints can still apply.

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