BuildRules/London/Additional residential unit

London project guide

What do you need for an additional residential unit in London, Ontario?

Check London additional residential unit requirements for building permits, zoning, drawings and the published 15-business-day review period.

1 min readReviewed Oct 1, 2026

The short answerConditional

A building permit is required for every new ARU, whether it is an interior/basement conversion, converted garage, addition or detached unit.

London treats ARUs as a dedicated permit path with zoning review, site planning and construction drawings.

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What changes the answer.

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

ARU permitBuilding permit requiredConditional

London states that an approved building permit is required before construction of any new ARU.

Official sourceCity of LondonAdditional Residential Units · ARU types, permits, zoning and review period

Verified2026-10-01Open proof

ARU typesInterior, garage, addition or detachedInfo

London identifies four main ARU types: interior/basement conversion, converted garage, detached and addition to an existing building.

Official sourceCity of LondonAdditional Residential Units · ARU types, permits, zoning and review period

Verified2026-10-01Open proof

ZoningReviewed as part of the processInfo

The City states that zoning compliance is reviewed through the building permit process.

Official sourceCity of LondonAdditional Residential Units · ARU types, permits, zoning and review period

Verified2026-10-01Open proof

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Permit to Construct or Demolish
Schedule 1 / designer information as applicable
Site plan or survey
Existing and proposed construction drawings
Mechanical/servicing information

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Fees and timing

TimelineLondon publishes a 15-business-day review period for secondary dwelling units in houses once the application is complete.

FeesConfirm the current London permit fee for the exact project class before filing.

Next steps

Choose the ARU type
Confirm zoning and site feasibility
Prepare the complete drawing package
Submit before construction

Same project, different city

See how this rule changes across Ontario.

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BuildRules principle

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

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

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