City of London’s New ADU Rules Coming Into Effect November 2025
1. City Review of ADU Policies Begins November 2025
London has confirmed that its ARU policies are entering a formal review period beginning November 2025. This review will influence how ARUs are permitted and regulated going forward.
This matters for homeowners considering an ADU build, because the current limitations remain in force until the review results in updated zoning.
2. Interim Control By-law Rules Still Apply (For Now)
Until new regulations replace them, the Interim Control By-law (CP-1600-300) continues to govern ADU design and bedroom limits.
Key restrictions include:
ADU Size Restrictions
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An ADU cannot exceed 80% of the gross floor area of the main home.
Maximum Number of Units Allowed
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Up to three ARUs are permitted on a lot, for a total of four units including the primary dwelling — where zoning allows.
Bedroom Limits (Temporary but Important)
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Each ADU/ARU may have up to 2 bedrooms.
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A maximum of 3 bedrooms is allowed among units inside or attached to the main home.
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Another 3 bedrooms total are allowed among detached ADUs.
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Across all additional units combined, the maximum allowed is 5 bedrooms.
These rules are especially important for investors planning multi-unit conversions or backyard homes.
3. Detached ADU Placement & Lot Rules
If you’re planning a detached backyard ADU, these restrictions remain in effect through November 2025:
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Detached ADUs must follow accessory building regulations.
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They are only permitted in the rear yard or interior side yard—never the front yard.
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They must comply with lot coverage, landscaping, and open-space requirements.
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No new driveway can be created solely to serve an ADU.
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No additional parking is required for ARUs.
These placement rules play a major role in determining whether a backyard suite is feasible on your lot.
4. ADUs Continue to Be Allowed “As-of-Right”
If your ADU design meets the November-2025 rules, you can proceed through the standard building permit process without needing rezoning or variances.
This “as-of-right” status remains one of London’s strongest incentives for homeowners looking to add rental units, multigenerational housing, or a mortgage-helper suite.
Why These ADU Changes Matter for London Homeowners
The November 2025 ADU rules support London’s goals of increasing housing supply, encouraging gentle density, and giving property owners more flexibility. The interim restrictions ensure ADUs remain modest in size while the city finalizes long-term guidelines.
For homeowners and investors, this means:
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Clearer expectations during the 2025–2026 transition period
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Continued ability to create income-generating rental units
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Increased future property value potential
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Opportunity to get ahead of zoning changes that may expand or adjust ADU permissions
Thinking About Building an ADU in London?
With London’s ADU rules evolving, now is the ideal time to explore your property’s potential!