Bellingham ADU Rules: A Homeowner’s Guide to Compliance
Key Bellingham ADU Regulations
Size Limits:
- Attached ADUs: Maximum 1,000 sq ft or 60% of the primary home’s square footage (whichever is smaller).
- Detached ADUs (DADUs): Up to 1,000 sq ft, with a maximum height of 24 feet (increased from 20 ft in 2023).
- Basement ADUs: No size limits if part of the existing home’s footprint.
Setbacks:
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Rear and Side Yards: 5 feet from property lines.
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Primary Dwelling: 10 feet separation for detached units.
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Exceptions: Non-conforming lots (common in older neighborhoods like York) may qualify for variances.
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Parking:
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Exemptions: No parking required if your property is within 0.5 miles of a high-frequency transit corridor (e.g., Bus Route 190, 331).
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Standard Requirement: 1 space per ADU outside transit zones.
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Owner Occupancy:
- Current Rule: Homeowners must occupy either the primary residence or ADU until July 1, 2026.
- Post-2026: Both units can be rented independently.
Challenges & Our Solutions
2023 Updates Impacting Your ADU
- Short-Term Rentals: Permitted in ADUs with a city-issued business license and safety inspection.
- Tree Retention: Reduced fees for removing trees under 12 inches in diameter on lots smaller than 5,000 sq ft.
- Design Flexibility: Exterior materials no longer need to “match” the primary home but must be “compatible” in style and quality.
Restricted Areas
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Lake Whatcom Watershed: ADUs require enhanced stormwater systems (e.g., permeable pavers, rain gardens) to protect water quality.
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Historic Districts: Fairhaven and South Hill ADUs must undergo design review for compliance with neighborhood aesthetics.
Common Compliance Mistakes
- Utility Missteps: Failing to upgrade sewer laterals in older neighborhoods (e.g., Alabama Hill) can lead to permit denials.
- Unpermitted Conversions: Converting a garage or basement without permits risks fines up to $5,000 + mandatory demolition.
- Short-Term Rentals: Renting your ADU on Airbnb without a business license can trigger penalties of $500/day.
How We Help You Stay Compliant
Free Zoning Report: Share your address, and we’ll provide a customized analysis of your lot’s ADU potential.
Design Review: Our architects ensure your plans meet Bellingham’s “cottage character” guidelines.
Permit Guarantee: If your permit is denied due to our oversight, we cover revision fees.
Get help with your ADU project
Make sure you stay in compliance every step of the way during the ADU building process. Contact our team today.