ADUs are allowed in BlaineTypes:DetachedInternal
Types:DetachedInternal
Accessory Dwelling Unit (ADU) Rules for Blaine, WA
Is your property eligible for an ADU?
# of Properties
3,392
Owner-occupied
51%
Zoning districts
38
Avg Home Value
$524,507
Median Lot Size
0.21 acres
Avg Income
$82,883
Residential Types:
3,392 housing units
Single Family
35%
2-3 Family
4%
Apts (4+ units)
4%
Condos
11%
Other
47%
Zoning Districts:
4,124 parcels · 38 districts
RPR
22%(894)
PR
15%(603)
RL
13%(550)
MPR
11%(448)
Other
40%(1,629)
ADU Rules
What can you build in Blaine, WA?
Blaine, WA follows state and local rules for Accessory Dwelling Units. Here is a concise overview of the local rules.
Eligibility
- –Internal / Attached ADU: By Right
- –Detached ADU: By Right
Interior / Attached ADU Size Limits
- –Maximum attached/internal ADU size based on the home’s floor area: under 2,000 sq ft—50%; 2,000–2,999—lesser of 40% or 1,000 sq ft; 3,000–4,999—lesser of 30% or 1,200 sq ft; 5,000+—lesser of 20% or 1,500 sq ft.
Detached ADU Size Limits
- –Maximum detached ADU size by lot area: 6,000–8,000 sq ft lots—the lesser of 50% of the primary residence or 600 sq ft; 8,001–11,000—the lesser of 50% or 800 sq ft; over 11,000—the lesser of 50% or 1,000 sq ft.
- –With a Conditional Use Permit, a detached ADU may be up to 1,000 sq ft.
Owner Occupancy
- –Owner-occupancy required; majority owner must occupy main or ADU as residence.
Parking
- –1 space per bedroom per ADU (citywide); in 17.43 district: 0.5 stall per studio and 1 stall per other unit; parking off alley where feasible; parking need not be in an enclosed building.
ADU State Law
What can you build in Washington?
- –ADUs are allowed by right, including attached, internal, and detached ADUs.
- –Local governments must allow up to two ADUs per lot.
- –Maximum ADU size is 1,000 sq ft for both attached and detached units.
- –ADU height is limited to 24 ft or the height of the principal dwelling, whichever is less.
- –Setbacks must use the less restrictive of accessory structure or principal dwelling standards.
- –Lot coverage and yard coverage rules may not be more restrictive than those applied to the principal home.
- –Parking requirements are capped, and parking cannot be required within ½ mile of major transit.
- –Owner occupancy may not be required for ADUs.
- –ADUs may be rented long-term or sold separately; local short-term rental rules may still apply.
- –Local governments may not regulate ADUs more restrictively than the principal unit. This includes setbacks, yard coverage, lot coverage, and height.
- –Cities and counties may be more permissive, but not more restrictive, than Washington's state ADU standards.
- –Some zoning rules still come from local code. Standards like FAR, bulk limits, and general lot coverage continue to apply as long as they do not prevent the lot from meeting the state-required ADU entitlements (e.g., allowing two ADUs with the required dimensions).
- –Washington's statewide ADU mandates apply only within Urban Growth Areas.
- –Outside UGAs, local zoning controls whether ADUs are allowed and under what conditions.
- –Additional constraints often apply outside UGAs, including septic capacity, fire access, water availability, and environmental regulations.
What's allowed on your lot?
These are the municipality-wide rules. What's allowed on a specific property also depends on state laws, setbacks, floor area ratio, lot coverage, environmental constraints, topography, and other property-specific factors. Search your address on FutureLot to see what's allowed on your property.
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ADU rules in other Washington municipalities
Rules change at the town line. Check the municipality your property is actually in.
Whatcom County