ADUs are allowed in LyndenTypes:DetachedInternal
Types:DetachedInternal
Accessory Dwelling Unit (ADU) Rules for Lynden, WA
Is your property eligible for an ADU?
# of Properties
5,601
Owner-occupied
72%
Zoning districts
19
Avg Home Value
$571,787
Median Lot Size
0.22 acres
Avg Income
$102,616
Residential Types:
5,601 housing units
Single Family
45%
2-3 Family
2%
Apts (4+ units)
2%
Condos
16%
Other
34%
Zoning Districts:
6,376 parcels · 19 districts
RS-100
42%(2,661)
RS-72
14%(912)
RM-2
7%(449)
RM-3
6%(407)
Other
31%(1,947)
ADU Rules
What can you build in Lynden, WA?
Lynden, 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 size of 1,000 sq ft for an internal accessory dwelling unit (in-home apartment).
Detached ADU Size Limits
- –Maximum size for a detached accessory dwelling unit is 1,000 sq ft.
Max Units
- –Detached single-family: up to 2 ADUs per lot; may be attached or detached.
- –Duplex or other non-detached: 0 ADUs per lot.
- –Multifamily zones: up to 2 ADUs per lot where permitted.
Owner Occupancy
- –Owner must occupy either the primary residence or ADU until 2026.
Parking
- –1 space per ADU bedroom; lots ≥ 6,000 sq ft max 2 spaces for the ADU, lots < 6,000 sq ft max 1 space; ADU parking in addition to primary residence; all parking on-site.
Rental Restrictions
- –Short-term rentals in ADUs are allowed but limited: in residential zones require a home occupation permit, may host only one guest group at a time, and the operator must reside on the premises.
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