ADUs are allowed in ColfaxTypes:DetachedInternal
Types:DetachedInternal
Accessory Dwelling Unit (ADU) Rules for Colfax, WA
Is your property eligible for an ADU?
# of Parcels
2,085
Zoning districts
6
Zoning Districts:
2,015 parcels · 6 districts
R-1
67%(1,348)
R-2
15%(298)
B
14%(289)
C
2%(33)
Other
2%(47)
ADU Rules
What can you build in Colfax, WA?
Colfax, 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 800 sq ft when the primary dwelling’s living area is at least 1,000 sq ft
- –Maximum size of 40% of the primary dwelling’s living area when that living area is at least 1,000 sq ft
Detached ADU Size Limits
- –Maximum detached ADU size of 800 sq ft
- –Maximum detached ADU size is 40% of the primary dwelling’s living area; if the primary living area is under 1,000 sq ft, no detached ADU is allowed
- –A detached ADU’s total floor area is limited by a 10% lot coverage cap on its footprint multiplied by the number of ADU stories
Max Units
- –1 ADU per legal lot on a single-family lot
- –0 ADUs permitted on lots with two or more single-family residences
- –0 ADUs permitted on duplex or multifamily lots
Owner Occupancy
- –Owner must occupy one unit as principal residence.
Parking
- –1 off-street space per ADU; no reductions/waivers listed; driveway permit required per Chapter 12.08
Rental Restrictions
- –Simultaneous rental of both ADU units prohibited; one unit must be owner-occupied as the principal residence.
- –Owner-occupied unit may not be rented or occupied when the owner is absent for the remainder of the year.
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.
Whitman County