Rules by State
/ Washington
Washington WA ADU Rules
Last updated: April 2025 · Reviewed by ADU Journal editorial team
ADU Friendliness Score
75
★ Favorable
Size & Dimensions
Max ADU Size (Detached)
1000 sq ft
Max ADU Size (Attached)
1000 sq ft
Min ADU Size
No state minimum
JADU Max Size
500 sq ft
Max Height (Detached)
24 ft
Stories Allowed
2 stories
Setbacks & Lot Coverage
Rear Setback
5 ft
Side Setback
5 ft
Front Setback
Same as primary dwelling
Minimum Lot Size
None
Fire Sprinklers
Not required if primary does not have them
Owner Occupancy & Rental Rules
Owner Occupancy Required?
No
Short-Term Rental (Airbnb)
Varies by city
Rental Income Allowed?
Yes
ADUs Per Lot
1 ADU + 1 JADU
No owner occupancy required
Permitting Process
Review Timeline (Ministerial)
60 days
Permit Fees
Reduced fees
Design Review Required?
No
Preapproved Plans Available?
Some cities