Everything homeowners ask about building an ADU in Tacoma — answered with 2026 data.
Yes, ADUs are allowed in Residential zones (most) in Tacoma, WA. The maximum size for a detached ADU is 1,100 sq ft. Attached ADUs can be up to 900 sq ft. Tacoma has an ADU-friendliness score of 8/10. Check our full Tacoma ADU rules page for complete zoning details.
ADU construction in Tacoma typically costs $135,000-$270,000. The cost per square foot averages $125-$245. Garage conversions are more affordable at $65,000-$155,000, while prefab ADUs cost $100,000-$230,000. Permit fees add $1,800-$2,800 to your budget. See our detailed Tacoma ADU cost guide.
Detached ADUs in Tacoma can be up to 1,100 sq ft. Attached ADUs are limited to 900 sq ft. Junior ADUs (JADUs) have a cap of 750 sq ft. Maximum height is 35 feet. You are allowed up to 1 ADU per lot on a qualifying lot.
Rear setback: 10 feet. Side setback: 3 feet. Front setback: 15 feet. Note that garage conversions may be exempt from setback requirements if the existing structure is already within the setback area.
Optional. Many cities and states have been relaxing ADU parking requirements in recent years. In California, no additional parking is required for ADUs near transit.
Not required. Note that owner-occupancy rules vary by state law — California and several other states have eliminated this requirement for standard ADUs.
The ADU permit review timeline in Tacoma is typically 40-60 days. The plan check process takes approximately 2-3 weeks. Pre-approved plans availability: Available for common types.
Average ADU rental income in Tacoma: 1-bedroom units rent for $1,300-$1,750/mo/month, 2-bedroom units for $1,650-$2,300/mo/month. Short-term rentals: Restricted to primary residence owners. Expected ROI: 7-9% annual return.
The minimum lot size for an ADU in Tacoma is 3,500 sq ft. This applies to detached ADUs — garage conversions and JADUs may have different or no lot size requirements.
Garage conversions are one of the most popular and affordable ADU options. In Tacoma, a garage conversion typically costs $65,000-$155,000. The key advantages are lower cost (no foundation work), potential setback exemptions, and faster permitting. Read our complete garage conversion guide.