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 1,000 sq ft living area. Attached ADUs can be up to 1,000 sq ft living area. 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 1,000 sq ft living area. Attached ADUs are limited to 1,000 sq ft living area. Junior ADUs (JADUs) have a cap of N/A (Washington does not use a separate JADU category). Maximum height is 35 feet. You are allowed up to Up to 2 ADUs per lot on a qualifying lot.
Rear setback: 15 feet (no setback required from an alley). Side setback: 5 feet (8 feet if the main entrance faces the side property line). Front setback: Per underlying zone; Confirm with Tacoma Permits. Note that garage conversions may be exempt from setback requirements if the existing structure is already within the setback area.
Not required (per Washington HB 1337). 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. Plan check: 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/month, 2-bedroom units for $1,650-$2,300/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 No minimum — allowed on any legally established lot regardless of size or width. 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.