Complete 2026 cost breakdown: construction, permits, financing, and expected rental ROI.
Calculate your Tacoma ADU cost →Building an ADU in Tacoma costs between $150,000-$350,000 for new construction, with per-square-foot costs averaging $300-$520. These figures include design, permitting, site preparation, and construction. The most affordable option is a garage conversion at $75,000-$180,000, while prefab/modular ADUs fall in between at $170,000-$340,000.
| Cost Category | Estimated Range |
|---|---|
| Architectural Plans | $3,000 – $15,000 |
| Permits & Fees | PDS Fee Estimator (2026): building and site permit plus plan review about $2,000 for a 300 sq ft studio, $3,500 for 520 sq ft and $6,600 for 1,000 sq ft (valuation $170.80/sq ft x 1.31%, plus 45% plan review, site development and 17% surcharges). Electrical, water and sewer fees are separate. |
| Impact Fees | Transportation impact fee since June 1, 2026 (TMC 10.31, Ord. 29082): an ADU pays 50% of the single-family rate for its district; per-trip rates run $741 (Northeast Tacoma) to $5,201 (Southeast Tacoma) plus 3% admin, due before the permit issues, deferrable to final inspection. No school or park impact fees. TPU connection charges: power $970-$1,797; water $176 on the house meter, $5,922-$10,272 for a separate service. |
| Site Prep & Foundation | $10,000 – $35,000 |
| Framing & Structure | $15,000 – $45,000 |
| Plumbing | $8,000 – $20,000 |
| Electrical | $5,000 – $15,000 |
| HVAC | $3,000 – $8,000 |
| Interior Finishes | $15,000 – $40,000 |
Quotes for the same ADU commonly vary 20–40% between builders. We pass your request to up to 5 local builders serving Tacoma, where we have them — free, no obligation.
Get Tacoma builder quotes →Permit fees in Tacoma are PDS Fee Estimator (2026): building and site permit plus plan review about $2,000 for a 300 sq ft studio, $3,500 for 520 sq ft and $6,600 for 1,000 sq ft (valuation $170.80/sq ft x 1.31%, plus 45% plan review, site development and 17% surcharges). Electrical, water and sewer fees are separate.. The review timeline is PDS publishes no fixed ADU review target; its Permit Timeline page reports actual first-review and issuance times for buildings of up to six units (Oct 2025-Mar 2026 snapshot). A 2026 industry guide budgets 3-5 months of review; pre-approved plans are quicker but still get a site-specific review., with plan check: Plans must show a site plan, floor plans, elevations, structural details, WSEC energy credits and fire separation; the ADU needs a separate visible address, its own heating and water-heater control, cooking, sanitation and sleeping facilities, and interconnected smoke/CO alarms if attached. Use the PDS Submittal Checklist for a Detached or Attached ADU.. Impact fees are Transportation impact fee since June 1, 2026 (TMC 10.31, Ord. 29082): an ADU pays 50% of the single-family rate for its district; per-trip rates run $741 (Northeast Tacoma) to $5,201 (Southeast Tacoma) plus 3% admin, due before the permit issues, deferrable to final inspection. No school or park impact fees. TPU connection charges: power $970-$1,797; water $176 on the house meter, $5,922-$10,272 for a separate service.. Pre-approved plans: Yes. Four City pre-approved DADU base models: Unit A 300 sq ft studio; Unit B 520 sq ft one-bedroom; Unit C 845 sq ft two-bedroom over a 647 sq ft garage; Unit D stacked duplex of two 534 sq ft one-bedrooms (counts as two ADUs). Each comes in two roof styles with siding options and meets Home In Tacoma standards. The plan sets, site evaluation and staff site visit are free; permit fees and a site-specific review still apply..
| 1-Bedroom Rent | $1,450-$2,050/month |
| 2-Bedroom Rent | $1,780-$2,500/month |
| Annual Rental Income (est.) | $21,000/year |
| Payback Period (est.) | 11.9 years |
| Short-Term Rental | Allowed for the ADU or the main house only if the owner occupies one of the two dwellings (TMC 13.06.080.A.4.g); renting individual guest rooms requires the owner to be home during the stay (TMC 13.06.080.M). |
| Overall ROI Estimate | 6-9% gross yield (e.g. $1,700/mo on a $250,000 build is about 8% before vacancy, taxes and the impact fee) |
A typical ADU in Tacoma generates approximately $21,000 per year in rental income based on average 1-bedroom rents. At an average construction cost of $250,000, the estimated payback period is 11.9 years — before accounting for the resale value the ADU adds, which an appraiser determines from comparable sales in Tacoma and varies by market (often less than build cost).
1. Garage conversions save 40-60% vs new construction since the shell already exists. Average cost in Tacoma: $75,000-$180,000.
2. Prefab/modular ADUs offer predictable pricing and faster timelines. Average: $170,000-$340,000.
3. Pre-approved plans — available in Tacoma, which can save $3,000-$10,000 in design costs and 2-3 months in review time. See which cities offer pre-approved ADU plans.
4. State grants — California's CalHFA ADU grant (up to $40K) is currently paused; check calhfa.ca.gov/adu for status and your state for active programs.
5. Get multiple bids — ADU contractor pricing varies 20-40% for the same project. We recommend getting at least 3 quotes.
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