Yes. Tacoma allows two ADUs on any legally established residential lot, attached, detached or both, under TMC 13.06.080.A as rewritten by Home In Tacoma Phase 2 (Ord. 28986, effective Feb 1, 2025). Each ADU is capped at 1,000 sq ft of habitable area (garage and non-living space excluded); a detached ADU is a 'Backyard Building' with 5-ft side and 15-ft rear setbacks in UR-1/UR-2 (10 ft rear in UR-3, 0 ft at an alley) under a 35-ft zone height that drops to 25 ft in the rear 25 ft of the lot. No parking, no minimum lot size and no owner-occupancy except for short-term rentals. You need a residential new-construction building permit (PDS estimator: about $2,000 for a 300 sq ft studio to $6,600 for 1,000 sq ft), Tacoma Power and Water connection charges, and, since June 1, 2026, a transportation impact fee set at half the single-family rate.
In Tacoma you will also hear an ADU called a DADU — short for detached accessory dwelling unit, the usual term across Washington. The rules on this page apply either way.
Zoning & Size Requirements [1][2][3][4][5][6]
Yes — Tacoma allows ADUs. A detached ADU can typically be up to 1,000 sq ft under current Washington and Tacoma zoning rules.
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| Allowed Zones | All residential districts (UR-1, UR-2, UR-3, R-4, R-5) and the mixed-use center (X) districts where dwellings are permitted; TMC 13.06.080.A applies citywide as a subordinate use to any new or existing residential development. In the UR districts a detached ADU is regulated as a 'Backyard Building' housing type (TMC 13.06.100.F.4.b). |
| Max Size (Detached) | 1,000 sq ft of habitable area, excluding garage and other non-living areas (TMC 13.06.080.A.5.b). A Backyard Building is also limited to 40 ft wide (75 ft in UR-3) and 40 ft deep, and the lot's total floor area must stay within the UR FAR cap (UR-1: 0.6 for 1-2 units, 0.8 for 3+; UR-2: 0.8/1.0; UR-3: 1.0/1.2; TMC 13.06.020.F.1). |
| Max Size (Attached) | 1,000 sq ft of habitable area, excluding garage and non-living areas (TMC 13.06.080.A.5.b). An attached ADU follows the setbacks and height of the housing type it sits in (houseplex, rowhouse, etc.) and the same FAR cap for the lot. |
| Max Size (JADU) | N/A. Washington and Tacoma have no junior ADU category; a small unit inside the house is simply an attached ADU under the same 1,000 sq ft cap. |
| Max Height | No ADU-specific limit (TMC 13.06.080.A.5.c); the zone and housing-type limits control. UR-1/UR-2: 35 ft, but 25 ft within the rear 25 ft of the lot (35 ft there if a 12-in DBH tree is retained or under the owner-occupant ADU incentive); non-dwelling accessory buildings 15 ft. UR-3: 35 ft. Max 3 stories. In a View Sensitive overlay a backyard building with ADUs may not exceed the main house (TMC 13.06.020.F.1, F.3, F.5). |
| Max Units | Two ADUs per lot in any mix: two attached, two detached, or one of each (TMC 13.06.080.A.4.a; RCW 36.70A.681(1)(c)). A two-unit backyard building (the City's pre-approved Unit D duplex) counts as both. Separate ownership of units is allowed through a unit-lot subdivision (TMC 13.06.020.F.1; 13.04.093) or condominium (RCW 36.70A.681(1)(j)). |
Setback Requirements [1][2][3][4][5][6]
Tacoma requires a rear setback of about 15 ft for a detached ADU, and no additional parking is required. Owner-occupancy is not required — you can rent it out without living on the property.
| Rear Setback | 15 ft in UR-1/UR-2, 10 ft in UR-3; 0 ft from an alley, and the rear setback may be measured from the alley centerline (TMC 13.06.020.F.1; 13.06.100.F.4.b). Retaining a 12-in DBH tree cuts it to 10 ft (UR-1/2) or 7.5 ft (UR-3). Buildings on the same lot must be 6 ft apart, 10 ft if either is over 25 ft tall. |
| Side Setback | 5 ft, or 8 ft on any side of the building where a unit's primary entrance faces that side yard; 0 ft from an alley. A new backyard building behind an existing house may keep 5 ft where existing conditions prevent 8 ft (TMC 13.06.020.F.1). |
| Front Setback | 15 ft in UR-1/UR-2, 10 ft in UR-3 (TMC 13.06.020.F.1). A detached ADU is a Backyard Building and sits behind the street-facing structure; on a corner lot it may orient to the secondary street. R-4/R-5 lots use the TMC 13.06.020.G table. |
| Parking Required | None required (TMC 13.06.080.A.4.d; 13.06.090.C Table 1 footnote 17); existing off-street spaces may be removed to site the ADU. Any parking you add must be in the rear portion of the lot, accessed from the alley if one is developable, and never between the building and the street. State floor: RCW 36.70A.681(2). |
| Owner Occupancy | Not required to build or rent an ADU long-term (RCW 36.70A.681(1)(b); no requirement in TMC 13.06.080.A). One exception: to use the ADU or the main house as a short-term rental, the owner must occupy one of the dwellings (TMC 13.06.080.A.4.g). |
| Min Lot Size | None. ADUs are permitted on any legally established lot regardless of size or width (TMC 13.06.080.A.5.a). ADUs count toward UR density, but legal lots of record as of Feb 1, 2025 may hold at least 4 dwellings in UR-1, 6 in UR-2 and 8 in UR-3, so a house plus two ADUs fits on any existing lot (TMC 13.06.020.F.1). |
Permit Process & Fees [7][8][9][10][11][12][13][14]
An ADU permit in Tacoma goes through a standard permit review. 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. Permit 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.
| Approval Process | Residential new-construction building permit from Planning and Development Services, applied for online through the Accela portal at tacomapermits.org. The combined permit covers building, plumbing, mechanical and site development; electrical is a separate permit from Tacoma Power, and side-sewer, water and stormwater permits are added as the scope requires. Optional DADU coaching: file a PRE request for staff feedback on land use, building and site development, with a site visit, before you apply (TMC 13.06.080.A.3; PDS ADU pages). |
| Review Timeline | 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. |
| Permit 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. |
| 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. |
| 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. |
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Construction Costs [15][16][17]
Building an ADU in Tacoma typically costs $150,000-$350,000 ($300-$520 per sq ft); a garage conversion runs $75,000-$180,000.
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| Average Build Cost | $150,000-$350,000 |
| Cost per Sq Ft | $300-$520 |
| Garage Conversion | $75,000-$180,000 |
| Prefab ADU (Installed) | $170,000-$340,000 |
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Rental Income Potential [18][19]
A 2-bedroom ADU in Tacoma rents for around $1,780-$2,500/mo, an estimated 6-9% gross yield (e.g. $1,700/mo on a $250,000 build is about 8% before vacancy, taxes and the impact fee).
| Avg Rent (1 Bedroom) | $1,450-$2,050/mo |
| Avg Rent (2 Bedroom) | $1,780-$2,500/mo |
| 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). |
| Est. Annual ROI | 6-9% gross yield (e.g. $1,700/mo on a $250,000 build is about 8% before vacancy, taxes and the impact fee) |
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Recent Law Changes
What's Changed Recently
- June 1, 2026: Tacoma began collecting transportation impact fees (TMC 10.31, Ord. 29082, passed Dec 9, 2025). ADUs are charged 50% of the single-family rate for their district and the fee is due before the building permit issues.
- Feb 1, 2025: Home In Tacoma Phase 2 (Ord. 28986, passed Nov 19, 2024) replaced the R-1/R-2/R-3 zones with UR-1/UR-2/UR-3, moved the ADU standards to TMC 13.06.080.A, made detached ADUs a 'Backyard Building' housing type, and allowed accessory structures existing on Feb 1, 2025 to convert to ADUs regardless of setbacks or height.
- June 24, 2025 (Ord. 29042) and Dec 2, 2025 (Ord. 29076, effective Jan 5, 2026): annual and Tideflats amendments touched TMC 13.06.080, but the ADU rules (2 per lot, 1,000 sq ft, no parking, no owner-occupancy) did not change.
- RCW 36.70A.681 (HB 1337, 2023) sets the state floor: two ADUs per lot, at least 1,000 sq ft, no owner-occupancy, no parking within 1/2 mile of a major transit stop, impact fees capped at 50% of the principal unit, condo sale allowed. EHB 1345 (2026) applies only outside urban growth areas and does not touch Tacoma.
- Sept 2026: the PDS ADU Tip Sheet still prints the pre-2025 standards (rear-yard placement, 5/8-ft side and 15-ft rear setbacks); the controlling text is now TMC 13.06.080.A plus the UR district table in TMC 13.06.020.F.
Tips for Building an ADU in Tacoma
- Cost basis: 2026 industry guides for Tacoma/Pierce County put a detached ADU at $150,000-$350,000 for 500-900 sq ft ($300-$520/sq ft all-in), a garage conversion at $75,000-$180,000 and a prefab unit at $170,000-$340,000 installed. Seattle-area guides run $400-$650/sq ft, so treat these as a floor, not a quote.
- Height trap: in UR-1 and UR-2 the limit drops to 25 ft within the rear 25 ft of the lot, exactly where a DADU usually sits. You get 35 ft back by retaining a 12-in DBH tree (TMC 13.06.020.F.3) or, as an owner-occupant earning up to 150% of Pierce County median income, by recording a 5-year owner-occupancy covenant (TMC 13.06.020.F.5).
- Existing garage or shed on the lot as of Feb 1, 2025? It can be converted to an ADU regardless of setbacks, location or height, provided it meets the current Building Code and gets a pedestrian walkway (TMC 13.06.080.A.4.i).
- Every ADU gets its own Tacoma Power meter (TMC 12.06A.380): budget $970-$1,797 for the power connection, $176 to keep the ADU on the house's water meter (plus $850 if the meter must grow), or $5,922-$10,272 for a separate water service (TPU rates in effect Apr 7, 2025).
- Impact-fee deferral: a single-family or attached residential permit can defer the transportation impact fee to final inspection or 18 months, against a lien and an administrative fee (TMC 10.31.130). Ask PDS for the ADU rate for your district before you apply; the Rate Study table sets it.
- Amenity space and trees: the lot must keep 10% (UR-1), 7.5% (UR-2) or 5% (UR-3) of its area as amenity space and meet a tree-credit target of 30/25/20% canopy equivalent, or pay tree fees (TMC 13.06.020.F.1).
- Any ADU with its own entrance needs a walkway of distinct material to the sidewalk and an address visible from the street (TMC 13.06.080.A.4.e, A.5.e); parking, if you add it, goes at the rear off the alley.
ADU Builders in Tacoma
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Sources & References
All data on this page is sourced from official government records and verified market data. View our full methodology.
- Tacoma Municipal Code Title 13, Land Use Regulatory Code (City Clerk PDF, updated 01/2026; read via Wayback capture 2026-03-08): TMC 13.06.080.A, 13.06.020.F, 13.06.100.F.4.b, 13.06.090.C fn 17 Municipal Code — Accessed 2026-09-20
- Amended Substitute Ordinance No. 28986, Home In Tacoma Phase 2 (passed Nov 19, 2024; effective Feb 1, 2025), Tacoma Legistar ordinance — Accessed 2026-09-20
- Tacoma Legistar: Ord. 29042 (2025 Minor Code Amendments, passed Jun 24, 2025) and Ord. 29076 (Tideflats TMC 13 amendments, passed Dec 2, 2025, effective Jan 5, 2026) ordinance — Accessed 2026-09-20
- RCW 36.70A.681, Accessory dwelling units, regulation (2023 c 334 s 4) Government Data — Accessed 2026-09-20
- Accessory Dwelling Units, Tacoma Permits (PDS) Planning Department — Accessed 2026-09-20
- Accessory Dwelling Units Tip Sheet, Tacoma Permits (pre-2025 standards; superseded by TMC 13.06.080.A) Planning Department — Accessed 2026-09-20
- PDS Fee Estimator (informational), Tacoma Permits Planning Department — Accessed 2026-09-20
- Permit Timeline, Tacoma Permits (Oct 1, 2025 - Mar 31, 2026 snapshot) Planning Department — Accessed 2026-09-20
- Pre-approved Detached Accessory Dwelling Units (DADUs) tip sheet, Tacoma Permits Planning Department — Accessed 2026-09-20
- Pre-approved DADU Plan Options (Units A-D), Tacoma Permits Planning Department — Accessed 2026-09-20
- Detached Accessory Dwelling Unit (DADU) Coaching tip sheet, Tacoma Permits Planning Department — Accessed 2026-09-20
- Transportation Impact Fees tip sheet G-705 (May 2026), Tacoma Permits Planning Department — Accessed 2026-09-20
- Ordinance No. 29082, TMC 10.31 Transportation Impact Fees (passed Dec 9, 2025; effective June 1, 2026), Tacoma Legistar ordinance — Accessed 2026-09-20
- Utilities Considerations for Accessory Dwelling Units (Tacoma Power / Tacoma Water rates in effect Apr 7, 2025) Planning Department — Accessed 2026-09-20
- ADU Wizard, How Much Does an ADU Cost in Washington in 2026? (Tacoma/Pierce ranges) industry — Accessed 2026-09-20
- Tacoma DADU, How Much Does it Cost to Build a DADU in Tacoma? (June 1, 2026) industry — Accessed 2026-09-20
- Ballard Backyard Cottages, Cost to Build a DADU in Seattle (2025-2026 Update) industry — Accessed 2026-09-19
- HUD FY2027 Fair Market Rents, Tacoma, WA HMFA (Pierce County) Government Data — Accessed 2026-09-20
- HUD FY2027 Small Area Fair Market Rents, Tacoma ZIP codes Government Data — Accessed 2026-09-20
- Accessory Dwelling Units, Tacoma Permits (PDS) Planning Department — Accessed 2026-09-20
- RCW 36.70A.681, Accessory dwelling units, regulation Government Data — Accessed 2026-09-20
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