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Port Townsend, WA Accessory Structures: ADU Rules (2026)

Some Restrictions

Compiled from the official code textEditor Martyn O'NeillLast verified August 2026

ADU rules in Port Townsend, WA, also called accessory dwelling unit regulations or granny flat ordinances, cover setbacks, owner-occupancy, parking, and permit requirements.

Key Facts

Units allowed per lot: Up to two ADUs
Size cap per ADU: 1,000 sq. ft.
Short-term rental: Prohibited in main or ADU
Occupancy proof: Certificate of occupancy required
Governing code: PTMC 17.16.020

ADU Eligibility Quick-Check

An Accessory Dwelling Unit (ADU) is a smaller, independent living unit on the same lot as a single-family home: converted garages, detached cottages, basement or attic conversions, and attached additions all qualify. Most states have streamlined ADU permitting since 2020, but local rules still control size, height, and setback.

Is your lot zoned single-family or multi-family residential?
Does your lot have at least 1,200 sq ft of buildable space?
Is your existing home owner-occupied (in most states this is not required, but some require it for ADU permits)?
Will the ADU stay under your state's size cap (commonly 850-1,200 sq ft for detached)?
Can you provide one off-street parking space (waived in many states within 0.5 mi of transit)?

If you answered 'yes' to most of these, you likely qualify in Washington under recent ADU streamlining laws. The Port Townsend, WA rules below cover local size, height, and setback requirements.

Summary

Port Townsend allows up to two accessory dwelling units per single-family lot, each capped at 1,000 square feet, but neither can be rented short-term.

Two accessory dwelling units (ADU) may be established as an accessory use to a single-family detached, shotgun house, duplex, triplex, or townhome residence provided the following conditions are continuously met:
1. A certificate of occupancy pursuant to the currently adopted city construction codes shall be obtained from the building official and posted within the ADU. The code inspection and compliance required to obtain a certificate of occupancy in an existing building shall be restricted to the portion of the building to be occupied by an ADU and shall apply only to new construction rather than existing components, except that any high hazards (i.e., smoke detectors, fire exits, stairways, LP gas appliances and fire separation) shall be corrected. Where additional fire separation is unduly burdensome, the building official may authorize a fire alarm system in lieu of required fire separation.
2. Neither the main nor accessory dwelling units shall be used as a short term rental, except as provided for in PTMC 17.57.020(B)(2).
3. ADUs established in an outbuilding shall not exceed 1,000 square feet in floor area and ADUs established within or attached to the primary residence shall not exceed 1,000 square feet, and under no circumstance shall the total lot coverage of the primary residence along with the ADU exceed the standard allowed in the underlying zoning district.

View official code

Official source re-checked September 8, 2026: no newer edition of the code had been published (publisher’s edition: current through Ordinance 3364, passed May 18, 2026).

Full Breakdown

PTMC 17.16.020(C) permits two ADUs as an accessory use to a single-family detached, shotgun, duplex, triplex, or townhome residence. Each ADU, whether in an outbuilding or attached to the primary residence, is capped at 1,000 square feet, and combined lot coverage of the house plus ADU still can't exceed the underlying zoning district's standard. A certificate of occupancy from the building official must be obtained and posted inside the unit before it's used. ADUs can even go in a legal nonconforming residence or a nonconforming setback situation if entrances stay at least 5 feet from property lines and nearby side windows are glazed with translucent material.

Violations & Fines

Occupying an ADU without a posted certificate of occupancy, exceeding the 1,000-square-foot cap, or renting either unit short-term violates PTMC 17.16.020 and is enforced as a zoning code violation by the building official.

Frequently Asked Questions

Can I rent my Port Townsend ADU on Airbnb?

No. PTMC 17.16.020(C)(2) bars both the main house and the ADU from short-term rental use, with a narrow exception under PTMC 17.57.020(B)(2).

How big can a Port Townsend ADU be?

Up to 1,000 square feet, whether it's a detached outbuilding or attached to the primary residence, per PTMC 17.16.020(C)(3).

Sources & Official References

[1]Port Townsend Municipal Code 17.16.020

Other rules in Port Townsend

Noise Ordinances: Construction HoursSome Restrictions Shed & Carport RulesSome Restrictions ADU Rental RestrictionsHeavy Restrictions Tiny HomesSome Restrictions ADU Impact FeesFew Restrictions Parking Rules: Abandoned VehiclesSome Restrictions Fence Regulations: Retaining WallsSome Restrictions Fence Regulations: Material RestrictionsSome Restrictions Animal Ordinances: Wildlife FeedingSome Restrictions Fire Regulations: Wildfire ZonesSome Restrictions

All Port Townsend rules

How Port Townsend compares: Easiest Cities to Build an ADU·Compare Port Townsend to another location·View the Washington accessory structures overview

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