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Pasco, WA Accessory Structures: ADU Rules (2026)

Some Restrictions

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

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

Key Facts

ADUs per parcel: 1 attached or 1 detached, not both
Maximum size: 1,000 sq ft or 55% of primary home, whichever less
Maximum height: 25 ft or height of primary home, whichever less
Detached separation: 10 ft from principal dwelling, 6 ft from other accessory structures
Occupancy rule: Long-term only, over 180 days/year, no short-term rental
Permit process: Ministerial/administrative, no public hearing

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 Pasco, WA rules below cover local size, height, and setback requirements.

Summary

Pasco allows one attached or one detached ADU on any residential lot with a legal single-family home, processed as a ministerial or administrative permit with no public hearing. Size is capped at 1,000 square feet or 55 percent of the primary home, whichever is less, with a 25-foot height limit.

Number of ADUs Per Parcel. A maximum of one attached or one detached ADU is permitted on residential parcels with legally permitted and conforming single-family dwellings; provided, that all the requirements of the PMC and applicable development regulations are met. ... Unit Size. The size of the ADUs shall not exceed 1,000 square feet or 55 percent of the total square footage of the primary residence or dwelling, whichever is less. Unit Height. The maximum height of the ADU shall be no taller than that of the principal dwelling or 25 feet, whichever is less.

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 4837, passed May 4, 2026).

Full Breakdown

020 permits ADUs in all residential zoning districts on parcels with a legally conforming single-family home. 030). 040(5)(b)-(c)). 040(5)(d)-(e)). 040(5)(f)). 040(3)(b) bars short-term or vacation rental use and requires occupants to reside more than 180 days per calendar year. 161 instead.

Violations & Fines

Building more than one ADU per parcel, exceeding the 1,000-square-foot/55-percent size cap, or using an ADU for short-term or vacation rental in violation of the 180-day residency rule under PMC 25.161.040(3)(b) are reported to and enforced by the Pasco Code Enforcement Hearings Board (PMC 25.161.040(3)(c)). An ADU built without a permit is treated as prima facie evidence of a violation once the City shows by a preponderance of the evidence that it lacks one, rebuttable only by proof no permit was required when it was built (PMC 25.161.040(6)(f)(i)).

Frequently Asked Questions

How many ADUs can I build on one lot in Pasco?

Only one. PMC 25.161.040(1) caps every residential parcel with a legally conforming single-family home at a maximum of one attached ADU or one detached ADU, not both.

How big can a Pasco ADU be?

Up to 1,000 square feet, or 55 percent of the primary residence's total square footage, whichever is smaller, per PMC 25.161.040(5)(b). Height is capped at 25 feet or the height of the primary dwelling, whichever is less.

Can I rent my Pasco ADU on Airbnb?

No. PMC 25.161.040(3)(b) restricts ADU occupancy to long-term residential use and requires occupants to live there more than 180 days per calendar year, expressly barring transient and short-term/vacation rental use.

Sources & Official References

Other rules in Pasco

Parking Rules: Overnight ParkingSome Restrictions Shed & Carport RulesSome Restrictions Parking Rules: RV & Boat ParkingSome Restrictions ADU Rental RestrictionsSignificant Restrictions ADU Owner OccupancyLight Restrictions Noise Ordinances: Decibel LimitsSome Restrictions Parking Rules: Abandoned VehiclesSignificant Restrictions Parking Rules: Driveway RulesSome Restrictions Fence Regulations: Fence Permit RequirementsLight Restrictions

All Pasco rules

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

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