Spokane Valley, WA Accessory Structures: ADU Rules (2026)
ADU rules in Spokane Valley, WA, also called accessory dwelling unit regulations or granny flat ordinances, cover setbacks, owner-occupancy, parking, and permit requirements.
Key Facts
- ADUs allowed per lot
- One, attached or detached
- Maximum size
- 50% of primary home's habitable area
- Minimum size
- 300 square feet
- Footprint cap
- 10% of lot or 1,000 sq ft, greater
- Bedroom limit
- Two bedrooms maximum
- Parking
- One additional off-street space required
Summary
Spokane Valley allows one accessory dwelling unit per lot, attached or detached, under SVMC § 19.40.030. The ADU cannot exceed 50 percent of the primary home's habitable floor area, must be at least 300 square feet, and its footprint is capped at 10 percent of the lot or 1,000 square feet, whichever is greater. The unit cannot have more than two bedrooms.
An ADU may be developed in conjunction with either an existing or new primary dwelling unit; ... One ADU, attached or detached, is allowed per lot; and one off-street parking space for the ADU is required in addition to the off-street parking required for the primary dwelling unit. ... The ADU shall not exceed 50 percent of the habitable square footage of the primary dwelling unit, nor be less than 300 square feet; ... The footprint of the ADU shall not exceed 10 percent of the lot area or 1,000 square feet, whichever is greater; and the ADU unit shall not have more than two bedrooms. ... ADUs shall be located behind the front building setback line and placed on a permanent foundation; ... ADUs shall not be allowed on lots containing a duplex, multifamily dwelling, or accessory apartment contained within the principal structure.
Full Breakdown
40 SVMC treats an accessory dwelling unit as a small second home attached to or standing apart from the primary residence. The ADU must be designed to look like part of the same single-family home: the code requires it to match the primary dwelling in exterior finish materials, roof pitch, trim, and window proportion and orientation. If the ADU is attached, its entrance has to sit on the side or rear of the structure, or otherwise be unobtrusive from the street, and only one entrance on the front facade of the primary dwelling is allowed so the property still reads as a single-family home.
70-1. A homeowner can convert an existing detached garage, shop, or other accessory structure into a detached ADU, provided it is brought up to the same development standards, including those setbacks. The ordinance blocks ADUs on lots that already carry a duplex, a multifamily building, or an accessory apartment inside the main house, since the intent is one additional unit per lot, not a second round of density. 040 and follow their own rules, including a 10-unit cap per site and a conditional use permit, rather than the residential standards summarized here.
Violations & Fines
Noncompliance with these siting, design, or size limits is grounds for revoking the ADU's approval under SVMC § 19.40.030(D)(4), and the City can order removal or conversion of a nonconforming unit back to its unregistered accessory-structure status. Because ADUs are tied to the building permit for the structure, disputes and enforcement proceed through the City's general code compliance process in Chapter 17.100 SVMC once an inspector or a neighbor complaint identifies a departure from the approved plans.
Frequently Asked Questions
How big can an ADU be in Spokane Valley?
Do I need extra parking for an accessory dwelling unit?
Can I build two ADUs on one lot in Spokane Valley?
Does my ADU have to match my house's exterior?
Sources & Official References
Other rules in Spokane Valley
How Spokane Valley compares: Easiest Cities to Build an ADU·Compare Spokane Valley to another location·View the Washington accessory structures overview
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