Can I Build an ADU in Spokane Valley, WA? (2026 Rules)

Yes, you can build an ADU in Spokane Valley. Washington’s HB 1337 applies to Spokane Valley as a fully-planning GMA city, which means the city must allow up to two ADUs per residential lot as a matter of right. Here’s what the local rules say and what to expect from the permit process.

Spokane Valley’s ADU Rules at a Glance

Spokane Valley allows both attached and detached ADUs in most residential zones. Here’s what the local standards look like for a detached backyard unit.

Number of ADUs Per Lot

Under state law, Spokane Valley must allow two ADUs per lot in any combination of attached and detached. That’s the protected floor set by HB 1337.

Maximum Size

Spokane Valley’s local code caps detached ADUs at 1,000 square feet or 60% of your primary home’s living area, whichever is smaller. On a 1,500 sq ft home, that works out to a 900 sq ft detached ADU maximum. On a home larger than 1,667 sq ft, the 1,000 sq ft cap applies.

Height Limit

Detached ADUs in Spokane Valley are generally limited to 16 feet in height. Check with the city if your design runs taller, as some flexibility may apply depending on the specific design and location.

Setbacks

Setback requirements vary by zoning district in Spokane Valley. Confirm your specific zone’s rear and side yard setbacks with Community Development before finalizing your site plan.

Parking

One additional off-street parking space may be required for your ADU. Exceptions apply if your property is near a major transit stop. Confirm current parking requirements with the city since state law limits how strictly they can enforce this.

Owner Occupancy

No owner-occupancy requirement applies to ADUs in Spokane Valley for standard long-term rentals. State law under HB 1337 prohibits cities from requiring it.

A Note on HOAs in Spokane Valley

HOA CC&Rs are common in Spokane Valley neighborhoods and frequently include restrictions on exterior structures, fences, and design. Washington law protects you from new HOA restrictions adopted after July 23, 2023, but pre-existing covenants may still apply.

Before you start designing, pull your CC&Rs and check for any language about accessory structures or secondary dwellings. If your HOA formed after July 2023, those new rules can’t restrict ADU construction.

What You Can Build

Most Spokane Valley homeowners looking to add a detached ADU are working with one of these configurations:

• A backyard cottage up to 1,000 sq ft (or 60% of your home’s size, whichever is smaller)
• A detached studio or one-bedroom unit for a tenant or family member
• A garage-plus-living unit, combining storage or parking with a separate dwelling space

Kit Culture’s kit homes and our upcoming ADU-specific models are designed to fit within Spokane Valley’s local size limits and arrive with permit-ready engineer-stamped drawings. Learn more about what a kit home includes.

Also in the area: Spokane ADU Permit Guide (2026)  •  Liberty Lake ADU Rules (2026)