Research by DoINeedAPermit Research Team · Updated May 2026
The Short Answer
Spokane Valley requires a building permit for every ADU—detached, garage conversion, junior ADU, or attached. Washington state law (RCW 36.70A.696) waives owner-occupancy rules, but the city still requires full plan review, inspections, and compliance with setbacks, utilities, and egress.
Spokane Valley adopted a formal ADU ordinance in 2019 and revised it in 2023 to align with Washington state's aggressive ADU-enablement laws. Unlike some Washington cities that buried ADU rules in general residential code, Spokane Valley published a dedicated ADU chapter with explicit standards for detached, garage-converted, and attached units. The city's online permit portal requires you to select 'ADU' as a project category, triggering a streamlined plan-review track—if your project hits the pre-approved checklist, you can often get over-the-counter approval in 1-2 weeks instead of the standard 4-6 week review. Critically, Washington state law (RCW 36.70A.696, effective 2023) prohibits cities from requiring owner-occupancy, so you can rent out a detached ADU on your primary residence without triggering additional zoning restrictions. However, Spokane Valley does enforce setback rules (typically 5 feet for detached ADUs on residential lots), lot-coverage caps, and parking waivers only for owner-occupied units—if you plan to rent, you may face parking requirements. The city's permit fee for an ADU averages $4,500–$8,000 (plan review + building permit + planning review bundled), and the city publishes a fee schedule online. You'll need full inspections: foundation (if detached), framing, electrical, plumbing, rough-in HVAC, insulation, drywall, final, and planning sign-off.

What happens if you skip the permit (and you needed one)

Spokane Valley ADU permits — the key details

Washington state law (RCW 36.70A.696, codified in Spokane Valley Municipal Code Section 17.33) requires cities to allow ADUs on any single-family residential lot. Spokane Valley's 2023 update eliminated owner-occupancy requirements statewide, meaning you can legally rent out a detached ADU without converting the primary residence into a rental. However, this does NOT mean the city waives all restrictions—setbacks, lot coverage, egress, utilities, parking, and fire-separation still apply. A detached ADU on a typical Spokane Valley residential lot (6,000–8,000 sq ft) must be set back at least 5 feet from side and rear property lines, and it cannot exceed 25% of the lot's area or 1,200 square feet, whichever is smaller (unless the lot is larger than 10,000 sq ft, which relaxes the cap to 1,500 sq ft). The city's ADU ordinance explicitly allows garage conversions—converting an existing detached garage into a habitable ADU—and these are often the fastest-track projects because the foundation and roof are already in place; you only need to address insulation, egress (via a window or door), kitchen facilities (sink, stove, refrigerator), and separate utilities. Junior ADUs (ADUs carved out of the primary dwelling, sharing utilities and entry) are NOT permitted in Spokane Valley; only fully independent units with separate entrances and utilities qualify.

Egress is the most common rejection point in Spokane Valley ADU permits. Washington's 2023 ADU laws require every ADU to have a bedroom meeting IRC R310 (which mandates a second means of escape—either a window with a minimum 5.7 sq ft opening and a sill no higher than 44 inches, or a second exit door). This is NOT optional: Spokane Valley inspectors will fail framing if a bedroom lacks compliant egress. For a detached ADU, you'll need either two exterior doors or one door + one compliant window; for a garage conversion, the conversion almost always requires adding a window to the bedroom (because the garage door opening does not count as a second means of escape). If your lot is on a hillside or in a zone with high groundwater (common in the Spokane Valley alluvial belt near the Spokane River), a basement bedroom may not qualify for an egress window (because the window opening would be below grade); in these cases, you'll need a full second exit door or be limited to a one-bedroom ADU with egress only via the main entry. Spokane Valley's building department publishes a checklist on its portal—request it before you start design to avoid costly revisions.

Utilities and separate metering are mandatory for all ADUs in Spokane Valley. You cannot share a water meter with the primary dwelling; the ADU must have its own meter or a separately billed sub-meter approved by the Spokane Valley Water District. Electrical service must be sub-metered or separately served (a new breaker panel fed from a second service or a sub-panel with its own revenue meter). Sewer is typically shared (the ADU drains to the primary home's sewer line), but you'll need to submit a plumbing plan showing the tie-in point and slope. Gas, if used, must be separately metered. These utilities are not optional: the city's electrical and plumbing inspectors will reject a final permit if a separate utility connection is not shown on the plans. Spokane Valley Water District charges a connection fee (typically $1,500–$3,000 for a new meter), and Avista Utilities charges for a new electrical service or sub-meter (typically $2,000–$4,000). Budget these into your project cost.

Parking waivers in Spokane Valley are partial and conditional. State law (RCW 36.70A.696) allows cities to waive parking for owner-occupied ADUs, and Spokane Valley's ordinance does waive on-site parking if the ADU is owner-occupied and the lot is within one-quarter mile of a transit stop (though Spokane Valley Transit service is limited outside downtown and the commercial corridors). If you're renting out the ADU or the lot is not near transit, the city typically requires one off-street parking space on the property (in addition to primary dwelling parking). This is enforceable via deed restriction; if you later decide to rent the ADU, you must ensure the parking space remains available. Detached ADUs can share a driveway with the primary dwelling, but you cannot count street parking or eliminate primary-dwelling parking to satisfy the ADU requirement. For lots with limited space (common in Spokane Valley's older neighborhoods), this parking rule is a major constraint—plan your site layout early to confirm a second parking space fits.

Spokane Valley's permit timeline and online portal are a major advantage for ADU projects. The city's permit system (accessible via the Spokane Valley city website) allows you to pre-upload plans and trigger an initial 'soundness' check before you formally submit. If your design hits the city's ADU pre-approved checklist (detached, <1,200 sq ft, 5+ ft setback, egress window shown, utilities diagrammed), you can often get 'over-the-counter' approval—no formal plan review, just a 1-week turnaround. Full review (if your lot is non-standard, the ADU exceeds the 1,200 sq ft threshold, or you're converting a garage with unusual constraints) takes 4–6 weeks. The city applies a 60-day shot clock once you pay the permit fee and submit complete plans, though 'complete' is strictly interpreted—missing utility diagrams or egress details will restart the clock. Most contractors recommend submitting plans to the city's planning department 2 weeks before the building department to catch zoning issues (setbacks, lot coverage) early and avoid simultaneous rejections from both divisions.

Three Spokane Valley accessory dwelling unit (adu) scenarios

Scenario A
Detached ADU, 800 sq ft, 2 bedrooms, owner-occupied — typical 7,500 sq ft lot in Spokane Valley residential area (Hangman Valley, Holmberg, Applegate neighborhood)
You own a single-family home on a 7,500 sq ft lot in Hangman Valley and plan to build a detached ADU in the rear yard. Your lot is not in a historic district, not near a floodplain, and not subject to HOA restrictions (confirm with county assessor). You plan a 800 sq ft, 2-bedroom ADU with a separate entrance, full kitchen, and one bathroom. The detached building will be set 8 feet from the rear property line and 10 feet from the side line (exceeds Spokane Valley's 5-foot minimum). Your frost depth is approximately 30 inches (east side of Spokane Valley, glacial till soil typical of the area); you'll need a rubble trench or concrete stem-wall foundation rated for frost depth. You hire a local architect to prepare plans showing IRC R310 egress (one bedroom with 5.7 sq ft window + second exit via main entry door), separate electrical sub-meter, new water meter, and gravity sewer tie-in to primary dwelling. You submit plans to Spokane Valley permit portal and request pre-approval review. Because your design hits the checklist (detached, <1,200 sq ft, compliant egress, utilities shown), the city approves over-the-counter in 8 business days. Permit cost is $4,200 (building permit $1,800 + planning review $800 + expedite fee $400 to jump the queue, optional). You pull the permit, hire a contractor (you're not owner-building because you don't live in the ADU), and begin work. Inspections run: foundation (Week 1), framing (Week 3), mechanical/electrical/plumbing rough (Week 5), insulation/drywall (Week 6), final + fire marshal egress check (Week 8). Total timeline: 10 weeks from permit to occupancy. Water District charges $2,000 meter connection; Avista charges $2,500 for sub-meter service upgrade. Total hard costs (design, permit, utilities, construction) approximately $150,000–$200,000 depending on finishes and site prep.
Permit required | Over-the-counter pre-approval available | Separate water meter + electrical sub-meter required | Frost depth 30 inches (rubble trench or stem wall) | 8 business days to approval | $4,200 permit + $4,500 utility connections | Total project $150,000–$200,000
Scenario B
Garage conversion to ADU, 600 sq ft, 1 bedroom + open living — North Spokane Valley (near Pines Road), owner plans to rent it out
Your garage is a detached structure (16×24 ft, roughly 385 sq ft of floor space) on a 6,000 sq ft residential lot in North Spokane Valley, two blocks from a transit stop served by Spokane Valley Transit (Route 31, hourly service). You plan to convert it into a 1-bedroom ADU (sleeping room 12×14 ft, living/kitchen/bath 10×16 ft open plan). The lot is within city limits, not in a flood zone, and you intend to rent the ADU out—meaning it does NOT qualify for owner-occupancy parking waivers. Spokane Valley's ADU code explicitly allows garage conversions, but your lot is only 6,000 sq ft; adding a 600 sq ft ADU brings total living space to approximately 2,200 sq ft on a 6,000 sq ft lot (36.7% coverage), just shy of Spokane Valley's 25% cap for lots under 10,000 sq ft. You contact the planning department and are told you need a variance OR a lot-coverage exception if the existing primary residence is already larger than 1,500 sq ft. You request the property assessment; the primary home is 1,650 sq ft, so the combined footprint exceeds the cap. Spokane Valley planning tells you: you can either (1) pursue a variance (adds 4–6 weeks, $500–$800 filing fee, minor risk of denial), or (2) reduce the ADU to 550 sq ft (staying under the cap), or (3) if the property qualifies as 'infill' or 'urban lot' under recent city policy, seek an administrative exception (1–2 weeks, $300 fee, high approval rate). You choose option (3): the lot is in an infill area per city definition. Approval comes in 10 days. Next, you design the conversion: existing garage slab is concrete (frost-protected because the garage has existed for 20+ years and is in-ground; you don't need to replace the foundation). You add insulation to the slab, frame new interior walls, install a egress window in the sleeping room (5 ft × 3 ft, rated for IRC R310), add a separate entry door from the driveway side, and carve out a galley kitchen (sink, electric cooktop, refrigerator) and a 3/4 bathroom. You separate the electrical: the garage was on the primary home's panel; you run a new sub-meter panel from the main service (or add a separate meter if the utility distance is short). Water and sewer: you'll likely re-run the water line to a sub-meter, and sewer will tie into the primary home's line. You'll need parking: because you're renting, Spokane Valley requires one off-street space. Your driveway is 16 ft wide; you can fit one compact car space beside the converted garage. You submit plans to the building department showing egress, utilities, parking, and lot coverage exception approval. Building permit is $3,800 (slightly higher because of the variance/exception paperwork). Avista charges $1,800 to add a sub-meter to the existing service (cheaper than a new service because the garage is only 20 ft from the main panel). Water District sub-meter is $1,200. Total permit + utility costs: approximately $6,800. Inspections: foundation/slab prep (no work required, grandfathered), framing (interior walls + egress window), electrical sub-meter + rough wiring, plumbing rough (sink, toilet, shower), mechanical (usually not required for units <1,000 sq ft without heating ducts, but HVAC rough if you're adding a mini-split or ductless system), insulation/drywall, final. Timeline: 8 weeks from permit to occupancy because the slab and roof are already there. Total project cost (design, permits, conversion, utilities, finishes): approximately $80,000–$120,000.
Permit required | Garage conversion allowed | Lot-coverage exception required ($300 admin fee) | 1-bedroom, separate entry, egress window mandatory | Rented = parking requirement enforced (1 space) | Separate electrical sub-meter + water sub-meter required | No foundation work (existing garage) | 8 weeks to completion | $3,800 permit + $3,000 utilities + $300 exception = $7,100 total fees | Project cost $80,000–$120,000
Scenario C
Above-garage ADU, 750 sq ft, 1 bedroom — attached to primary residence (secondary structure technically), Southwest Spokane Valley (Spokane County fringe, near Pines Road), owner-builder owner-occupant
You own a 1-acre lot on the Spokane County border within Spokane Valley city limits (just annexed into city in 2021). You plan to build an accessory dwelling above a detached garage structure: first floor is a 2-car garage (500 sq ft), second floor is the ADU (750 sq ft, 1 bed + full bath + living/kitchen). This is technically an 'accessory structure with habitable space above,' not a pure detached ADU, but Spokane Valley's 2023 ADU code explicitly allows it under the rubric of 'accessory structures containing ADU space.' You are the owner-occupant (you'll live in the primary residence and rent the above-garage unit), so you qualify for owner-builder exemption under Washington state law (RCW 19.27.015). You also qualify for parking waiver (owner-occupied) and lot-coverage exemption (1 acre lot far exceeds the 10,000 sq ft threshold). You draw plans yourself or hire a residential designer (not a licensed architect, to keep costs down). Your plans show: detached structure 24 ft × 32 ft footprint, 24-ft roof peak (within typical residential height limits), concrete stem-wall foundation on grade (frost depth 30 inches in your area, you use a rubble trench per local practice), 2×6 framing with R-19 wall insulation + R-38 ceiling for climate zone 5B (east-side Spokane Valley), vinyl siding, roof shingles. The upstairs ADU has one egress window in the bedroom (IRC R310 compliant: 5 ft × 3 ft, sill 30 inches, operable), plus a door to an external deck (second means of escape, meets egress requirements). You have separate electrical service for the ADU (sub-panel fed from a disconnect on the garage's detached service, or Avista could run a second meter for an extra $1,500). Water: Spokane Valley Water District allows you to sub-meter off a single main line, or you can run a second main (you choose sub-meter at $1,200). Sewer ties into the primary home's line. You contact the Spokane Valley building department pre-submission and ask about owner-builder status; they confirm that you (the owner-occupant) can pull the permit yourself and perform the work, though electrical rough and final must be inspected by a licensed electrician and plumbing must be inspected by a licensed plumber (you can do framing and finishes). You submit plans showing: foundation detail (rubble trench, frost depth 30 inches, typical for glacial-till area), floor plan with egress window dimensioned, electrical diagram (sub-panel location, egress light circuit), plumbing isometric (water sub-meter, sewer tie-in), and mechanical (ductless mini-split HVAC for the ADU, sized for 750 sq ft). Spokane Valley reviews in 14 days (not over-the-counter because you're owner-building and the department wants to confirm your qualifications, though this is routine). Permit issued at $2,800 (owner-builder fee is lower than contractor permit, typically 60–70% of the standard rate). You begin work in spring (frost depth requires grade work starting after winter frost heave subsides). Inspections: foundation (soils engineer or department inspector verifies frost-depth compliance and drainage), framing (walls, roof, egress window rough opening), mechanical/electrical/plumbing rough (licensed electrician + plumber), drywall, final (all trades). Timeline: 14 weeks (slower because owner-builder work typically proceeds in phases, not continuously). Total out-of-pocket: $2,800 permit + $1,200 water sub-meter + materials and labor (if you're doing framing/finishes yourself, $60,000–$90,000; if you hire labor, $120,000–$170,000).
Permit required | Owner-builder allowed (owner-occupant only) | Above-garage ADU explicitly permitted | Separate egress window mandatory | Frost depth 30 inches (rubble trench compliant) | Climate zone 5B insulation (R-19 walls, R-38 roof) | Owner-occupancy = parking waiver + coverage exemption | Separate water sub-meter required | Licensed electrician + plumber required for inspections | $2,800 permit fee (owner-builder rate) | $1,200 utilities setup | Project $60,000–$170,000 depending on labor

Every project is different.

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Frost depth, soil, and foundation requirements in Spokane Valley ADU projects

One underappreciated local factor in Spokane Valley ADU permits is the city's 2023 update aligning with Washington state law (RCW 36.70A.696). Older Spokane Valley homes (pre-2019) were often built under zoning codes that explicitly prohibited 'boarding houses' or 'multi-family-appearing structures' in single-family zones. If your lot was subject to a restrictive covenant or HOA rule banning ADUs, state law (2023 update) allows you to override the restriction IF the ADU is owner-occupied. However, if you plan to rent it out, the HOA restriction may still apply—this is a gray area that the state legislature left to local interpretation. Always check your title report and HOA documents before committing to an ADU project. If an HOA restriction exists and you're planning to rent, you may need an HOA variance (often requires 66% member vote) or you may need to apply for a zoning variance arguing the state law preemption. Spokane Valley Planning Division publishes guidance on this on their website; download the 'ADU Frequently Asked Questions' PDF (updated 2024) to confirm your situation. The bottom line: state law wins for owner-occupied ADUs, but HOA rules and covenants can still bite you if you plan to rent, so check early.

Utilities, sub-metering, and cost details for Spokane Valley ADUs

Practical budgeting for a Spokane Valley ADU includes soft costs often overlooked by first-time builders. A full ADU design (plans ready for permit) costs $3,000–$6,000 if you hire a residential designer (cheaper than an architect, sufficient for ADU standards). Permit costs, as noted above, run $2,500–$4,500 for full review. Utility connections (water sub-meter, electrical sub-panel or new service, sewer tie-in, gas if desired) total $4,500–$8,000. Pre-permit surveying (to verify setbacks, lot coverage, easements) costs $1,500–$2,500 for a residential ADU lot. Inspections are bundled into the permit fee, but expect scheduling delays in spring/early summer (Spokane Valley has seasonal demand peaks when foundation season starts); budget an extra 2–4 weeks if you're pulling a permit between April and June. Total soft costs: $12,000–$21,000 for a detached ADU, $8,000–$15,000 for a garage conversion. Hard costs (construction labor, materials, site prep, finishes) run $70,000–$200,000+ depending on finish quality and site constraints. The total project cost for a typical 800 sq ft detached ADU in Spokane Valley ranges from $120,000 (basic finishes, favorable soil conditions) to $250,000 (high-end finishes, complex site, new utility lines from street). For garage conversions, budget $80,000–$150,000. Rental income potential varies widely but typically ranges from $1,200–$1,600 per month in Spokane Valley (2024 market), depending on proximity to downtown and unit finishes—use the property calculator on Zillow or Apartments.com to validate local market rates before committing.

City of Spokane Valley Building Department
12002 E Mission Avenue, Spokane Valley, WA 99216
Phone: (509) 924-2635 | https://www.spokanevalleycity.org/building-permits/
Monday–Friday, 8:00 AM–5:00 PM (closed city holidays)

Common questions

Does Washington state law override Spokane Valley's parking requirement for ADUs?

Partially. Washington RCW 36.70A.696 (effective 2023) prohibits parking requirements for owner-occupied ADUs. Spokane Valley waives parking if the primary resident (you) also live in the primary dwelling and the ADU is owner-occupied. However, if you rent out the ADU, Spokane Valley may still require one off-street parking space—unless the lot is within one-quarter mile of frequent transit (Route 31 or other city transit). Check with Spokane Valley Planning to confirm transit proximity before relying on the parking waiver for a rental ADU.

Can I live in the ADU and rent the primary dwelling instead (switching occupancy)?

No. Washington state law and Spokane Valley code require the primary dwelling (the original single-family home) to be owner-occupied if you're claiming ADU parking and zoning waivers. You cannot swap and live in the ADU while renting the primary home—that converts the lot into a de facto duplex or rental property and violates single-family zoning. If you want to relocate, you must either (1) accept that the lot now has two rental units (requires zoning variance), or (2) sell one of the properties.

Is a junior ADU allowed in Spokane Valley?

No. Spokane Valley explicitly requires separate utilities (water meter, electrical service or sub-meter, sewer line tie-in) for all ADUs. Junior ADUs (units carved from the primary dwelling, sharing utilities and entry) are not permitted in the city. Washington state law allows junior ADUs, but Spokane Valley has not adopted them. You must build a fully independent ADU with a separate entrance and separate utility connections.

What is the frost depth in Spokane Valley, and how does it affect my ADU foundation?

Frost depth is 30 inches on the west side (Pines Road, Hangman Valley) and up to 36 inches east of downtown (Applegate, Holmberg). You must dig footings below the frost line per IRC R403.1. Most detached ADUs use a rubble trench (gravel-filled, open-bottom, frost-protected foundation) or a concrete stem wall to 30+ inches depth. Existing garage slabs that have been in place for many years are typically grandfathered as frost-protected and don't require replacement when converting to an ADU. Check with the building department if your site has unusual soils or alluvial groundwater.

Can I do the work myself as an owner-builder on my ADU in Spokane Valley?

Yes, if you're the owner-occupant of the primary residence and the ADU is for your own use. Washington state law (RCW 19.27.015) allows owner-builders to pull permits and perform work on their own owner-occupied homes. However, electrical rough-in and final inspection must be done by a licensed electrician, and plumbing rough and final must be done by a licensed plumber. Framing, insulation, drywall, and finishes can be owner-performed. If you plan to rent out the ADU, you must hire a licensed contractor—the owner-builder exemption does not apply to rental properties.

How long does a Spokane Valley ADU permit take from application to occupancy?

Standard review: 4–6 weeks to permit issuance, then 8–14 weeks of construction and inspections, totaling 12–20 weeks (3–5 months). If your design hits the city's pre-approved ADU checklist (detached, <1,200 sq ft, egress window shown, utilities diagrammed), you may qualify for over-the-counter approval in 1–2 weeks instead of full plan review. Always contact the planning department before finalizing design to confirm whether your project qualifies for expedited review.

Do I need a separate water meter for the ADU, or can I share the primary dwelling's meter?

You must have a separate water meter or a separately billed sub-meter. Spokane Valley Water District requires this for all ADUs to track individual fixture units and ensure code-compliant demand. You can either run a new water main line from the street (most expensive) or sub-meter off the primary home's line if it's oversized (cheaper). Water District charges $1,200–$2,000 for meter setup and connection, plus labor. This is a hard requirement; shared meters will cause permit rejection at the rough-plumbing inspection.

What setback does Spokane Valley require for a detached ADU?

Spokane Valley typically requires 5 feet minimum setback from side and rear property lines for detached ADUs. Front-yard setbacks must comply with the primary dwelling's setback (usually 15–25 feet from the street, depending on the neighborhood zone). If your lot is very small or irregularly shaped, you may not be able to fit a compliant detached ADU—contact Planning for a site-specific determination before investing in design. Some older Spokane Valley neighborhoods have non-standard setbacks; always verify lot dimensions and easements with a surveyor before committing.

If my property is in an HOA with deed restrictions against ADUs, can I override it under Washington state law?

Only for owner-occupied ADUs. Washington state law (2023) preempts local deed restrictions for owner-occupied ADUs—meaning you can legally build an ADU even if the HOA says no, as long as you live in the primary residence. However, if you plan to rent out the ADU, the HOA restriction may still apply; you would need an HOA variance (typically requires 66% member vote) or you could attempt to appeal the restriction as preempted by state law (risky and potentially expensive). Always review your CC&Rs before committing to an ADU project, and consult a real-estate attorney if HOA restrictions are unclear.

What is the maximum square footage for an ADU in Spokane Valley?

For lots under 10,000 sq ft: 1,200 sq ft maximum (or 25% of lot area, whichever is smaller). For lots 10,000+ sq ft: 1,500 sq ft maximum. Junior ADUs (not allowed in Spokane Valley) would be exempt, but all independent ADUs are capped at these thresholds. If your project exceeds the cap, you can pursue a variance (adds time and cost) or reduce the footprint. Garage conversions count toward the square footage cap; if your garage conversion plus lot coverage of the primary dwelling exceeds 25%, you'll need a lot-coverage exception.

Nearby cities & related guides

Accessory Dwelling Unit (ADU) Permits in Seattle, WA Accessory Dwelling Unit (ADU) Permits in Spokane, WA Accessory Dwelling Unit (ADU) Permits in Tacoma, WA
Disclaimer: This guide is based on research conducted in May 2026 using publicly available sources. Always verify current accessory dwelling unit (adu) permit requirements with the City of Spokane Valley Building Department before starting your project.

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