What Can You Build Without a Permit in Washington? (2026)
The 30-second answer for Washington
In Washington, the projects you can usually build without a building permit are a small detached shed, a short freestanding deck, a fence under the height cap, a low retaining wall, and cosmetic interior work. The exact limits Washington enforces are in the table below — and your city can be stricter than the state. The catch every homeowner needs to hear: even when no permit is required, the building code, zoning setbacks, and any HOA rules still apply. Permit-exempt means the paperwork is waived, not the rules.
How Washington sets the rules
Washington enforces a single mandatory statewide residential code: the 2021 International Residential Code as amended and adopted by the State Building Code Council under Chapter 51-51 WAC, with authority from RCW 19.27 and 70.92. It became effective in every Washington county and city on March 15, 2024. Local governments may add administrative amendments (and often make exemptions stricter) but cannot drop below this state minimum.
Permit-exempt limits in Washington
These are the thresholds we verified for Washington. Treat each one as the most you can usually do without pulling a permit — a stricter city amendment always wins.
| Project | Washington permit-exempt limit |
|---|---|
| Detached shed / accessory building | Statewide baseline (adopted 2021 IRC R105.2): no building permit for a one-story detached accessory structure (tool/storage shed, playhouse, similar) with floor area 200 sq ft or less. Seattle is stricter, exempting sheds only up to 120 sq ft and only on a slab-on-ground foundation. Zoning setbacks and lot-coverage limits always still apply. |
| Deck | Statewide baseline (2021 IRC R105.2): a deck is permit-exempt only if it meets ALL of these — 200 sq ft or less, no more than 30 inches above grade at any point, not attached to the dwelling, and does not serve the exit door required by Section R311.4. Seattle lowers the height trigger: any deck more than 18 inches above the ground (or any roof deck) requires a permit. |
| Fence | Statewide (2021 IRC R105.2): fences not over 7 feet high need no building permit. Zoning height caps still apply (commonly 6 feet in front/side yards). Seattle's own list exempts fences up to 8 feet from a building permit, but limits concrete or masonry portions to 6 feet. |
| Retaining wall | Follows 2021 IRC R105.2 with no state amendment: no building permit for a retaining wall 4 feet or less measured from the bottom of the footing to the top of the wall, unless it supports a surcharge (a slope, structure, or other load bearing on the wall). Seattle and Spokane both apply this 4-foot threshold. |
| Patio (on grade) | At-grade patios and concrete slabs on grade, plus sidewalks and driveways, are exempt statewide (2021 IRC R105.2; Seattle SDCI lists patios and concrete slabs on grade as not requiring a permit). Once a raised patio or platform rises above the deck height trigger (30 inches statewide, 18 inches in Seattle) it is treated like a deck. |
Baseline: 2021 International Residential Code, Section R105.2. See the national project-by-project guide for how each threshold works.
Can you do the work yourself in Washington?
Yes. A homeowner may pull the permit and do the work themselves on a residence they own and use; RCW 18.27.090 exempts owners from the state contractor-registration requirement. That exemption is lost if the work is done to sell, lease, or demolish the property. Anyone you hire for pay must be a Washington-registered contractor, and some jurisdictions require an owner-builder acknowledgment. Homeowners may also do their own electrical work under an L&I (or city) electrical permit.
What's different about Washington
One mandatory statewide code, but 'permit-exempt' still varies by city
The 2021 IRC (Chapter 51-51 WAC) is enforced in every Washington city and county, and the state did NOT amend R105.2, so the 200 sq ft shed / 30-inch deck baseline is the statewide floor. Home-rule cities can and do adopt stricter local thresholds, so a project that needs no permit in Spokane may require one in Seattle. Always confirm with the local building department.
Seattle is the strictest: 120 sq ft sheds and an 18-inch deck line
Seattle's residential code exempts detached sheds only up to 120 sq ft AND only on a slab-on-ground foundation, and it requires a permit for any deck more than 18 inches above grade, versus the state's 30 inches. Roof decks always need a permit. Sheds of 120-750 sq ft use Seattle's streamlined Subject-to-Field-Inspection permit.
Critical areas and shorelines cancel the exemption
Under Washington's Growth Management Act and Shoreline Management Act, cities overlay Environmentally Critical Areas (steep slopes, wetlands, streams, shorelines). Seattle SDCI states that low decks and small sheds lose their permit exemption if they are in or near an ECA. A separate review or permit is then required regardless of size or height, so permit-exempt never means critical-area-exempt.
"Permit-exempt" does not mean rule-free
I spent 25 years as a firefighter before I built PermitDeck, so let me be blunt about the part that gets people hurt. "No permit" never means "no rules." When a project is exempt in Washington, three things are still true — and now you are the one responsible for them, because no inspector is coming to check:
- Building code still applies. An exempt deck in Washington still has to meet the structural rules of IRC R507 — real footings, a proper ledger, and guards. A shed still has to carry your local snow and wind load. The code does not care whether a permit was pulled.
- Zoning and setbacks still apply. Exempt does not mean you can put it anywhere. Setbacks from property lines, easements, lot-coverage caps, and corner-lot sight lines all still bind you — and a neighbor complaint can force you to move it.
- HOA rules are separate. Your HOA architectural review is a private contract, not a government permit. You can be fully permit-exempt with your city and still be forced by your HOA to tear something out.
The big Washington cities
Permits are pulled locally, so your city's building department has the final word. Here are the two largest, with a link straight to their office.
Seattle
SDCI (Seattle Residential Code) exempts: detached sheds under 120 sq ft on slab-on-ground only; decks, platforms and walks less than 18 inches above grade and not over a basement/story; at-grade patios and concrete slabs; fences up to 8 ft (masonry portions max 6 ft); retaining walls 4 ft or less; and minor repairs of $6,000 or less per 6 months. Any environmentally critical area (ECA) overrides these exemptions.
Seattle building departmentSpokane
The City of Spokane adopts the 2021 IRC with no local amendment to R105.2, so the state baseline governs: sheds 200 sq ft or less, freestanding decks 200 sq ft or less and 30 inches or less above grade and not serving the exit, fences 7 ft or less, retaining walls 4 ft or less. An older 2009 Planning handout still cites a 120 sq ft shed figure; confirm 200 sq ft with the Permit Center. Zoning setbacks still apply.
Spokane building departmentTurns out you do need a permit? We'll match you with pros who pull it
If your project crosses one of these Washingtonthresholds, the cleanest path is to hire a licensed pro who pulls the permit in their own name and stands behind the inspection. Tell us the project once and we'll send it to up to three verified local pros. It's free, it's capped at three, and we never sell your information — the opposite of the lead-farm sites.
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What happens if you needed a permit and skipped it
Guessing wrong on the exemption is not a small risk. The common outcomes are a stop-work order, a fine (often double the normal permit fee), and being ordered to open finished work back up for inspection or tear it out. The expensive part usually lands later: unpermitted work routinely kills a home saleat the buyer's inspection, and an insurance claim can be denied if the damage traces back to unpermitted construction. Most jurisdictions do allow a retroactive (after-the-fact) permit — it costs more, but it clears the record.
Full detail: what happens if you build without a permit and how to get a building permit.
Washington permit-exemption FAQs
Can I build a shed without a permit in Washington?
In most of Washington, yes. The state's adopted 2021 IRC exempts a one-story detached shed of 200 square feet or less from a building permit. Seattle is stricter, exempting only sheds up to 120 square feet built on a slab-on-ground foundation. Everywhere, zoning setbacks, lot coverage limits, and any critical-area rules still apply, so check locally first.
How high can a deck be before I need a permit in Washington?
Statewide, a freestanding deck avoids a building permit only if it is 200 square feet or less, no more than 30 inches above grade at any point, not attached to the house, and does not serve the required exit door. Seattle lowers the trigger: any deck more than 18 inches above the ground needs a permit, and roof decks always require one.
Do I need a permit for a fence or retaining wall in Washington?
Under the adopted 2021 IRC, fences up to 7 feet high and retaining walls up to 4 feet (measured from the footing bottom to the wall top, with no surcharge) need no building permit. Zoning still caps fence height, often near 6 feet in front yards. A retaining wall holding back a slope or extra load requires a permit at any height.
Can a homeowner pull their own building permit in Washington?
Yes. You may pull the permit and do the work yourself on a home you own and occupy without being a registered contractor, under RCW 18.27.090. The exemption disappears if you build the improvement to sell, lease, or demolish, or if you hire helpers for pay, who must be Washington-registered contractors. Some cities also require you to sign an owner-builder acknowledgment form.
Sources we verified against
Every threshold on this page is anchored to Washington's building code or the sources listed above. Where a number varies by city and we could not verify it, we say "verify locally" rather than guess — a permit page you cannot trust is worse than no page at all.
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Permit or not, a licensed pro builds it to code the first time. Browse our verified directories — phone and website on every listing, and we never sell your info.
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