Do You Need a Permit for a Retaining Wall in Spokane? The 4-Foot Rule, Surcharges and When It Must Be Engineered (2026)

Short answer: in Spokane County and Spokane Valley, a retaining wall up to 4 feet tall, measured from the bottom of the footing to the top of the wall, usually doesn't need a building permit, as long as it isn't holding up a driveway, a path, a building or a slope. Inside the City of Spokane the rules are stricter. Here's how each jurisdiction words it, what "surcharge" means, and when the wall has to be engineered.

The 4-foot rule, and how it's measured

Washington adopts the International Residential Code (IRC) statewide. IRC Section R105.2 exempts from a building permit:

• Retaining walls not over 4 feet in height, measured from the bottom of the footing to the top of the wall
• Unless the wall supports a surcharge or impounds flammable or combustible liquids

The part people miss is the measurement. The 4 feet starts at the bottom of the footing, not at the lawn. A wall that shows 3 feet above grade with a buried footing and a course or two below ground can easily be over 4 feet by the code's measure.

Unincorporated Spokane County (Mead, Colbert, Chattaroy, Nine Mile and more)

Spokane County's permit exemption handout (BP-25) uses the same wording as the IRC: retaining walls not over 4 feet from the bottom of the footing to the top of the wall are exempt, unless supporting a surcharge or impounding Class I, II or IIIA liquids.

The County also reminds owners that exempt work still has to meet code and other County rules. An exempt wall can still need other approvals, for example if it's in a critical area or affects drainage onto a neighbor.

Spokane Valley

Spokane Valley builds under the same statewide IRC, so the same 4-foot, no-surcharge exemption is the starting point. Spokane Valley also regulates grading and land disturbance separately, so a wall that comes with a lot of cut or fill should be checked with the City's permit center before work starts.

City of Spokane: stricter than the 4-foot rule

The City of Spokane's guide sheet BUILD-08, Earth-Retaining Structures, starts from the other direction. It says a building permit and plan review are required for earth-retaining structures, the plans must carry the seal of a Washington-licensed professional, and a geotechnical analysis may be required. It then lists three exceptions:

• Reinforced concrete walls up to 3 feet above grade, with the foundation as deep below grade as the wall is tall above it, level backfill and no surcharge (parking areas, walkways or structural loads)
• Any earth-retaining structure up to 4 feet from the bottom of the footing to the top of the wall that sits at least 15 feet from property lines
• Modular block walls up to 4 feet from the bottom of the footing, built to the manufacturer's published guidelines, backfilled with clean gravel or crushed rock, carrying no surcharge, and limited to two terraces spaced at least twice the wall height apart, each terrace no more than 4 feet tall

So in the City, a 4-foot poured wall near your property line usually needs a permit even with nothing on top of it.

What counts as a "surcharge"

A surcharge is any extra load on or behind the wall beyond the flat soil it holds back. The City's BUILD-08 names these:

• Parking areas and driveways at the top of the wall
• Walkways and patios along its edge
• Structural loads, such as a building footing, fence or deck close behind it
• Sloping backfill, where the ground keeps rising behind the wall

In the County and Spokane Valley a wall carrying a surcharge loses the exemption, whatever its height. On sloped Spokane lots, where most walls exist to create a flat driveway, patio or shop pad, that's common.

When the wall must be engineered

Permits and engineering are separate questions. IRC Section R404.4, which Washington applies as written, requires a retaining wall to be designed to accepted engineering practice when it:

• Retains more than 48 inches of unbalanced fill (the difference in soil height from one side to the other) and isn't braced at the top, or
• Is over 24 inches tall and resists loads in addition to soil, like vehicles parked above it or a fence on top

That design has to check overturning, sliding, the pressure on the soil under the footing, and water uplift, with a safety factor of 1.5 against sliding and overturning. In the City of Spokane, permitted walls need plans sealed by a licensed professional in any case.

Drainage isn't optional

The code names water uplift for a reason. Water trapped behind a wall adds pressure pushing it out and reduces the friction holding its base in place. The City's modular block exception even requires clean gravel or crushed rock backfill. Every wall we build gets free-draining backfill and a way for water to get out, and in Spokane's freeze-thaw winters that matters even more for walls that hold wet soil.

Quick checklist before you build

• Find your jurisdiction: City of Spokane, Spokane Valley, another city, or unincorporated Spokane County
• Measure from the bottom of the footing, not from the grass
• Look at what's on top: a driveway, path, patio, fence, building or slope behind the wall changes the answer
• In the City, check the distance to the property line: under 15 feet changes the answer for a 4-foot wall
• Over 48 inches of unbalanced fill, or loads on top: plan on an engineered design
• Terraced walls: in the City, no more than two tiers, spaced at least twice the wall height apart
• When in doubt, call the permit desk before you dig

How Raven handles retaining walls

We build poured concrete and block retaining walls across the Spokane area, including the footing, drainage and backfill, and we tell you up front whether your wall falls under an exemption or needs a permit and an engineered design. See our Spokane retaining wall contractor page and our guide to choosing the right retaining wall. If the wall is for a driveway or shop pad, our permit guide for shops, pole barns and garages covers the building side.

Get a retaining wall quote

Call 509-350-2016 or request a free quote with the wall's length, rough height, what sits above it, and your address. We'll price it from your site and tell you which permits apply.

Sources

• City of Spokane BUILD-08, Earth-Retaining Structures
• Spokane County BP-25 Permit Exemptions
• 2021 International Residential Code, Chapter 1 (Section R105.2, work exempt from permit)
• WAC 51-51-003, Washington's adoption of the International Residential Code
• ICC Significant Changes, IRC Section R404.4 Retaining Walls
• City of Spokane Valley, Permit Center