Retaining wall permits, explained

Do you need a permit for a retaining wall?

The model rule fits in one sentence. The International Residential Code (IRC), Section R105.2, exempts from the building permit "retaining walls that are not over 4 feet in height measured from the bottom of the footing to the top of the wall, unless supporting a surcharge"^[1]. Two parts of that sentence decide most cases: where you measure from, and what the wall holds up.

Measure from the bottom of the footing

The 4 feet are not what you see above the lawn. They run from the bottom of the footing, below ground, to the top of the wall^[1]. Snohomish County, Washington, and Saint Paul, Minnesota, measure the same way^{[2] [4]}. A wall that shows 3 feet 6 inches above grade on a footing buried 8 inches is 4 feet 2 inches tall for the code, and needs a permit. In Saint Paul, the wall needs a permit if it is taller than 4 feet at any point^[4], so measure at the highest spot, not the average.

Ask what the wall holds up

A surcharge is any extra load on the soil behind the wall. Lake Stevens, Washington, defines it as any load in addition to level grade within the area defined by a 45-degree angle from the bottom of the footing to level grade^[5]. Snohomish County describes it as any additional load bearing on or against the wall, such as fill material, behind or above it^[2]. A sloping yard above the wall, a driveway, a parking pad, a shed or a house foundation can all be a surcharge.

When a wall supports a surcharge, the height exemption no longer applies. Eagle Mountain, Utah, requires a building permit for a surcharged wall regardless of its height^[3]; Snohomish County requires a permit and engineered plans for any wall of 4 feet or less that supports one^[2].

What counts as a retaining wall

More than block walls. Eagle Mountain includes any wall or similar system, stacked rocks and boulders included, intended to resist the lateral displacement of earth or other materials^[3]. A row of landscape boulders holding back a cut slope is a retaining wall there.

When you need an engineer

This is where retaining walls differ from fences and sheds: once a permit is needed, an engineer often is too.

• Snohomish County, Washington: engineered plans are required for any wall over 4 feet, and for any surcharged wall of 4 feet or less^[2].
• Saint Paul, Minnesota: three routes. Follow the block manufacturer's instructions (submitted with the application, and engineered if they say so), build exactly to the city's poured concrete or 8-inch block section details, or use a design by a structural engineer licensed in Minnesota. Any deviation from the city details requires an engineer, and the city lists height, tiered walls, soil types and surcharge loads from buildings as other reasons it may require one^[4].
• Eagle Mountain, Utah: the building plans must include all required engineering, and materials and installation must follow the current building code and the manufacturer's or engineer's specifications^[3].

What the city asks for

Saint Paul's list is a good model of a complete application^[4]:

1. Site plan: the lot, other buildings and structures, setbacks from property lines, and the linear feet of wall.
2. Manufacturer's instructions for the block system, if one is used.
3. Elevation view: changes in height, number of courses.
4. Section view: wall material, footing size and type, drainage behind the wall (drainage rock, drain tile, weep holes), any geogrid reinforcement, and the slope of the soil behind the wall.

Eagle Mountain asks for the owner and contractor details and the project valuation on the application, a site plan with lot dimensions, existing buildings and the distances from the wall to the property lines with slopes and grades defined, and building plans with dimensions, materials and engineering, all uploaded as PDFs^[3]. Lake Stevens adds that permitted walls often require a special inspections agreement to verify footings, drains and the final wall^[5].

Walls on the property line

A retaining wall on a boundary is a frequent trap. Saint Paul does not allow any part of a retaining wall on or over the property line unless a legal easement agreement has been recorded on all the properties involved with Ramsey County, and asks owners to have the agreement reviewed before recording it^[4]. Eagle Mountain says retaining walls are subject to setbacks^[3].

The inspections

A retaining wall permit is checked in the ground, not only on paper. Lake Stevens, Washington, says permitted walls often require a special inspections agreement to verify the footings, the drains and the final wall^[5]. Saint Paul's permit drawings must show the drainage behind the wall, the drain tile and weep holes, and any geogrid reinforcement^[4], which is what an inspector compares the trench against. Backfilling before the drainage is seen hides the part that keeps the wall standing.

What a retaining wall permit costs

Engineering, when required, is a separate cost paid to the engineer.

Building a wall without a permit

Skipping the permit has a cost of its own. In Wenatchee, Washington, work started without a required permit triggers a special investigation and a fee of $500 or triple the permit fee, whichever is greater, on top of the permit fee; the code adds that paying it does not make the work legal, and that work still illegal 90 days after a stop-work order is treated as a dangerous building and abated^[7].

Where we come in

For a wall that needs a permit, our permit team researches your city's threshold, how it measures height and what it counts as a surcharge, then prepares the site plan, the elevation and section drawings, the drainage details and the form, with the manufacturer's instructions attached, and tells you when an engineer's stamp is required. The All-in offer adds our review before you file and every round of city comments until the permit is issued.

Common questions