Do I Need a Permit to Build a Retaining Wall in Wisconsin?

The permit threshold for retaining walls in Wisconsin is typically 4 feet in height, measured from the bottom of the footing to the top of the wall. This is the most common standard across municipalities, though some cities measure from grade level to the top. Retaining walls at or below 4 feet generally do not require a building permit, but they must still comply with zoning setback requirements. Once the wall exceeds 4 feet, a building permit is required and most municipalities also require structural engineering drawings stamped by a licensed Professional Engineer (PE). The engineering requirement exists because taller retaining walls must resist significant lateral soil pressure, and failure can cause property damage, injury, or death. An engineered retaining wall design specifies the wall type (gravity, cantilever, segmental, soldier pile), footing dimensions, reinforcement details, drainage behind the wall, and soil bearing capacity requirements. Engineering costs for a retaining wall design typically range from $500 to $2,500 depending on the complexity. Permit fees for engineered retaining walls range from $150 to $1,000. Drainage is the most common cause of retaining wall failure and a key focus of both the engineering design and the building inspection. Every retaining wall must have adequate drainage behind it — typically a gravel backfill with a perforated drain pipe at the base that routes water away from the wall. Without proper drainage, hydrostatic pressure builds behind the wall and can cause it to bow, crack, or collapse. The building inspector will check drainage provisions at the rough inspection before backfill is placed. Special considerations apply in certain situations. Retaining walls within the public right-of-way require a right-of-way permit. Retaining walls near property lines may require a survey to confirm the wall does not encroach on neighboring property. In flood zones or areas with high water tables, additional engineering requirements apply. If you are building multiple terraced walls to stay under the 4-foot threshold, be aware that many municipalities measure the total retained height — two 3-foot walls close together may be treated as a single 6-foot wall and require a permit and engineering.

Check Your Municipality

Permit requirements, fees, and exemptions vary by municipality. Verify the specifics for your location.