Iowa Engineering and Permit Requirements

Section R404.4 of the Iowa Residential Code 2015 (IRC 2015) states:

Retaining walls that are not laterally supported at the top and that retain in excess of 48 inches (1219 mm) of unbalanced fill, or retaining walls exceeding 24 inches (610 mm) in height that resist lateral loads in addition to soil, shall be designed in accordance with accepted engineering practice to ensure stability against overturning, sliding, excessive foundation pressure and water uplift. Retaining walls shall be designed for a safety factor of 1.5 against lateral sliding and overturning. This section shall not apply to foundation walls supporting buildings.

Any wall over 4-ft or any wall over 2-ft supporting a surcharge requires engineering. DIY Retaining Wall provides engineering services in Iowa.

The frost depth is 12″ in the state of Iowa. Concrete walls with a poured concrete footing must extend to the frost depth, while SRW walls do not need embedment that exceeds the frost depth.

Note, some cities, like Pleasant Hill, require permits for all retaining walls, regardless of height or surcharge. It is important to check your city/county building codes.