Maryland Engineering and Permit Requirements

The Maryland MBPS Residential Code 2015 states:

R404.4 Retaining Walls

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 Maryland.

Anne Arundel County requires a residential accessory structure building permit for retaining walls greater than 2-ft, and engineering for retaining walls greater than 4-ft. A building permit is required for commercial projects.

Baltimore County requires an additional data sheet and checklist signed by an engineer prior to receiving a permit, and an additional Certificate Letter of Compliance submitted to the building inspector when the wall is complete. DIY Retaining Wall will complete these documents. Residential owners are also required to sign an additional letter of acknowledgment.

Calvert County requires that any retaining wall greater than 3-ft be designed by a Maryland Professional Engineer.

Carroll County requires that any retaining wall greater than 4-ft be designed by a Maryland Professional Engineer.

Montgomery County has the most stringent requirements: any commercial retaining wall over 2-ft in height or supporting a surcharge requires a building permit. For residential retaining walls, any wall over 4-ft, supporting a surcharge (including slopes behind the wall), and all tiered walls systems require a building permit. In addition, walls over 7-ft require special inspections.

Prince George’s County requires building permits for retaining walls greater than 2-ft. Timber retaining walls are not allowed. All retaining walls require third-party inspection by a professional engineer.

The frost depth is 12″ in the state of Maryland. 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.