Baltimore County, MD Fence Regulations: Retaining Walls (2026)

Section 33-5-105(c) of the County Code governs when a retaining wall is mandatory rather than optional. If a lot is graded so its new surface is lower than the adjoining property, the new grade must meet the existing grade at the property line at a slope no steeper than one foot vertical to three feet horizontal unless the county approves a different angle; if that slope cannot be achieved within the lot, a retaining wall must be built entirely on the land of the owner causing the grading, and it cannot encroach onto the neighbor's property.

The same rule runs in reverse for fill: when a residential lot is raised above the adjoining grade, the fill must slope down at an angle flatter than the material's angle of repose and no steeper than 1:3, and if the toe of that slope, even combined with a storm drain or swale running to an approved outlet, would cross the property line, the owner making the fill must build the retaining wall on their own land instead. Land not used for residential purposes gets a steeper allowance of 1 foot vertical to 2 feet horizontal for cut-and-fill slopes.

Beyond the wall itself, Section 33-5-105(g) requires that any excavation made at or close to a property line, public right-of-way, or public property have its sides and banks properly supported according to plans the county approves, and the Department of Permits, Approvals and Inspections or Public Works and Transportation can order the owner to add walls, fences, or guardrails if the excavation poses a public safety hazard. Retaining walls holding fill in a mapped flood hazard area also fall under Section 32-8-507(b), which requires flood damage-resistant construction and anchoring against flotation for that structure.