Montgomery County, MD Fence Regulations: Retaining Walls (2026)
Key Facts
- Permit threshold
- 36 in retained height (no surcharge)
- Engineering required
- over 48 in, or 36 in with surcharge
- Permit fee
- $180 (COMCOR 08.14.01 fee schedule)
- Design standard
- 1.5 safety factor against sliding/overturning
- Enforcement
- Dept. of Permitting Services; Class A violation
Summary
Montgomery County exempts residential retaining walls under 36 inches from permits, but any wall over 48 inches, or over 36 inches holding back a surcharge, needs an engineer-designed plan meeting a 1.5 safety factor under COMCOR 08.00.02.
Retaining walls over 48 inches (1219 mm) in retained height or over 36 inches (914 mm) in retained height that resist a surcharge, 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. 08.00.02.223 Section R405.1. Add to the title “exterior drainage system”. Delete the Exception. Add new subsection R405.1.2. Concrete or masonry foundation interior drainage system. Weep holes at least 2 inches (51 mm) in diameter, spaced at a maximum of 6 feet (1828 mm) on center must be installed in the footing or wall below the slab elevation connecting into the interior drains. Weep-hole inlets must have a minimum of 6 inches (153 mm) of gravel for the full perimeter of the foundation, extending at least 12 inches (306 mm) from the inlets and covered by a layer of approved filter membrane. 08.00.02.224 Section R405.1.1 Precast concrete foundation. Last sentence, replace words “into an approved sewer” with “by gravity or mechanical means into an approved drainage.” 08.00.02.225 Section R405.2.3 Drainage system. Last sentence, replace words “into an approved sewer” with “by gravity or mechanical means into an approved drainage.” 08.00.02.226 Section R406.1. Delete. 08.00.02.227
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: 2026 S-90: Montgomery County Code contains legislation effective through May 7, 2026 | Zoning Updated Effective: April 13, 2026 | COMCOR Regulations effective as of July 1, 2026).
Full Breakdown
Montgomery County's amendments to the residential building code exempt a retaining wall of 36 inches (914 mm) retained height or less from needing a permit, unless it resists a surcharge (sloped soil, vehicle loads, structure footings), crosses a lot line, sits in problem soils, or is part of a tiered system. Walls over 48 inches, or over 36 inches with a surcharge, must be engineered under Section R404.4 with a 1.5 safety factor against sliding and overturning. Department of Permitting Services fee: $180. Rockville, Gaithersburg, and Takoma Park enforce their own separate building codes and permits, not this county regulation.
Violations & Fines
Building or altering a retaining wall without a required permit or engineered design is a Class A violation: up to $1,000 criminal fine or a $500 civil penalty, $750 for a repeat offense.
Frequently Asked Questions
Do I need a permit for a retaining wall in Montgomery County, MD?
When does a Montgomery County retaining wall need an engineer's design?
Sources & Official References
Other rules in Montgomery County
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