Height limits in Montgomery County, MD
Building codes decide when you need a permit; zoning decides how tall you can go. Both are below, measured the way Montgomery County measures them.
Rules last checked by a person on October 20, 2026. Guidance only; confirm with Montgomery County before you build.
Citywide
| ADU: Detached ADU height | The accessory-structure height limit (20 ft in R-60) |
|---|---|
| Fence: Maximum height | 6 ft 6 in |
R-60 Residential, one-family detached
| Shed: Height | 20 ft to the highest point |
|---|---|
| Garage: Height | 20 ft to the highest point |
R-90 Residential, one-family detached
| Shed: Height | 20 ft to the highest point |
|---|---|
| Garage: Height | 20 ft to the highest point |
Check your lot
Sources
- Montgomery County DPS, Building Permit Guidelines for Sheds in Residential Zones (rev. 7/14/2026). Checked 2026-10-19.
A building permit is required to install or construct any shed in Montgomery County... Regardless of its size, a shed must comply with the zoning ordinance for accessory structure setbacks and location.
- 44 CFR 59.1, definition of development (NFIP). Checked 2026-10-19.
Development means any man-made change to improved or unimproved real estate, including but not limited to buildings or other structures...
- 44 CFR 60.3, floodplain management criteria. Checked 2026-10-19.
Require permits for all proposed construction or other development in the community...
- 2024 IRC R105.2, Work exempt from permit (text published by the City of Benson, AZ). Checked 2026-10-19.
One-story detached accessory structures, provided that the floor area does not exceed 200 square feet. Fences not over 7 feet high. Decks not exceeding 200 square feet in area, that are not more than 30 inches above grade at any point, are not attached to a…
- Montgomery County DPS, Permits Required / No Permits Required (2024). Checked 2026-10-19.
Retaining walls not over 48 inches in height measured from the bottom of the footing to the top of the wall, unless supporting a surcharge.
- Montgomery County DPS, Guidelines for Building Residential Decks (rev. 04/15/2025). Checked 2026-10-19.
A building permit is required for all decks regardless of the height above grade.
- Montgomery County DPS, Guidelines for Accessory Dwelling Units (revised October 2026; reflects ZTA 26-06, Ordinance 20-36, effective October 5, 2026). Checked 2026-10-20.
An ADU may not be greater than 75% of the size of the primary single-family detached dwelling... [An ADU] must comply with the setback, height, and building lot coverage standards applicable to an accessory structure in the underlying zone... [Within one mi…
- Montgomery County DPS, R-60 Zone Development Standards (Sec. 4.4.9, guidance). Checked 2026-10-19.
Accessory Buildings: Rear yard only... 5 ft. Side setback... 5 ft. Rear setback, if not otherwise addressed... 20 ft. maximum height... footprint must not exceed 50% of the footprint of the main building or 600 sq/ft whichever is greater.
- Montgomery County DPS, Residential Fence Permit Process. Checked 2026-10-19.
A permit is required to install any type of fence in Montgomery County... The maximum permitted height of a fence or wall is 6' 6".