ADU Rules in Bethesda, Maryland

Bethesda is an unincorporated community in Montgomery County, Maryland, directly bordering Washington DC's northwest side. There is no incorporated City of Bethesda — it is a Census-Designated Place, not a municipality. One of the most affluent communities in the United States, Bethesda is home to the National Institutes of Health (NIH), Walter Reed National Military Medical Center, and significant federal employment. All zoning and permitting is handled by Montgomery County.

CRITICAL: No City of Bethesda Government

Bethesda is NOT an incorporated city. All ADU permits, zoning questions, and inspections go through:

• Montgomery County Department of Permitting Services
• Montgomery County Planning Department

Montgomery County ADU Rules

Montgomery County's Zoning Ordinance governs ADUs in Bethesda. The county allows ADUs in residential zones to address housing affordability. Verify current ADU requirements with the Montgomery County Department of Permitting Services.

Permitted ADU Types

Per Montgomery County Zoning Ordinance (verify current standards):

• Accessory apartments (internal): Within primary structure
• Detached ADUs: Separate structure on the lot (carriage houses, backyard cottages)
• Garage conversions: Converting existing accessory structure

Verify current provisions with Montgomery County Planning.

Size Limits

Per Montgomery County (verify current standards):

• Maximum gross floor area
• Lot coverage restrictions

Setbacks

Per Montgomery County residential zone:

• Rear: Minimum setback
• Side: Minimum setback

NIH and Federal Campus Proximity

NIH and Walter Reed are federal campuses in Bethesda — they do not affect ADU rules on civilian residential properties, which use Montgomery County zoning.

Chesapeake Bay Watershed — Stormwater

Bethesda is in the Chesapeake Bay watershed. Montgomery County has stormwater management requirements that may apply to ADU construction.

Historic and Conservation Districts

Some Bethesda areas have historic designation or conservation overlay zones. Verify historic status with Montgomery County Historic Preservation Office.

Permit Process

1. Verify zoning: Montgomery County Department of Permitting Services
2. Stormwater/environmental review: If near waterways or with significant impervious area
3. Historic review: If in a historic or conservation district
4. Submit plans: Montgomery County Department of Permitting Services
5. Building permit and inspections
6. CO: Required before occupancy

Contact

Montgomery County Department of Permitting Services 2425 Reedie Drive, Wheaton, MD 20902 Phone: (240) 777-0311 Website: montgomerycountymd.gov/permittingservices

Disclaimer: There is no City of Bethesda — Montgomery County governs. ADU rules are evolving following Maryland's 2024 statewide legislation. Verify current standards with Montgomery County before starting any project.