ADUs are allowed in Unincorporated WashingtonTypes:DetachedInternal
Types:DetachedInternal
Accessory Dwelling Unit (ADU) Rules for Unincorporated Washington, MD
Is your property eligible for an ADU?
# of Properties
33,378
Owner-occupied
86%
Zoning districts
39
Avg Home Value
$324,023
Median Lot Size
0.54 acres
Avg Income
$94,555
Residential Types:
33,378 housing units
Single Family
6%
Other
94%
Zoning Districts:
42,328 parcels · 39 districts
A(R
16%(6,762)
RS
15%(6,425)
RT
15%(6,360)
EC
15%(6,358)
Other
39%(16,423)
ADU Rules
What can you build in Unincorporated Washington, MD?
Unincorporated Washington, MD follows state and local rules for Accessory Dwelling Units. Here is a concise overview of the local rules.
Eligibility
- –Internal / Attached ADU: Conditional Use Permit
- –Detached ADU: Special Permit
Parking
- –ADU parking not listed in the schedule; unlisted uses determined by the Zoning Administrator based on the most similar listed use.
- –BZA may reduce required spaces if sufficient publicly available spaces exist within 500 feet.
- –General residential standards require 2 spaces per dwelling unit (single-/two-family and multi-family, with overflow).
ADU State Law
What can you build in Maryland?
- –Local-law mandate: By Oct 1, 2026, each legislative body must adopt a local law authorizing ADUs under this section.
- –Local zoning mostly remains: The subtitle generally does not alter local zoning power except as provided, but locals must establish policies that further the subtitle's intent.
- –Definition-based size cap: An ADU must be ≤ 75% of the size of the primary SF detached dwelling and subordinate in use; ADUs may be detached or attached.
- –Density/growth limits: ADUs must be excluded from density calculations and from measures limiting residential growth that pertain to the lot/parcel/tract.
- –Setbacks: Local law cannot set side/rear setbacks that exceed existing accessory-structure setbacks.
- –Parking: If a jurisdiction adds off-street parking requirements, it must consider specified factors and provide a waiver process, and must complete a parking study before adopting such requirements.
- –Alley access option: Local law may prohibit converting an accessory structure to an ADU if only vehicular access is from an alley.
- –Codes/adequate facilities: Local law must provide for ADU construction meeting public health/safety/welfare standards, including building codes and adequate public facilities provisions.
What's allowed on your lot?
These are the municipality-wide rules. What's allowed on a specific property also depends on state laws, setbacks, floor area ratio, lot coverage, environmental constraints, topography, and other property-specific factors. Search your address on FutureLot to see what's allowed on your property.
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ADU rules in other Maryland municipalities
Rules change at the town line. Check the municipality your property is actually in.
Washington County