ADUs are allowed in Unincorporated CarrollTypes:DetachedInternal
Types:DetachedInternal
Accessory Dwelling Unit (ADU) Rules for Unincorporated Carroll, MD
Is your property eligible for an ADU?
# of Properties
42,600
Owner-occupied
87%
Zoning districts
30
Avg Home Value
$432,231
Median Lot Size
0.97 acres
Avg Income
$131,850
Residential Types:
42,600 housing units
Other
100%
Zoning Districts:
55,746 parcels · 30 districts
A
38%(21,131)
R-20000
17%(9,609)
R-40000
17%(9,295)
C
13%(7,346)
Other
15%(8,365)
ADU Rules
What can you build in Unincorporated Carroll, MD?
Unincorporated Carroll, MD follows state and local rules for Accessory Dwelling Units. Here is a concise overview of the local rules.
Eligibility
- –Internal / Attached ADU: By Right
- –Detached ADU: By Right
Interior / Attached ADU Size Limits
- –Maximum size: Residential districts cap is the greater of 800 sq ft or one-third of the principal dwelling’s livable floor area; Agricultural and Conservation districts cap is 1,000 sq ft.
Detached ADU Size Limits
- –Maximum size of 1,000 sq ft in Agricultural and Conservation districts; no size limit in Residential districts.
Max Units
- –Residential (R-40k/20k/10k/7.5k): 1 ADU total/lot (attached or detached); attached: 1 per principal dwelling unit.
- –Agricultural (A) & Conservation (C): 1 ADU total/lot (attached or detached).
Owner Occupancy
- –Property owner must occupy either the principal dwelling or ADU
Parking
- –Residential districts: 2 off-street spaces per ADU (attached or detached); Agricultural/Conservation districts: 1 additional off-street space per ADU bedroom; no maximum; only 1 ADU per lot; attached ADU parking is in addition to principal-dwelling parking.
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.
Carroll County