Carroll

ADU Pass helps homeowners in Carroll — a USPS locale inside Baltimore, Baltimore city, Maryland — navigate the permit paperwork for building an accessory dwelling unit. This locale covers 1 ZIP code.

1 ZIP code

Baltimore City — county ADU rules and overlays

County ADU ordinance

Baltimore City is an independent city (city-county) under Maryland Constitution Article XI-A and is filed as a county-equivalent. There is no separate 'Baltimore City County' authority and no county board of supervisors; the Mayor and City Council exercise all powers that elsewhere split between a county and a municipality. ADU regulation is therefore a city-level matter under Article 32 (Zoning) of the Baltimore City Code, the post-2017 'TransForm Baltimore' rewrite. Accessory dwelling units (including conversion of historic rear carriage houses) are permitted across most residential districts subject to use-standard conditions in Title 14 (Use Regulations). There is no county-side ordinance distinct from the city ordinance because the city IS the county.

State-floor overlay: Maryland has no statewide ADU preemption; SB 382 (referenced in state task force work) establishes broader context for ADU authority on single-family-zoned parcels but does not override Baltimore City's local ordinance.

County regulatory overlays

Baltimore City administers several overlay systems that materially affect ADU project feasibility. The most pervasive is CHAP (Commission for Historical and Architectural Preservation) review, which covers 38 local historic districts and 200+ landmarks - including Mount Vernon, Fells Point, Federal Hill, and Roland Park - and requires design review for any exterior work. FEMA NFIP floodplain regulation applies citywide, with the regulated floodplain mapped on FIRMs adopted following FEMA's December 2018 preliminary maps. A substantial portion of southern and eastern Baltimore (every parcel within 1,000 feet of the Patapsco River shoreline and the harbor) falls inside the Chesapeake Bay Critical Area, triggering state-level stormwater and disturbance limits. There is no WUI fire zone in Baltimore City and no county-level coastal commission analogous to California's; the Critical Area Program is the Maryland equivalent.

CHAP Local Historic Districts and Landmarks — CHAP review is a hard prerequisite for DHCD permit issuance in mapped districts; budget 4-8 weeks for staff-level approval and longer for commission-level review on substantial alterations. Many of the most attractive carriage-house ADU conversion candidates fall inside CHAP districts.
FEMA NFIP Special Flood Hazard Areas (1% and 0.2% annual chance) — Floodplain elevation costs commonly add $20-50k to an ADU project in SFHA; lenders also require flood insurance on the structure.
Chesapeake Bay Critical Area (state program, city-administered) — Critical Area review is layered on top of normal zoning and (if applicable) CHAP review; budget separately for environmental staff turnaround.
BWI / Martin State Airport noise contours (limited city exposure) — Noise-zone exposure is not generally a permitting hard-stop for ADUs in Baltimore City and is included here for completeness rather than as a major project-feasibility factor.

Maryland state — ADU law and programs

State ADU law

Maryland enacted statewide ADU preemption with the Accessory Dwelling Units Act of 2025 — HB 1466 / SB 891 (cross-filed) — passed by the General Assembly in the 2025 Regular Session and effective 2025-10-01. Counties and municipalities with planning and zoning authority must adopt local laws compliant with the Act by 2026-10-01. The Act establishes that it is the policy of Maryland to promote and encourage ADU creation on land with a primary single-family detached dwelling. ADUs are defined as secondary units on the same lot/parcel/tract as a primary single-family detached dwelling, no greater than 75% of the size of the primary dwelling. Counties and municipalities cannot prohibit ADUs or impose unreasonable restrictions on their construction or rental. The 2025 ADU Act ALSO amends the Maryland HOA Act (Title 11B of the Real Property Article), prohibiting community associations from prohibiting or unreasonably restricting ADU construction and rental. The state has been preparing this framework since 2023 (SB 382 created the ADU Policy Task Force, which issued its final report 2024-05-31).

State HOA preemption

Maryland enacted HOA preemption for ADUs as part of the 2025 ADU Act. HB 1466 / SB 891 amended the Maryland Homeowners Association Act (Real Property Article, Title 11B), adding the ADU definition at §11B-101(a-1) and prohibiting HOAs from prohibiting or unreasonably restricting the construction or rental of ADUs on lots with primary single-family detached dwelling units. HOAs retain authority to (a) treat an ADU as a separate lot for voting and assessment purposes (optional, not required) and (b) impose reasonable design and architectural standards consistent with the community's overall character. The HOA preemption became effective 2025-10-01.

State financing programs

Maryland does not currently operate an ADU-specific statewide loan, grant, or forgivable-loan program tied to the 2025 ADU Act. The Maryland Department of Housing and Community Development (DHCD) administers a broad portfolio of homeownership, rental development, and home-repair financing — including the Maryland Mortgage Program, Settlement Downpayment Loan Program, Project Restore (commercial-to-residential conversions), and various Energy & Home Repair loan products. None target ADU construction directly, though Project Restore can fund ADU-like conversions, and the Energy & Home Repair Loan can fund ADU-related electrical, HVAC, and weatherization upgrades.

State housing programs

Maryland's primary state-level ADU program is the 2025 ADU Act framework: statewide preemption requiring local jurisdictions to adopt compliant ordinances by 2026-10-01, including HOA preemption. The Maryland Department of Planning maintains an ADU resource hub with technical assistance for local governments. Maryland does not currently operate a statewide pre-approved ADU plan catalog, an ADU rebate, or an impact-fee waiver statute, but the local-compliance window through 2026-10-01 is expected to produce additional ADU-specific incentive programs.

ADU Act 2025 Statewide Floor (HB 1466 / SB 891) — Counties and municipalities with planning/zoning authority must adopt compliant ordinances by 2026-10-01, allowing ADUs on every single-family-detached lot at up to 75% of primary dwelling size. Bars prohibitions and unreasonable restrictions. Includes HOA preemption.
Maryland Department of Planning ADU Resource Hub — Resource hub with model ordinances, FAQs for local governments (HB 1466 FAQ), task-force final report, and statewide ADU ordinance inventory.

Federal (United States) — ADU-relevant rules and programs

Federal ADU law

The United States has no federal statute that directly regulates accessory dwelling unit entitlement or design. Land-use authority over ADUs resides with states and local governments under the traditional police power. Federal engagement is limited to financing (Fannie/Freddie/FHA/VA/USDA), flood insurance (FEMA/NFIP), and discretionary housing programs (HUD), which are recorded in sibling sections of this file.

Federal financing programs

Federal housing-finance agencies and GSEs set nationwide underwriting rules that govern whether an ADU can be financed, appraised, and counted toward mortgage qualifying income. The relevant actors are Fannie Mae, Freddie Mac, FHA (HUD), VA, and USDA Rural Development.

Federal tax credits

There is no ADU-specific federal tax credit. ADUs may incidentally qualify for existing federal energy-efficiency and clean-energy tax credits when the ADU construction includes qualifying measures.

Federal housing programs

HUD administers several discretionary programs that can fund ADU-related activity at the grantee's election, but none is an ADU-specific program.

ZIP Code

21229

Post Office

340 S Loudon Ave, 21229