Maryland ADU permit requirements
Last reviewed: June 20, 2026
Quick answer
Permitting an accessory dwelling unit (ADU) in Maryland means pulling a building permit from the local authority that issues it. Maryland has a statewide ADU law that sets baseline standards local agencies must follow. ArchPermit tracks 14 source-cited requirements (11 required, the rest conditional) for this jurisdiction. These requirements were last reviewed June 20, 2026; confirm the exact forms and fees with the local permitting authority.
Maryland has a statewide ADU law. This baseline reflects that law plus the universal new-dwelling deliverables. Your local city or county still administers the permit and may add its own forms and fees, so confirm the exact checklist with them.
Maryland's HB 1466 (2025, Ch. 197, effective Oct 1, 2025) makes ADU encouragement state policy and requires localities with planning/zoning authority to adopt a local ADU-authorizing law by Oct 1, 2026. The Maryland Building Performance Standards (2021 codes) are the statewide minimum; confirm the local ordinance for site-specific rules.
- Adopted building code compliancerequired
The ADU must comply with Maryland's adopted residential building code: 2021 IRC (Maryland Building Performance Standards). Confirm the in-force edition with the local AHJ.
source · reviewed 2026-06-20 - Building cross-sectionsrequired
Cross-sections through the structure showing ceiling heights, wall/roof assemblies, insulation, and fire/sound-rated assemblies where required.
source · reviewed 2026-06-20 - Egress & life-safetyrequired
Emergency escape and rescue openings (egress windows), smoke and carbon-monoxide alarms, and required exits per the adopted residential code.
source · reviewed 2026-06-20 - Energy code compliancerequired
Energy-code compliance documentation for the conditioned space. Maryland: 2021 IECC (Maryland Building Performance Standards).
source · reviewed 2026-06-20 - Exterior elevationsrequired
Elevations of each affected building face showing height, exterior materials, and openings; existing vs. proposed where exterior changes occur.
source · reviewed 2026-06-20 - Floor plansrequired
Dimensioned floor plans of the ADU (and affected areas of the primary dwelling) showing rooms, uses, door/window locations, egress, and fixture/equipment locations.
source · reviewed 2026-06-20 - Foundation planrequired
Foundation plan with footing/stem-wall sizes and details (or a cited site-specific design), per the adopted residential code.
source · reviewed 2026-06-20 - Framing / structural plansrequired
Floor, wall, and roof framing showing member sizes, spans, spacing, connections, and lateral bracing; structural calculations where the framing is non-conventional.
source · reviewed 2026-06-20 - Local zoning / setback compliancerequiredverify locally
Compliance with the local jurisdiction's zoning: permitted use, setbacks, height, lot coverage, and any ADU-specific standards. These are set locally. Confirm with the permitting agency.
source · reviewed 2026-06-20 - Mechanical / plumbing / electricalrequired
HVAC, plumbing fixtures and lines, and electrical (panels, circuits, outlets, lighting, smoke/CO alarms) for the new unit.
source · reviewed 2026-06-20 - Site / plot plan (to scale)required
Scaled site plan showing property lines, setbacks, existing structures, the proposed ADU footprint with dimensions to property lines, driveways/parking, and utility locations.
source · reviewed 2026-06-20 - ADU ≤ 75% of primary dwellingconditionalverify locally
An ADU is a secondary unit on the same lot as a primary single-family detached dwelling, no greater than 75% of the primary dwelling's size.
source · reviewed 2026-06-20 - Local ADU-authorizing law required by Oct 1, 2026conditionalverify locally
Local governments with planning/zoning authority must adopt a law authorizing ADU development by Oct 1, 2026.
source · reviewed 2026-06-20 - No unreasonable deed/HOA limitsconditional
Deeds, HOA bylaws, and contracts may not impose unreasonable limitations on developing or renting an ADU.
source · reviewed 2026-06-20
Maryland ADU permit questions
- Do I need a permit to build an ADU in Maryland?
- Yes. An accessory dwelling unit (ADU) in Maryland requires a building permit, and Maryland has a statewide ADU law that sets baseline standards local agencies must follow. ArchPermit tracks 14 cited requirements for this jurisdiction (11 required, the rest conditional). Always confirm the exact forms, fees, and code edition with the local permitting authority that issues the permit.
- What does an ADU permit package require in Maryland?
- Core required items include: Adopted building code compliance; Building cross-sections; Egress & life-safety; Energy code compliance; Exterior elevations; Floor plans, plus 5 more. Each requirement links to its authoritative source, and nothing is permit-ready until an independent licensed professional reviews and seals it.