Who Reviews a Maryland ADU? Zoning, Building, Health and Utility Approvals Explained

One of the easiest ADU mistakes is asking a single office, “Can I build this?” and treating the answer as approval of the whole project. Maryland ADUs can involve several review tracks. Zoning can answer one question while building, Environmental Health or a utility answers another.

The exact offices vary by property. This guide explains the roles so you know what each answer does—and does not—establish.

1. Zoning or planning: Is this use and placement allowed?

The zoning/planning authority is usually the starting point for questions such as the applicable ADU framework, zoning district, setbacks, lot coverage, parking rules and other land-use standards. Maryland’s statewide ADU law sets requirements for local ADU laws, but local governments still administer zoning and related review.

First identify the correct authority with the Maryland ADU Jurisdiction Finder. A mailing city is not enough to establish who controls zoning.

2. Building department: Can the proposed construction meet applicable code?

Building review focuses on the construction or conversion itself. The submission may include floor plans, structural information, fire/life-safety details, energy-code information and other documents appropriate to the work. A basement conversion, garage conversion, addition and detached ADU can raise different building questions.

Maryland Land Use § 4-504 requires local ADU laws to provide for construction that meets public health, safety and welfare standards, including relevant building codes and adequate-public-facilities provisions.

See Maryland ADU Building Code: Fire Sprinklers, Separation & Egress, then confirm the current requirements with the reviewing building department.

3. Environmental Health: septic and private-well questions

If the property uses septic or a private well, the zoning desk may not be the office that can answer capacity or separation questions. Environmental Health or the local health department commonly handles those records and reviews.

For septic, obtain the approved design or bedroom rating before assuming an additional bedroom or dwelling can be served. A bedroom-count comparison can identify a reason to ask for review, but it does not certify capacity.

For a private well, ask whether the existing source, capacity and required separation distances can serve the proposed project. See the Maryland ADU Septic & Well Rules guide.

4. Public water and sewer utility: connection and capacity

A property already connected to public water or sewer is not automatically finished with utility review. Depending on the serving system and project, questions can include available capacity, connection configuration, meters, laterals and fees. Do not assume a separate meter or connection is either required or prohibited without checking the serving utility.

Maryland planning materials treat water/sewer availability and capacity as a distinct ADU implementation topic, and the statewide law preserves adequate-public-facilities review.

See Maryland ADU Utilities: Water, Sewer, Meters & Connection Fees.

5. Historic or environmental review: does an overlay add another step?

A property may also require review because of where it is located, not simply because it is an ADU. Examples include a historic district/property, Chesapeake or Atlantic Coastal Bays Critical Area, floodplain or another locally mapped environmental overlay.

Check the official parcel/map record rather than answering from memory. The Property Feasibility Checker treats an unknown overlay as something to verify instead of assuming “no.”

6. HOA or recorded private restrictions: a separate document check

Private restrictions are not the same as zoning. If an HOA, deed covenant or other recorded restriction applies, obtain the actual language. Maryland law limits unreasonable private restrictions on ADUs in covered circumstances, but short-term-rental restrictions and other details can require separate analysis.

See Maryland ADU HOA Rules.

What order should a homeowner use?

1. Jurisdiction: identify who reviews the address.
2. Zoning/planning: establish the applicable ADU path and major site standards.
3. Property constraints: resolve size, survey/placement, overlays and private restrictions.
4. Health/utilities: confirm septic, well or public-service questions that could change the design.
5. Building: prepare the code-compliant construction documents required for the selected concept.

The sequence can overlap, and a jurisdiction may organize review differently. The point is to avoid treating one office’s answer as universal approval.

Turn the office map into a permit file

Once you know which office answers each question, use the Maryland ADU Permit Checklist to gather the survey, size evidence, plans, utility records, overlay checks and other documents before you apply.

Use one project brief for every office

Bring the same core facts each time: property address and parcel number, primary-home type and size source, proposed ADU type and approximate size, survey/plat if available, water/wastewater type, and known overlays. That makes it easier to compare answers and identify which question is still unresolved.

Official Maryland sources

Maryland Land Use § 4-504 · MDP HB 1466 FAQ · MDP ADU Topics and Code Applicability

Reviewed September 25, 2026. Office names and review sequences vary by jurisdiction; confirm the current process for the property.