Hagerstown ADU Rules 2026: Proposed 75% Size, No Extra Parking & Alley Limits

Hagerstown has drafted one of Maryland’s clearest municipal ADU frameworks: one attached, internal or detached ADU up to 75% of the existing detached house, with no additional on-lot parking requirement. But the controlling document is proposal ZT-2026-02. As of September 16, 2026, we could verify Planning Commission review and an August 25 Mayor and Council work-session document, but not final adoption of the ADU package. Treat the standards below as proposed until the City confirms enactment and an effective date.

Jurisdiction comes first. A Hagerstown mailing address does not necessarily mean the property is inside the City’s corporate limits. City parcels follow the Hagerstown Land Management Code; properties outside the City generally follow Washington County zoning. Use the Maryland ADU Jurisdiction Finder before applying either guide.

Current-rule snapshot reviewed September 16, 2026. Proposed provisions are not treated as law. Confirm the ordinance number, adoption date and effective date with Hagerstown Planning and Economic Development before paying for plans. This guide is informational and is not legal, zoning, architectural, engineering or permitting advice.

Hagerstown’s proposed ADU rules at a glance

Which Hagerstown properties would qualify?

The proposal applies to properties in zoning districts where a single-family detached dwelling is permitted by right and where the lot already contains one such dwelling. It does not extend the ADU allowance to semidetached homes, existing two-family dwellings, townhouses or apartment buildings.

The draft also excludes nonconforming single-family homes in commercial or industrial districts that do not permit single-family or two-family dwellings. It contains a separate restriction for certain lots that do not front an improved public street. These details make an address-specific zoning check essential.

How large could a Hagerstown ADU be?

Proposal 2026-26 sets the maximum at 75% of the existing single-family detached dwelling’s floor area, whether the ADU is attached or detached. This mirrors Maryland’s HB 1466 definition.

The percentage is only the first ceiling. A detached unit would still need to fit the applicable accessory-building height, setbacks and cumulative accessory-building area. An addition would need to satisfy the standards for the main dwelling. Review the Maryland ADU size guide before assuming the full 75% is buildable.

Which ADU configurations would be allowed?

The proposed definition covers three configurations:

• Internal ADU: created within a modified existing detached house.
• Attached ADU: built as an addition to the primary detached dwelling.
• Detached ADU: located in a new or existing accessory structure.

This is broader than older “accessory apartment” models that only permit a unit within the house or limit it to a family member. The proposal is written to comply with the state requirement while, in the City’s words, going no further than required by statute.

How would setbacks work?

A new detached accessory building would need to meet the side and rear setbacks, height limit and cumulative accessory-building-area rules for its zoning district.

An existing accessory structure that does not meet today’s setbacks could potentially contain an ADU if the structure complied with the setbacks in force when it was built. That is not permission to assume an unpermitted shed or garage is legal; the building’s lawful status must be verified.

For an attached addition, the proposal generally applies the main house’s side and rear setbacks. If the existing house already encroaches into a current setback, the addition could follow that line only if it goes no farther into the setback and remains at least 3 feet from the property line for building-code purposes.

No extra parking—but an important alley-access restriction

The draft says an ADU applicant would not be required to provide additional on-lot parking. That is a meaningful homeowner benefit and avoids automatically paving more of a small city lot.

However, the same proposal bars an ADU in an accessory building when the only vehicular access to the new unit is by an alley. The site would need unobstructed driveway access from a public street to the accessory building. For Hagerstown’s alley-served garages and carriage structures, this may be the decisive feasibility issue.

Historic District Commission review may still apply

Proposal 2026-26 preserves Historic District Commission authority over building and site improvements in areas shown on the zoning map as subject to Commission review. A detached unit, visible addition, exterior stair, new openings or site changes may therefore need historic review even if the ADU use itself is allowed.

Treat historic status as an early design constraint. It can affect materials, massing, location and review timing.

What permits would a Hagerstown ADU need?

The proposal requires compliance with all City building, fire and housing codes and utility policies without waiver. Depending on the work, homeowners may need building, electrical, plumbing and mechanical permits, plus zoning and historic review.

Hagerstown provides online applications for building and trade permits through its Permits and Inspections Division. Before applying, ask Planning to confirm the parcel’s zoning, eligibility under the enacted ADU text and whether a site plan or Historic District Commission review is required.

Hagerstown City rules are separate from Washington County

Hagerstown is geographically within Washington County but administers its own zoning inside the City. Washington County’s ADU rules, including its separate 1,200-square-foot cap and other county standards, should not automatically be applied to a city parcel.

What Hagerstown homeowners should verify now

1. Confirm the property is inside Hagerstown.
2. Ask whether ZT-2026-02 has been adopted and is effective. Request the enacted ordinance or code text.
3. Confirm the lot contains one qualifying detached house in an eligible zoning district.
4. Calculate the 75% ceiling, then check the smaller practical limits.
5. For a detached unit, verify setbacks, height and cumulative accessory-building area.
6. Check driveway access from a public street. Do not assume an alley-only garage qualifies.
7. Check Historic District Commission jurisdiction.
8. Confirm building, trade, fire, housing and utility requirements before final design.

Primary sources used for this Hagerstown guide

• City of Hagerstown — 2026 Land Management Code amendment proposals
• City of Hagerstown — Land Management Code amendments page
• Mayor and Council — August 25, 2026 ZT-2026-02 work-session attachment
• Hagerstown Planning Commission — recommendation minutes
• City of Hagerstown — Permits and Inspections
• Maryland Department of Planning — HB 1466 ADU FAQ

Follow enactments and effective dates in the Maryland County & City ADU Rules Tracker. Maryland ADU Guide is maintained by Gijo John as an independent research publication.