Somerset County ADU Rules 2026: 50% Size Cap, Owner Occupancy, Parking & HB 1466 Conflict

Somerset County already permits accessory dwelling units in several forms, but its current local rules are not fully aligned with Maryland’s 2026 ADU framework. The County zoning ordinance allows interior conversions, additions, stand-alone ADUs and additions to accessory buildings, while still requiring owner occupancy and limiting the ADU to 50% of the principal dwelling’s living area.

The safest way to plan in 2026 is to distinguish the currently published Somerset County zoning ordinance from Maryland’s newer HB 1466 requirements. I could not verify a later Somerset County ordinance that fully replaces the County’s existing 50% size rule as of September 13, 2026. Homeowners should therefore confirm the currently controlling standard with County Planning and Zoning before paying for final plans.

Last verified: September 13, 2026. This page is informational and does not replace a zoning determination, permit review, septic approval or legal advice.

Somerset County ADU status at a glance

What types of ADUs does Somerset County allow?

Section 5.10 of the County zoning ordinance is unusually clear about ADU forms. It allows an ADU to be created by converting existing living area, an attic or basement; adding floor area to an existing dwelling; constructing a stand-alone unit; or adding onto an existing accessory building such as a garage.

Only one ADU is allowed per lot under the current County rule. The ordinance also says an ADU may not be located on the same lot as a single-wide mobile or manufactured home.

The 50% size rule conflicts with Maryland’s 75% standard

Somerset County’s current ordinance limits the ADU to no more than 50% of the living area of the principal dwelling.

Maryland Department of Planning’s HB 1466 FAQ says local jurisdictions must authorize ADUs consistent with the state definition and may not limit qualifying ADUs below 75% of the size of the primary single-family detached dwelling. MDP recommends using finished living area above grade when measuring the primary dwelling, although the statute itself does not prescribe one measurement method.

Does Somerset County require owner occupancy?

Yes under the currently published ordinance. Section 5.10 says an ADU may be located on the same lot as an owner-occupied detached single-family dwelling.

HB 1466 does not establish one statewide owner-occupancy rule for every Maryland ADU, so this local condition should be treated separately from the size and parking compliance questions. Homeowners planning to rent both units should confirm whether the current owner-occupancy language remains enforceable for their proposed use.

How does Somerset County’s ADU parking rule work?

The current parking rule is conditional. If an ADU is created on a site with an existing house and adequate on-street parking, no additional ADU parking space is required.

One additional parking space located on or within 100 feet of the lot is required when the abutting roadways cannot accommodate on-street parking, or when the ADU is created at the same time as the principal dwelling.

Maryland’s HB 1466 framework says a jurisdiction that imposes additional ADU parking must first complete a parking study and must provide a waiver process. Because Somerset’s rule can require an additional space in some circumstances, homeowners should confirm how the County is administering the state-law requirement in 2026.

Critical Area, septic and utility capacity can control feasibility

Somerset County’s ADU section expressly directs properties in the Chesapeake Bay Critical Area to the County’s separate Critical Area Ordinance. That matters in a county with extensive shoreline, wetlands and environmentally sensitive land.

Properties using private septic and well systems should also treat wastewater capacity as an early feasibility check. Maryland’s HB 1466 guidance expressly preserves public-health, safety and adequate-facilities requirements, so state support for ADUs does not override septic limitations.

Use our Maryland ADU Septic & Well Guide before final design if the property is not served by public utilities.

Where does Somerset County currently allow ADUs?

The County use table lists ADUs as permitted by right in the Agricultural Residential (AR), Medium Density Residential (R-2), High Density Residential (R-3), Maritime Residential Commercial (MRC), Mixed-Use Village (C-1) and General Commercial (C-2) districts. It lists them as a special exception in the Conservation (CO) and Low Density Residential (R-1) districts.

The zoning district still matters even where the general ADU standards are satisfied, because underlying setbacks and other development standards apply when Section 5.10 does not provide a different rule.

Princess Anne and other incorporated areas need a separate authority check

Do not assume the Somerset County zoning ordinance controls every address in the county. The Town of Princess Anne administers its own planning, zoning and permit process and publishes a separate zoning code. Other incorporated municipalities may also have their own local authority.

If you are unsure which government controls the property, use the Maryland ADU Jurisdiction Finder before relying on County rules.

What Somerset County homeowners should verify before spending money

1. Confirm the controlling jurisdiction. Incorporated towns may administer their own zoning.
2. Confirm the zoning district. Some districts allow ADUs by right while CO and R-1 use a special-exception path.
3. Ask which size limit controls today. The County ordinance says 50%; Maryland guidance says compliant local laws may not cap below 75%.
4. Confirm owner-occupancy requirements. The current County ordinance requires the principal dwelling to be owner-occupied.
5. Check parking conditions. Determine whether on-street parking is considered adequate and whether a parking study/waiver process affects the parcel.
6. Check Critical Area status. Shoreline and sensitive-area rules may materially change the buildable envelope.
7. Check septic and well capacity early. Do this before paying for final architectural plans or a prefab deposit.
8. Re-check before October/after any new ordinance. Somerset still needs a clearly verified HB 1466-compliant local framework by October 1, 2026.

Primary sources used for this Somerset County guide

• Somerset County Zoning Ordinance — June 2025 amendments
• Somerset County Zoning Ordinance — 2025 use table
• Maryland Department of Planning — HB 1466 ADU FAQ
• Maryland Land Use Article § 4-504
• Town of Princess Anne — Planning, Zoning and Permits

For statewide comparison, use the Maryland County ADU Rules Tracker. Maryland ADU Guide is maintained by Gijo John as an independent research publication. Verify property-specific requirements with the controlling local agency before relying on this page for design, rental or construction decisions.