Maryland Accessory Dwelling Units Act of 2025 (HB 1466): what it allows on a lot
Accessory Dwelling Units Act of 2025 (HB 1466) is Maryland law, and the official source is at planning.maryland.gov.
In force October 1, 2025. Every county and municipality must adopt, by October 1, 2026, a law that allows an accessory dwelling (up to 75 percent of the house's size) on land with a single family detached home. HB 1538 (2026), which would add one internal and one external unit by right, had a House hearing March 13, 2026 and is not law.
Whether it applies to one lot turns on where the lot is and what it is zoned; the city, county or state office named in the law decides. Mapped areas are approximate. This is a plain reading of public law with its source, not legal advice.
Free, no account. ParcelSheet shows the lot's mapped size, parcel lines and flood zone, and this law on the lot's Maryland sheet.
Other Maryland laws on a lot: Critical Area.