Maryland ADU Law
Maryland ADU Law: SB 891, HB 1466 & Anne Arundel's Bill 6-23
A plain-language guide to the state and county rules that govern accessory dwelling units in Anne Arundel County — and what they mean if you’re planning to build one.
Two separate laws now govern ADUs if you’re building in Anne Arundel County: a statewide Maryland law and a county-level ordinance that actually came first. Knowing how they fit together — and which one sets the rule for your specific project — is the difference between a smooth permit process and an expensive surprise.
Maryland's Statewide ADU Act (SB 891 / HB 1466)
Effective October 1, 2025, Maryland’s ADU Act requires counties and municipalities to allow accessory dwelling units by right on lots zoned for single-family residential use — meaning a local government can no longer flatly ban ADUs or require a discretionary special-exception hearing just to build one. Counties can still apply reasonable standards (size caps, setbacks, parking, owner-occupancy in some cases), but they can no longer say no outright. The law was designed to open up a lower-cost path to housing supply and to let homeowners generate rental income or house family members without a rezoning fight.
Anne Arundel County's Local Ordinance (Bill 6-23)
Anne Arundel County was ahead of the state on this: Bill 6-23 established the county’s own ADU permitting framework in 2023, two years before Maryland’s statewide law took effect. That means the county already has a working local process for detached ADUs, attached additions, and conversions of existing space (garages, attics, basements) — including its own standards for size, setbacks, and parking. Where the state law sets the floor every county must meet, Bill 6-23 is the specific local rulebook that actually processes your permit application.
What This Means If You're Building an ADU
- A permit is still required. “By right” means the county can’t reject the concept — it doesn’t mean permitting is skipped.
- Local standards still apply. Setbacks, height limits, size caps, and parking requirements are set at the county level under Bill 6-23, not the state law.
- Owner-occupancy and rental rules can vary. Some jurisdictions require the main house or the ADU to be owner-occupied; confirm current requirements before assuming you can rent both units freely.
- Existing local ordinances stay in force. Anne Arundel’s Bill 6-23 predates the state act and continues to govern the day-to-day permitting process here.
What Will Your Compliant ADU Actually Cost?
Permitting is only one piece of the budget. For a full breakdown by ADU type — detached, garage conversion, attic conversion, basement conversion, and in-law suite — see our Maryland ADU cost guide.
Maryland ADU Law Questions
What is Maryland's ADU Act (SB 891 / HB 1466)?
It’s a statewide law, effective October 1, 2025, requiring counties to allow accessory dwelling units by right on single-family-zoned lots, subject to reasonable local standards. It replaces outright bans and discretionary approval hearings with a defined permitting path.
Do I still need a permit under the new state law?
Yes. The state law guarantees your right to apply and be considered — it doesn’t remove the permit requirement. In Anne Arundel County, that permit is processed under Bill 6-23.
Does Anne Arundel County have its own ADU rules?
Yes — Bill 6-23, passed in 2023, is the county’s dedicated ADU ordinance and predates Maryland’s statewide law by two years. It sets the local standards (setbacks, size, parking) your project has to meet.
Let Us Navigate the Permitting for You
We handle design, permitting, and construction start to finish for ADU projects across Annapolis, Glen Burnie, Pasadena, Severna Park, Crofton, and Odenton — navigating both the state ADU Act and Anne Arundel’s Bill 6-23 for you.