If you own a single-family home in Anne Arundel County, a change is coming to what you’re allowed to build in your own backyard — and the clock is already running.

Anne Arundel ADU Deadline 2026: What Homeowners Should Know

Maryland passed the Accessory Dwelling Units Act of 2025, and it took effect October 1, 2025. The law requires every county in the state, including Anne Arundel, to adopt a local ordinance authorizing ADU development by October 1, 2026. Anne Arundel County already has a head start: Bill 6-23 previously removed the county’s old minimum lot-size requirement for ADUs, meaning many more properties are already eligible than before the state law even passed.

In plain terms: if you’ve ever thought about adding a basement apartment, an in-law suite, or a small backyard cottage to your property, this is one of the most favorable windows in years to actually do it.

What Counts as an ADU in Anne Arundel County

An Accessory Dwelling Unit — sometimes called a granny flat, in-law suite, or backyard cottage — is a second, self-contained living space on the same lot as your primary home. Anne Arundel County defines it as a second dwelling unit on an owner-occupied, single-family lot, capped at the lesser of 1,000 square feet or one-third of the primary home’s floor area. It can take a few forms:

• A converted basement with its own entrance, kitchen, and bathroom
• An attached addition connected to the main house
• A fully detached structure built elsewhere on the property

Why This Law Matters for Homeowners

A few reasons this is worth paying attention to now rather than waiting:

Housing for family, without losing privacy. An ADU gives aging parents or adult children their own space — steps away, not states away.

A real path to rental income. A legal, permitted ADU can generate long-term or short-term rental income, and in areas near Annapolis and the waterfront, that income potential is often stronger than in more inland parts of the county.

Added home value. A permitted second living unit is a tangible, usable asset — not just a renovation, but additional livable square footage with its own utility.

Early movers get ahead of the rush. As more homeowners become aware of this law over the next year, permitting offices and qualified local contractors will only get busier. Homeowners who start the conversation now are positioned to be first through the process, not waiting behind a backlog.

What Anne Arundel County Homeowners Should Do Now

1. Understand your property’s eligibility. Lot size, zoning, and setback rules still apply — Bill 6-23 removed the old minimum lot-size barrier, but every property is different.
2. Decide what kind of ADU fits your goals. A basement conversion, an addition, or a detached unit each come with different costs, timelines, and permitting paths.
3. Talk to a local contractor who already understands the county’s process. Not every ADU-focused company has deep local roots — look for a contractor who has actually worked in Anne Arundel County long-term and understands its inspection and permitting departments firsthand.

Madrid’s Contracting Is Tracking This Law Closely

We’ve spent over 35 years

 remodeling homes across Anne Arundel County — long before “ADU” was a common term. As the county finalizes its local ADU ordinance ahead of the October 2026 deadline, we’re staying on top of every update so our clients don’t have to track the legislative process themselves.

If you’re considering a basement conversion, in-law suite, or backyard cottage, now is a smart time to start the conversation — before the October 2026 deadline brings a wave of new interest countywide.