A second home on your lot, done by the rules of your county
Seven Maryland counties now allow accessory dwelling units, each with its own bill, size cap and permit path. We lay out the rule for your county and connect you with a licensed Maryland builder who already does this work.
Who this is for
A parent moving closer, an adult kid who needs a door of their own, a rental that pays the mortgage, or an office that is not the kitchen table.
What we do
We read the county bills, keep the rules current, and match you with a licensed builder. The builder designs, permits and builds the unit. We never claim to.
What it costs you
Published Maryland ranges by unit type, county permit fees, and the sprinkler number, each with its source named on the page. No made up averages.
The rule where you live
Every Maryland county had to adopt a local ADU law by October 1, 2026. Some did years ago, some are still voting. Tap your county for the bill, the size cap, the permits and the cost.
Three steps, one builder
- 1
Send the address and the kind of unit
Backyard cottage, attached suite, basement or garage. Well or public water. That is all we need to start.
- 2
We check the county rule
Size cap, bedrooms, owner occupancy, and whether the unit needs a fire sprinkler system. You get a straight answer before anyone quotes.
- 3
A licensed builder calls you
One Maryland home builder who already does ADUs in your county walks the lot and gives you the price. No bidding war, no list of strangers.
A detached ADU gets a sprinkler system in every Maryland county
Under the state building code a backyard cottage is a new dwelling and gets an NFPA 13D system; a basement or attached unit inside an unsprinklered house usually does not. Our sister company, Maryland Fire Sprinklers, designs and installs them, so the answer is on the table before the builder quotes.
Maryland ADU questions, answered
- Which Maryland counties allow accessory dwelling units?
- Seven counties have an ADU rule we track: Anne Arundel, Howard, Baltimore County, Montgomery, Prince George's, Frederick and Charles. Each has its own bill, size cap and permit path, and the state law (Chapter 196 of 2025) sits underneath all of them.
- How much does an ADU cost in Maryland?
- Published ranges run about $120,000 to $300,000 and up for a detached unit, $100,000 to $250,000 attached, $80,000 to $200,000 for a basement and $75,000 to $150,000 for a garage conversion, before county fees and the sprinkler line.
- Does a Maryland ADU need fire sprinklers?
- A detached ADU is a new dwelling and gets an NFPA 13D sprinkler system in every Maryland county. A basement or attached unit inside an unsprinklered house usually does not.
- Do you build the ADU yourselves?
- No. We are a referral service. We check the county rule for your lot and connect you with a licensed Maryland home builder who already builds ADUs in that county.
Tell us about the lot
Address, county and the kind of unit. We answer with the rule that applies and the name of a licensed builder who works there.