Maryland is betting on “granny flats” to loosen a painfully tight housing market, nudging homeowners to think about tucking extra homes into their backyards and basements. A new statewide accessory dwelling unit law that kicked in for 2025 puts every county and Baltimore City on the hook to write local ADU rules, all under a hard deadline of Oct. 1, 2026. Builders and homeowners say ADUs can help, but price tags, permits, and HOA fine print still sit between the law on paper and real units in real yards.
What the law requires
Per the Maryland Department of Planning, House Bill 1466 took effect Oct. 1, 2025, and orders local jurisdictions to adopt ADU ordinances by Oct. 1, 2026. The law defines an ADU as a secondary dwelling that is no larger than 75% of the primary home and that has permanent provisions for sanitation, cooking, eating, and sleeping in order to count as a full dwelling unit. Local governments can layer on objective design and safety standards, but the state text blocks rules that would function as a practical ban on ADUs.
Costs and the homeowner calculus
Builders say these are not weekend projects. Makara Builders estimates that backyard cottages typically run between $150,000 and $350,000 and can be finished in roughly three to four months once permits are in hand. One homeowner in Silver Spring told The Baltimore Banner he spent about $255,000 to convert a garage into a 380-square-foot ADU and now rents it for roughly $1,400 a month. That tradeoff, a major up-front cost for a steady but modest rental stream, helps explain why some owners have taken the plunge while ADUs have not yet scaled across the state.
Local rollout and legal limits
Some jurisdictions are already rewriting the rulebook. Howard County moved this winter to allow detached ADUs in more zones as part of CB3-2026, a zoning change the council approved and the county executive signed. At the same time, House Bill 1466 tries to clear one of the most common roadblocks by saying deed restrictions and HOA covenants cannot unreasonably block ADU construction, while still allowing HOAs to treat ADUs as separate lots for voting and assessments. County planners say the unglamorous details, such as technical assistance, parking, and utility hookups, will determine how many backyards actually turn into new homes.
Will ADUs move the needle?
Policy makers and housing experts caution that ADUs are a tool, not a miracle fix. The Maryland Department of Planning ADU Task Force noted a statewide housing shortfall of nearly 96,000 units and recommended ADUs as one piece of a broader strategy. As architect Eric Saul told The Baltimore Banner, “They thought everybody was going to build one, tomorrow,” and although fears about neighborhood disruption have not played out, ADUs “haven’t been nearly as disruptive” and have not yet made much of a dent in the shortage.
As counties hustle to get rules on the books before Oct. 1, the day-to-day obstacles, such as permitting timelines, utility capacity, parking standards, and financing, will decide whether granny flats stay a niche option or quietly add a stream of new homes. State planners and local officials say they will publish guidance and technical assistance in the coming months to help turn the statute into actual roofs and doors on the ground.
