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New Maryland Legislation: Accessory Dwelling Units (aka Small Houses) Act of 2025

Posted July 15, 2025 at 7:08 AM

Land Development, Maryland Property Tax News, News & Events, Real Estate

The Maryland General Assembly has passed new legislation, specifically Senate Bill 891 and House Bill 1466, collectively known as the Accessory Dwelling Units Act of 2025, to promote and encourage the creation of Accessory Dwelling Units (ADUs) on properties zoned for single-family homes. This legislation aims to increase housing availability and affordability by allowing homeowners to add a secondary dwelling unit to their property. Key provisions include a statewide policy framework, prohibiting unreasonable restrictions, and adjusting homeowners’ association rules to accommodate ADUs. 

The bill will take effect on October 1, 2025, and applies to charter counties and Baltimore City, with the goal of increasing housing options and affordability across Maryland. By October 1, 2026, local legislative bodies must adopt laws authorizing ADU development, which are defined as secondary dwelling units (aka Small Houses) that are on the same lot as a primary single-family dwelling and not larger than 75% of the primary unit’s size. The bill requires local jurisdictions to create policies that facilitate ADU development while ensuring public health, safety, and welfare standards are met. The legislation aims to address housing needs by making it easier for homeowners to create additional living spaces on their properties, such as converting existing structures or building new, smaller units.

What is an Accessory Dwelling Unit (ADU)?
An ADU is a secondary housing unit (aka Small House) situated within a single-family residential plot, providing an opportunity to make the most of Maryland’s existing residential spaces. These come in various forms, each with their unique attributes and suitability:

  • Detached ADU: A standalone structure, offering complete independence from the main residence.
  • Attached ADU: Shares at least one wall with the primary house, ideal for easy accessibility while still providing some separation.
  • Garage or Basement Conversion ADU: Reinvents an existing garage or basement space into a functional and cozy living area.

As stipulated by the current ADU requirements in Maryland, these units generally require a straightforward ADU permitting in Maryland process, benefiting homeowners with a relatively smooth journey from conception to completion.

Click here for Montgomery County ADU zoning and permitting guidelines.

Click here for Rockville City ADU zoning and building requirements.

The Purpose and Benefits of ADUs
Why are more Marylanders jumping on the ADU bandwagon? The benefits are clear and far-reaching:

  • Adding an ADU can significantly increase property value, making it an attractive feature for future home buyers.
  • They provide a buffer for recent college graduates, enabling young adults to save and plan their next move in the comfort of a family-owned ADU.
  • For those who love to entertain or have extended family stay over, ADUs offer a private and comfortable space for guests.
  • They serve as a sanctuary for aging parents who desire proximity to their loved ones while maintaining their independence.
  • Homeowners can leverage ADUs as a source of passive income through renting, offering a solid investment opportunity.

How MM&C Land Use and Zoning Attorneys Can Help
Sean Hughes is an attorney in Miller, Miller & Canby’s Land Use practice group. His career spans more than three decades of focus in land use, zoning and wireless telecommunications. The firm’s Land Use & Development practice concentrates on land use, zoning, subdivision and planning law in Montgomery County and the municipalities within the county. Our areas of expertise include zoning, special exceptions, conditional uses, building variances, sign variances, subdivision, master planning, building permit issuance, and administrative and real estate matters related to land development. Learn more about Miller, Miller & Canby’s Land Use and Zoning practice by clicking here or contact us at 301.762.5212.

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