Great News for Maryland Homeowners – Statewide ADU Law Clears the Way for Backyard Homes (SB 891)
New Maryland Law Open the Door For ADUs Across the State
Maryland just took a big step toward expanding flexible, more affordable housing. Senate Bill 891—now Chapter 196—establishes a statewide policy to promote and encourage Accessory Dwelling Units (ADUs) and requires counties and municipalities to authorize ADUs on lots with a single-family detached home as the primary dwelling. The law is approved and takes effect October 1, 2025; local governments must adopt their ADU ordinances by October 1, 2026.
What’s in the new ADU law?
A clear statewide policy. Maryland now affirms that encouraging ADUs on single-family detached lots is state policy to help meet housing needs. Local jurisdictions retain zoning authority but must set policies that further the intent of this law.
A definition homeowners can work with. An Accessory Dwelling Unit is a secondary home on the same lot as a primary single-family detached dwelling. It can be attached, created by converting space or an accessory structure, or built as a new detached unit. By statute, an ADU must be subordinate to the primary home and no larger than 75% of the primary home’s size.
Local governments must permit ADUs. By October 1, 2026, every county and municipality must pass a local law authorizing ADUs on land zoned for single-family residential use, and they may add safety standards (e.g., building code compliance). They may also bar conversions accessible only via an alley for safety reasons.
Parking: flexibility with guardrails. Local ordinances may set additional off-street parking requirements—but they must be grounded in objective factors (like construction cost of spaces, available curb length for on-street parking, stormwater impacts, and lot size variability) and include a waiver process. Before adopting those rules, localities must complete a parking study to understand needs and constraints.
HOAs and deed restrictions can’t “unreasonably” block ADUs. The law limits how private “restrictions on use” (like covenants, bylaws, or deed provisions) can be applied: they may not impose an unreasonable limitation on an owner’s ability to develop—or offer for rent—an ADU. (Historic properties are exempt from this section.) Separately, an HOA’s governing body may treat an ADU as a separate lot for voting and assessment purposes.
What the law doesn’t do
Earlier drafts considered statewide rules on ministerial permit timelines, impact fee caps, and utility connection fees. Those sections do not appear in the enacted chapter—the final law leaves those specifics to local codes and utility providers.
When does it take effect?
Earlier drafts considered statewide rules on ministerial permit timelines, impact fee caps, and utility connection fees. Those sections do not appear in the enacted chapter—the final law leaves those specifics to local codes and utility providers.
What this means if you own a single-family home in Maryland
A clearer path to a backyard home. Every jurisdiction will need an ADU authorization framework for single-family detached lots.
More predictability. The ADU definition and state policy set consistent baseline expectations, even as local details vary.
Private rules can’t be used to unreasonably stop you. HOA bylaws or deed restrictions can’t impose unreasonable ADU limits (historic properties aside), though HOAs may treat an ADU as a separate lot for voting and assessments.
Parking will be case-by-case, but waivers exist. Expect local rules tied to real-world constraints—with a required waiver process and parking study behind them.
Our take
This is a big win for homeowners and for Maryland’s housing supply. SB 891 creates a reliable on-ramp to ADUs statewide while giving local governments the flexibility to tailor details like parking and safety. If you’ve been on the fence about a backyard home for family, rental income, or aging-in-place, this new law makes the path forward clearer than ever.
