Maryland’s 2025 ADU law took effect October 1, 2025 and required local governments to authorize ADUs through local law by October 1, 2026. That deadline has passed. The next homeowner question is which ordinance and approval process now apply to the property, not whether the state automatically issued permission to build.
Does This Apply To My Project?
Maryland land with a primary single-family detached dwelling and a proposed secondary dwelling meeting the state ADU definition. Local implementation, building requirements and adequate public facilities provisions remain relevant.
What This Means For You
Maryland’s reform differs from an automatic statewide by-right approval rule. Planning guidance says a locality can use a conditional-use or special-exception process. Before paying for construction drawings, obtain the actual local ordinance and identify the approvals, site constraints and documentation your proposed unit will need.
Your Next Step
Ask the county or municipal planning office for its current ADU ordinance, adoption date and application route. Provide the primary dwelling type, proposed ADU size and existing water and wastewater arrangement.
Verify the Local Rule Is Actually in Place
The state implementation deadline does not establish that every jurisdiction completed its work or that every parcel qualifies. Ask for the ordinance number and current application instructions. If staff identify an unresolved implementation issue, obtain a written explanation of the process being used before assuming the missing local update removes all review requirements.
Check the Size and Approval Framework
The enacted definition limits the secondary unit to no more than 75 percent of the primary detached dwelling’s size and keeps it subordinate in use. Maryland Planning says local laws must authorize ADUs, but need not make them by right. Ask how floor area is measured and which locally adopted standards control the proposed design.
Separate Required Safeguards From Optional Policies
The law retains public-health, safety, building-code and adequate-public-facilities provisions. Planning guidance also describes parking-study and waiver requirements where local ADU parking obligations are established. Ask the local office to distinguish enacted requirements from recommendations in a model ordinance; a useful model is not necessarily the ordinance governing your parcel.
Common Questions
Does October 1, 2026 guarantee approval?
No. It was the deadline for local authorization laws. The property, proposed unit and application still need to meet the applicable rules, and local implementation must be checked.
Can I rely on an advertised 90-day approval guarantee?
Not on the basis of this act. The enacted document strikes out an earlier proposed 90-day ministerial-review provision. Use the adopted local process and ask for its actual review requirements.
Official Sources & Dates
Source announcement date: not stated by source. Effective date: 2025-10-01. Reviewed: 2026-10-18.
- Maryland Planning: Accessory Dwelling UnitsCurrent agency page distinguishes the October 1, 2025 effective date from the October 1, 2026 local-law deadline.
- Maryland Planning: HB 1466 Implementation FAQFull FAQ: 75-percent definition, local conditional-use/special-exception options, public facilities, parking study/waiver requirements and existing-ordinance review.
- Maryland Chapter 197 of 2025, HB 1466PDF page 3: retained 75-percent definition; page 5: local-law deadline and health/safety safeguards; pages 7–8: parking provisions and deleted 90-day proposal; page 12: October 1, 2025 effective date. Deleted bill language is not described as law.
Plan The Related Work
The authority responsible for your address determines applicability. This guide does not establish approval or replace professional advice.