State ADU law
Maryland ADU laws: every county must adopt an ADU law
Maryland’s 2025 law (SB 891 / HB 1466) took effect October 1, 2025 and gave local governments a year to comply.
What to do next: use this research to check your own lot and bids, then tell us about your project. Matching is not live yet, so we reply with information, not a quote.
Get ADU optionsWritten by HyreADU Research Desk Primary-source statute research
The short answer
Maryland ADU laws require every county and municipality with zoning power to adopt a local law allowing accessory dwelling units on single-family detached lots by October 1, 2026. Chapter 196 of the 2025 Laws of Maryland added Title 4, Subtitle 5 to the Land Use Article.
An ADU is defined as no more than 75% of the size of the main home. Local governments may not charge an impact fee or building excise tax on an ADU under 750 square feet.
Above that, the charge must be proportionate and cannot act as a de facto ban. Within 0.75 miles of a mass transit facility, the law limits new off-street parking requirements, with a local waiver process. The act took effect October 1, 2025.
What Maryland law requires of cities
Each row is from Chapter 196 (SB 891), 2025 Laws of Maryland, as enrolled and published by the Maryland General Assembly.
| Question | What the Maryland statute says | Citation |
|---|---|---|
| Must local governments allow ADUs? | Yes. Each legislative body must adopt a local law authorizing ADUs on land zoned for single-family detached homes on or before October 1, 2026. | Land Use Art. § 4-504(a) |
| What is an ADU? | A secondary dwelling on the same lot as a single-family detached home, no larger than 75% of its size, with its own sanitation, cooking, eating and sleeping. It can be inside the home, in or attached to an accessory structure, or a new detached building. | Land Use Art. § 4-501 |
| Lot size? | A local law may not require the lot to exceed the minimum size for the zone. | Land Use Art. § 4-504(d)(1) |
| Conversions? | Limits on setbacks are eased for ADUs converted from an existing accessory structure in the same footprint. | Land Use Art. § 4-504(d)(2)–(3) |
| Parking? | Near a mass transit facility (0.75 miles), no new off-street parking; elsewhere, no more than one space, unless the local law uses the listed factors. Any extra parking rule needs a waiver process. | Land Use Art. § 4-504(d)(4), (e) |
| Impact fees? | None under 750 square feet. At 750 or more, proportionate to the main home and not a de facto ban. Local waivers are allowed. | Land Use Art. § 4-506 |
| HOAs? | The act limits private restrictions that unreasonably limit ADUs and lets an HOA treat an ADU as a separate lot for assessments. | Ch. 196, Real Property Art. amendments |
Maryland ADU rules set by state law, as read on the official statute page on October 27, 2026.
Who the law covers and when it took effect
The duty applies to counties and municipalities with planning and zoning authority. The act was approved by the Governor on April 22, 2025 and took effect October 1, 2025. Local laws were due by October 1, 2026.
The enrolled bill text uses strike-through and inserts, so read the codified Land Use Article for exact wording. The Maryland Department of Planning publishes an FAQ for local governments on the same law (HB 1466).
What is still up to your city or county
Counties and cities keep wide discretion on design, square footage and standards, within the floors above. Each local law must set standards for size and design and exclude ADUs in some listed conditions.
Water and sewer utilities face limits on connection requirements. Ask your county for its adopted ADU law, since every jurisdiction’s version will differ.
How to check your own city
Answer these in order, in writing, before you pay for drawings.
- 1 Ask for your county’s or city’s adopted ADU law
It was due by October 1, 2026. Ask for the ordinance number and date.
- 2 Check the ADU size against the main home
The state definition caps it at 75% of the main home’s size.
- 3 Measure distance to transit
Within 0.75 miles of a mass transit facility, parking rules are limited.
- 4 Ask about impact fees and excise tax in writing
Under 750 square feet, none may be charged.
What this page does not cover
This page covers the Maryland statute only. It does not cover building codes, septic and well rules, HOA covenants, flood or wildfire overlays, or your city’s fee schedule. Those can still stop a project the statute allows.
We read the statute on October 27, 2026. Laws change, and courts read them.
If your project depends on one clause, have a land-use attorney or the planning department confirm it for your parcel.
For the national picture, see which states have ADU laws; for what to ask at the counter, see the ADU permit guide.
Questions
Does Maryland require counties to allow ADUs?
Are small ADUs exempt from impact fees in Maryland?
How big can an ADU be in Maryland?
When did Maryland’s ADU law take effect?
Written and audited by
HyreADU Research Desk
Primary-source research, data analysis and fact checking
We are a research desk, not a builder. We read the permit extract, the statute, the HCD return or the fee schedule ourselves, and publish each figure with its source and retrieval date.
Where a number cannot be traced to a primary source, we leave it out and say what we could not verify. Our store-based claims cover California only.
- CA
- the only state this desk will make store-based claims about
- 5
- jurisdictions with extracted ADU permit evidence
- 735
- CSLB-verified companies in the California store
- 0
- national claims from a one-state store
How this desk works
- Primary sources only. Permit counts come from the city or county that issued the permit. Production counts come from HCD’s Annual Progress Report. Rents come from HUD or the Census. We do not cite an article that cites a source; we download the source and compute the figure ourselves.
- This is a California site. The company store is 734 California firms and one New Mexico firm. Permit evidence exists for five named jurisdictions: Los Angeles, San Francisco, Sacramento, San José and unincorporated Marin. A number from that store is titled to those places, never to the United States.
- A permit is not a completion, and a license is not an ADU grade. California licenses no ADU classification. Being named on an ADU permit is evidence of engagement in that jurisdiction, not of quality, completion, or work anywhere else. Owner-builder permits are excluded from contractor counts.
- Calculation is labeled as calculation. Figures we derive are never presented as something HCD, HUD, the Census or a city published. Terner Center research is cited as Terner’s, never restated as ours.
- We do not design, permit or build ADUs, and we take no payment for placement, ranking or a favorable mention. Pages that look like rankings are not: they publish public-record counts and let the reader decide.
- Nothing here is legal, tax or financial advice. Zoning, underwriting and appraisal practice vary by jurisdiction, lender and appraiser. The useful next step on a specific lot is the planning counter and a licensed professional.
Data as of Land Use Art. §§ 4-501–4-507 (2025 Md. Laws Ch. 196) read on mgaleg.maryland.gov, retrieved 2026-10-27.. Authorship on this site is organizational: the analysis belongs to the desk rather than to a named individual, and we do not publish credentials we do not hold.
Our editorial policy sets out how we source, date and correct what we publish.
Sources & retrieval dates
- Chapter 196 (SB 891), 2025 Laws of Maryland, Land Use and Real Property, Accessory Dwelling Units , Maryland General Assembly, enrolled text Retrieved October 27, 2026.
Planning an ADU in Maryland?
Tell us about your lot and what you want to build. Matching is not live yet, so this is not a quote. We will send ADU options and the next questions to ask your city.
HyreADU is a publisher. It does not design, permit or build ADUs, and matching with builders is not live yet. This page describes state statutory text as published on the retrieval date.
It is not legal advice. Your city or county applies the rules to your lot, and its planning department is the authority for your parcel.