Last researched: September 18, 2026. Centreville is actively rewriting its ADU rules. This is not a generic Queen Anne’s County page: the Town has its own zoning code and Planning Commission, and its 2026 records contain a detailed draft §170-39.1 covering size, owner occupancy, parking, detached units, density and Critical Area treatment.
Quick homeowner answer: Centreville already added an ADU definition to its code in 2025, but the Town’s 2026 Planning Commission has been developing a broader ADU ordinance to comply with Maryland law. The July 15 draft would allow one ADU on a lot with a single-family detached home, cap it at 75% of the primary dwelling, allow the owner to live in either unit, require one parking space with an administrative waiver, and apply accessory-building rules to detached ADUs. Because the material we verified is a draft Planning Commission ordinance, confirm enactment before treating those provisions as final law.
Centreville ADU status at a glance
| Question | What we verified |
|---|---|
| Separate from Queen Anne’s County? | Yes. Centreville has its own Chapter 170 zoning code and Planning Commission. |
| ADU already defined? | Yes. Ordinance 12-2025 added an ADU definition for an attached or detached extension to an existing single-family structure. |
| 2026 ordinance status | Planning Commission work sessions reviewed a draft new §170-39.1. July 15 packet contains detailed proposed standards; verify Town Council enactment before relying on them as final. |
| Proposed number | One ADU per lot with a single-family detached dwelling. |
| Proposed maximum size | 75% of the primary dwelling’s gross floor area. |
| Proposed owner occupancy | Owner would occupy either the primary dwelling or the ADU. |
| Proposed parking | One off-street space, with waiver authority for the Zoning Administrator. |
| Detached ADU | Proposed to follow accessory-building standards in addition to ADU rules. |
| Critical Area | Draft says applicable Critical Area Overlay requirements also apply, with the more restrictive/stringent provision controlling if inconsistent. |
1. Centreville is not the same zoning jurisdiction as Queen Anne’s County
Do not take the County’s 1,500-square-foot ADU framework and apply it automatically to an address inside Centreville. The Town maintains its own Chapter 170 zoning code. For property outside Town limits, use our Queen Anne’s County ADU guide; for an in-Town parcel, Centreville’s rules control the municipal zoning analysis.
2. Centreville started changing its ADU code before the 2026 deadline
The Town code already contains an ADU definition added September 18, 2025 by Ordinance 12-2025. It describes an ADU as a separate, complete housekeeping unit with a separate entrance, kitchen, sleeping area and full bathroom facilities, as an attached or detached extension to an existing single-family structure.
In January and March 2026, the Planning Commission began a more comprehensive review using Maryland’s ADU compliance materials. By July, the Commission was reviewing a draft ordinance and related changes to residential zoning districts, use tables, parking, buffer yards, CBD and TND provisions.
3. Proposed size rule: 75%—and the draft explains how to measure it
The July 15 Planning Commission packet proposes that an ADU may not exceed 75% of the gross floor area of the primary dwelling. The draft is unusually useful because it also addresses measurement: primary-dwelling area would be based on State Department of Assessments and Taxation records, while ADU area would use finished habitable area.
That measurement detail matters. A homeowner should not simply multiply a real-estate listing’s advertised square footage by 0.75 and assume that is the permit number. Ask the Zoning Administrator which source and spaces count under the finally enacted ordinance.
You can use our Maryland 75% ADU Size Calculator for an initial estimate.
4. Detached ADUs still have to fit Centreville’s accessory-building rules
The draft §170-39.1 would subject detached ADUs to the Town’s accessory-building standards. Centreville’s 2026 work packets also illustrate how rear-yard footprint limits, lot coverage, height and setbacks can constrain an accessory structure even when the ADU use itself is allowed.
One example used by the Town shows how a required rear yard and the rule limiting accessory-building footprint to a percentage of that rear-yard area can become the real bottleneck. This is why “75% size allowed” does not mean “75% will physically fit.”
5. Proposed parking: one space, but with a waiver path
The July draft proposes one off-street parking space for the ADU, while allowing the Zoning Administrator to waive that requirement under the ordinance’s waiver framework. Maryland’s HB 1466 places conditions on additional local ADU parking mandates, so the waiver and Town parking analysis matter.
If parking is the only reason your lot appears infeasible, ask about the current waiver standard before redesigning the property.
6. Owner occupancy would become more flexible under the draft
The July packet proposes that the owner occupy either the primary dwelling or the ADU. That is important for multigenerational housing: an owner could potentially downsize into the ADU while using the main house differently, subject to the final ordinance and other rental rules.
Because this is draft language, do not build a financing or rental plan around it until Centreville confirms the enacted provision.
7. The draft says the ADU cannot be sold separately
The proposed standards state that the ADU may not be separately conveyed from the primary dwelling. In practical terms, this is designed as a second dwelling on the same property—not a separately saleable lot or condominium-style unit under the proposed zoning rule.
8. Existing legal accessory apartments get special treatment
The July draft contains a grandfathering provision for an accessory apartment or ADU lawfully established before the new ordinance under a valid zoning certificate, building permit or special-exception approval. Such a unit could continue under its existing approval despite the new size provision, while an enlargement increasing gross floor area would have to comply with the new standards and other applicable Chapter 170 requirements.
9. Critical Area properties require another layer of review
The draft specifically says an ADU in Centreville’s Critical Area Overlay District must also comply with applicable Critical Area provisions, and where requirements conflict the more restrictive or stringent provision applies.
For those parcels, do not evaluate a backyard ADU only from ordinary setbacks. Environmental buffers, lot coverage and other Critical Area controls can change the usable building envelope.
10. Old nonconforming lots are one reason the 2026 change matters
Centreville Planning Commission minutes identify a real local issue: many historic lots are already nonconforming under modern density standards. Maryland’s new law says an ADU is excluded from density calculations, and the Town has been considering how that interacts with existing nonconformities.
This is a good example of why a generic Maryland article cannot replace a Centreville guide. Older in-Town lots can raise questions that do not appear in a simple statewide size table.
11. Centreville homeowner checklist before paying for plans
- Confirm the parcel is inside Centreville.
- Identify the zoning district and whether the primary use is a single-family detached dwelling.
- Ask whether the 2026 ADU ordinance has been enacted and obtain the final ordinance number/text.
- Confirm the gross-floor-area measurement used for the 75% calculation.
- For a detached unit, check accessory-building setbacks, height, rear-yard footprint and total lot coverage.
- Ask whether one parking space is required and whether your site qualifies for a waiver.
- Confirm owner-occupancy requirements under the final ordinance.
- Check Critical Area Overlay status.
- If an old accessory apartment already exists, bring its zoning certificate/permit/approval to the Town.
- Confirm utilities and building/fire-safety requirements.
- Only then commission final plans or order a prefab unit.
Centreville MD ADU FAQs
Are Centreville ADU rules the same as Queen Anne’s County?
No. Centreville has its own zoning code. Use the County guide only for property under County zoning; an in-Town parcel requires Centreville review.
Does Centreville currently recognize ADUs?
Yes. The Town added an ADU definition to Chapter 170 in 2025. In 2026 the Planning Commission has been developing a more detailed ADU ordinance to align the code with Maryland law.
How big can a Centreville ADU be?
The July 2026 draft proposes a maximum of 75% of the primary dwelling’s gross floor area. Because that language was reviewed in a draft ordinance, confirm final enactment and the measurement method before designing.
Can I build a detached backyard ADU?
The Town’s ADU definition includes detached extensions, and the 2026 draft specifically addresses detached ADUs. A detached unit would also have to satisfy applicable accessory-building standards and site constraints.
Can I convert my garage?
Potentially, but an existing garage is not automatically approved residential space. Confirm its legal status, setbacks, size, utilities and building/fire-safety conversion requirements with the Town.
Does an ADU need another parking space?
The July draft proposes one off-street space but also provides administrative waiver authority. Confirm the final parking provision and waiver criteria before changing your driveway or site plan.
Do I have to live on the property?
The July draft proposes owner occupancy of either the primary dwelling or the ADU. Verify the final enacted language before relying on this arrangement.
Can I sell the ADU separately?
The July draft says the ADU may not be separately conveyed from the primary dwelling.
What if I already have a legal accessory apartment?
The draft contains protection for units lawfully established under prior zoning certificates, permits or special-exception approvals, while later enlargements would need to comply with the new standards. Bring the original approval documents to the Town.
What if my property is in the Critical Area?
The draft requires compliance with applicable Critical Area Overlay provisions in addition to the ADU standards and says the more restrictive provision controls where requirements conflict.
Should I order a prefab ADU now?
Not before confirming the final 2026 ordinance, size measurement, accessory-building envelope, parking, Critical Area status, utilities and building requirements for your parcel.
Primary sources checked
- Centreville Planning Commission — March 4, 2026 Work Session Minutes
- Centreville Planning Commission — January 7, 2026 Agenda
- Centreville Planning Commission — July 15, 2026 Packet
- Centreville Planning Commission — July 1, 2026 Work Session Packet
- Maryland Department of Planning — HB 1466 FAQ
Maryland ADU Guide is an independent research publication, not the Town of Centreville, Queen Anne’s County, a law firm, architect or contractor. Draft ordinance language can change. Confirm the final enacted requirements with the Town before spending money on design or construction.
What to do next
Start by finding the office that reviews your property. A mailing city or a county guide does not establish your parcel’s authority.
- Find Who Reviews My Property.
- Obtain your parcel identifier, survey, floor plans and utility records.
- Ask the reviewing office which current rules, supporting documents and approvals apply.
- Continue to your planning workspace.
Enable JavaScript to prepare a downloadable next-step brief. Planning guidance is not permit approval.