Charlestown MD ADU Rules 2026: Critical Area, Historic Review & State Deadline

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Last researched: September 19, 2026. Charlestown is a Cecil County municipality with its own zoning process, and its ADU situation is more complicated than a simple yes-or-no answer. The Town’s 2025 Comprehensive Plan specifically recommends updating the zoning code to allow accessory dwelling units (ADUs). At the same time, Charlestown’s Critical Area code already contains a detailed accessory-dwelling standard for certain Resource Conservation Area properties, but only where the underlying zoning district permits the use.

Homeowner takeaway: If your property is inside Charlestown, start with the Town rather than Cecil County zoning. Ask which current enacted ADU ordinance or zoning section applies to your parcel, whether the property is in the Chesapeake Bay Critical Area or Historic District, and which Town approvals are needed before the Cecil County building-permit stage.

Charlestown ADU planning snapshot

Question What we verified
Zoning authority Charlestown administers zoning inside Town limits.
Townwide ADU direction The 2025 Comprehensive Plan recommends updating the zoning code to allow accessory dwelling units.
Current zoning terminology Chapter 175 includes “accessory apartment” within its dwelling definitions, but that definition alone does not establish a complete townwide ADU approval pathway.
Critical Area ADU rule Chapter 99 contains a supplemental accessory-dwelling standard for Resource Conservation Area property, but only if the use is permitted by the underlying zoning district.
RCA location/size language The Critical Area provision allows an ADU within the primary dwelling, or with its entire perimeter within 100 feet of the primary dwelling and no more than 900 sq ft of total enclosed area, subject to the section’s conditions.
Historic District Projects in the Historic District may require a certificate of appropriateness before the Town permit can be approved.
HOA documentation The Town’s current permit instructions call for an HOA concurrence letter for Cool Springs at Charlestown and Trinity Woods Preserve.
Permit workflow Town zoning review comes first. For a major project, the Town directs the applicant to Cecil County after Town approval, then requires the County-approved permit information back before final Town issuance.
Final 2026 townwide ADU ordinance I did not locate a clearly posted final townwide 2026 ADU ordinance in the Town materials reviewed on September 19, 2026. Confirm the current enacted rule with Town staff.

Charlestown is not the same zoning jurisdiction as unincorporated Cecil County

A Charlestown mailing address does not by itself prove that the parcel is inside the incorporated Town. If the property is inside Town limits, Charlestown zoning controls the local land-use review. Property outside Town limits may instead be governed by Cecil County zoning.

For property outside the municipality, use our Cecil County ADU Rules guide. If you are unsure who reviews the property, start with the Maryland ADU Jurisdiction Finder.

Charlestown’s 2025 Comprehensive Plan explicitly calls for an ADU zoning update

Charlestown’s 2025 Comprehensive Plan identifies accessory dwelling units as part of the Town’s housing strategy. One of the plan’s recommended actions is to update the zoning code to allow modular and manufactured housing consistent with state law and to allow ADUs.

That statement is important because it shows that the Town itself recognized the need for clearer ADU zoning rules. A comprehensive-plan recommendation, however, is not the same thing as an enacted zoning ordinance. Homeowners still need the current adopted code or ordinance that applies on the date of an application.

Chapter 175 mentions accessory apartments, but a definition is not a permit

Charlestown’s current Chapter 175 zoning materials use the term accessory apartment within the definition of a dwelling. That helps establish that the concept exists in the Town’s zoning vocabulary, but a definition by itself does not tell a homeowner which districts permit an ADU, whether approval is by right or discretionary, or what current size, setback, parking and occupancy standards apply.

During this September 19, 2026 review, I checked the Town’s Planning & Zoning pages, current Chapter 175 materials, Chapter 99 Critical Area provisions, 2026 meeting pages and the 2025 Comprehensive Plan. I did not locate a clearly identified final townwide 2026 ADU ordinance in those public materials. Because Maryland’s October 1 implementation deadline is close, ask Town staff for the ordinance number, adoption date and effective date rather than relying on an older PDF alone.

Charlestown’s Critical Area code already contains a separate ADU standard

Charlestown’s Chapter 99 Critical Area regulations contain a supplemental use standard for an accessory dwelling unit in the Resource Conservation Area (RCA). The section begins with an important condition: it applies only if an accessory dwelling unit is a permitted use in the underlying zoning district.

For qualifying RCA property, the provision allows one additional dwelling unit as part of the primary dwelling, served by the same sewage-disposal system. The unit can be located within the primary dwelling. It can also be arranged so that its entire perimeter is within 100 feet of the primary dwelling, with no more than 900 square feet of total enclosed area, subject to the remaining Critical Area conditions.

The provision also says the accessory unit cannot be subdivided or conveyed separately from the primary dwelling.

The 900 sq ft Critical Area language is not the whole Town ADU rule

It would be a mistake to read the Critical Area section as a blanket 900-square-foot maximum for every Charlestown ADU. Chapter 99 is an environmental overlay. Its ADU language expressly depends on the underlying zoning district permitting the use, and Critical Area requirements continue to apply in addition to general zoning rules.

Maryland’s 2026 ADU framework also limits how restrictive local governments may be on general ADU size, while state environmental and facility-capacity requirements continue to apply. For a Charlestown property in the Critical Area, the safest approach is to ask the Town which general ADU ordinance applies and which Chapter 99 environmental standards are additional constraints on that particular parcel.

Before choosing a plan, use our Maryland ADU size guide and then confirm how Charlestown measures the primary dwelling for the current ordinance.

Historic District review can add another approval layer

Charlestown’s permit guidance says work in the Historic District may require Historic District Commission review and a certificate of appropriateness. The Town asks applicants to provide detailed information about proposed exterior work, including materials, colors and images where applicable.

For an attached addition, garage conversion with exterior changes or a new detached ADU, confirm Historic District status before finalizing the design. A zoning-compliant footprint can still require separate historic-design approval.

Two Charlestown subdivisions have an HOA-document step in the Town workflow

Charlestown’s current permit instructions state that applicants in Cool Springs at Charlestown or Trinity Woods Preserve should obtain a letter of concurrence from the homeowners association before the Town approves the permit.

That Town procedure should be distinguished from a separate legal question: whether a particular private covenant or HOA restriction is enforceable against an ADU under current Maryland law. Maryland now limits private restrictions that unreasonably prohibit or effectively prohibit an ADU, subject to statutory exceptions. If an HOA dispute affects a real project, obtain parcel-specific legal advice rather than treating the Town’s request for a concurrence letter as the final word on covenant enforceability.

Charlestown’s permit workflow is Town first, then Cecil County

Charlestown separates local zoning approval from County building-code review. The Town’s permit instructions direct applicants to submit the Town zoning/building application first. For a major project, after the Town approves the zoning portion, the applicant proceeds to Cecil County for the applicable building permit. The County-approved documentation is then returned to Town Hall so the Town can complete its permit process.

New dwellings, garages and sheds, additions, interior renovations and similar projects are treated as major permits under the Town’s current guidance. The Town lists a $50 fee for a major zoning/building permit and a higher after-the-fact fee if work begins before approval. Confirm the current fee when applying because fee schedules can change.

A usable site plan matters in Charlestown

Charlestown’s application instructions call for site-plan information such as property lines and dimensions, setbacks, existing and proposed structures, and impervious-surface calculations. Those details are especially important for a detached ADU because the Town may need to review both ordinary zoning standards and Critical Area lot-coverage requirements.

Before paying for final architectural drawings, gather a current survey or reliable scaled site plan and identify:

  • property lines and lot dimensions;
  • the primary dwelling and all accessory structures;
  • proposed ADU location and dimensions;
  • driveways and parking areas;
  • setbacks;
  • easements;
  • septic or sewer connections;
  • Critical Area designation, if applicable;
  • Historic District status, if applicable;
  • existing and proposed impervious area.

What to ask Charlestown before spending money

  • What enacted ordinance currently authorizes ADUs townwide?
  • What is the ordinance number, adoption date and effective date?
  • Which residential zoning districts permit an ADU?
  • Are internal, attached and detached ADUs all allowed?
  • What maximum size and measurement method apply?
  • What side and rear setbacks apply to a detached ADU?
  • Does the parcel fall inside the Chesapeake Bay Critical Area?
  • If it is in the RCA, how does Chapter 99’s 100-foot and 900-square-foot language apply?
  • Is the property in the Historic District?
  • Is Historic District Commission approval required?
  • Is an HOA concurrence letter required as part of the Town application?
  • What parking rules and waiver procedures apply?
  • What utility, septic or sewer review is required?
  • Which approvals are issued by Charlestown and which are issued by Cecil County?

Charlestown homeowner checklist

  1. Confirm the parcel is inside Charlestown municipal limits.
  2. Identify the zoning district.
  3. Ask the Town for the current enacted 2026 ADU ordinance.
  4. Check whether the parcel lies in the Chesapeake Bay Critical Area.
  5. If in the Critical Area, identify the applicable designation and Chapter 99 standards.
  6. Check Historic District status.
  7. For Cool Springs at Charlestown or Trinity Woods Preserve, confirm the current HOA-document requirement.
  8. Prepare a scaled site plan or survey.
  9. Confirm ADU size, setbacks, height, lot coverage and parking before final design.
  10. Submit the Town zoning/building application first.
  11. After Town zoning approval, complete the required Cecil County building-permit stage.
  12. Return required County approvals to the Town and complete inspections before occupancy.

Charlestown MD ADU FAQs

Does Charlestown allow ADUs?

Charlestown’s 2025 Comprehensive Plan calls for the zoning code to be updated to allow ADUs, and its Critical Area code already contains an accessory-dwelling standard for certain RCA properties. For a current application, ask the Town for the enacted townwide ADU ordinance and the rules for your zoning district.

Is the Charlestown ADU maximum 900 sq ft?

Do not assume that. The 900-square-foot language appears in Charlestown’s supplemental Critical Area standard for qualifying Resource Conservation Area property. It is not a simple townwide size rule for every parcel.

Can I build an ADU in Charlestown’s Historic District?

A project in the Historic District can require Historic District Commission review and a certificate of appropriateness. Confirm the design-review requirements before finalizing exterior changes or a new detached structure.

Do I need an HOA letter?

Charlestown’s current permit instructions call for an HOA concurrence letter for Cool Springs at Charlestown and Trinity Woods Preserve. Separate Maryland law governs how restrictive private ADU covenants may be, so an HOA dispute should be evaluated on the specific documents and current statute.

Do I apply to Charlestown or Cecil County?

Start with Charlestown for zoning review. For a major project, the Town’s current workflow then sends the approved application to Cecil County for the building-permit stage before final Town issuance.

Who handles zoning questions in Charlestown?

The Town Administrator handles zoning and building permits and zoning/code enforcement. Town Hall is at 241 Market Street, Charlestown, Maryland 21914. The Town lists 410-287-6173 as its main number.

Primary sources checked

Maryland ADU Guide is an independent research publication, not the Town of Charlestown, Cecil County, the Critical Area Commission, a law firm, architect or contractor. Local rules can change during Maryland’s 2026 ADU implementation period. Confirm the current ordinance and parcel-specific requirements with the Town before spending money on design or construction.

YOUR NEXT PRACTICAL STEP

What to do next

Start by confirming which government reviews your property and whether Critical Area or historic-review rules apply.

  1. Find Who Reviews My Property.
  2. Gather your parcel identifier, survey, zoning district and utility information.
  3. Ask the Town which current ADU ordinance and overlay rules apply.
  4. Continue to your planning workspace.

Planning guidance is not permit approval.