Last researched: September 19, 2026. New Windsor already has a dedicated accessory dwelling unit section in its zoning code. § 215-16 allows an ADU to be attached to the principal dwelling or located within 100 feet of it, limits a lot to one ADU, requires owner occupancy and caps the ADU at 800 square feet or one-third of the principal dwelling’s floor area, whichever is less.
Homeowner takeaway: New Windsor’s existing ADU rules are clearer than many Maryland towns, but several provisions now need a 2026 check. Maryland Planning says covered jurisdictions may not impose an ADU maximum below 75% of the primary detached dwelling. Before paying for plans, ask the Zoning Administrator whether § 215-16 has been amended for HB 1466 compliance and whether the parcel’s existing outbuildings, lot coverage and rental plans create additional constraints.
New Windsor ADU planning snapshot
| Question | What we verified |
|---|---|
| Current ADU section | § 215-16 Accessory dwelling units. |
| Where ADUs are authorized | R-1 and R-2 list an ADU as a conditional use. |
| Approval body | The Board of Appeals has authority to hear and decide conditional uses. |
| Attached or detached? | Both. The ADU may be attached or located within 100 ft of the principal dwelling. |
| Number per lot | One ADU per lot or parcel unless another code provision allows otherwise. |
| Owner occupancy | The property owner must occupy one of the dwelling units on the property. |
| Legacy size rule | 800 sq ft or one-third of the principal dwelling’s total floor area excluding garages and decks, whichever is less. |
| Detached-unit classification | A detached ADU is considered an outbuilding. |
| Outbuilding limit | R-1 and R-2 each say one outbuilding is permitted on each lot. |
| Impervious coverage | Total structures and impervious surfaces on a lot with an ADU may not exceed 75% of the lot area. |
| Rental licensing | Town rental-housing licensing applies; attached accessory apartments in a single-family dwelling are specifically routed to a multiple-family dwelling license. |
| 2026 state-law issue | Maryland Planning says covered jurisdictions may not cap ADUs below 75% of the primary detached dwelling. |
New Windsor already authorizes ADUs in R-1 and R-2
New Windsor’s R-1 and R-2 residential districts both list Accessory dwelling unit as a conditional use.
That means an ADU is not simply a standard by-right accessory use under the current code. The Board of Appeals has authority to hear and decide conditional uses under Chapter 215.
Before commissioning plans, confirm:
- the property is actually inside New Windsor municipal limits;
- the parcel is zoned R-1 or R-2, or whether a later amendment expands ADUs to another district;
- the current conditional-use application requirements; and
- the hearing, notice and site-plan requirements the Board of Appeals will apply.
For property outside Town limits, use our Carroll County ADU Rules guide.
Attached and detached ADUs are both contemplated
§ 215-16 says an ADU may be:
- attached to the principal dwelling; or
- located within 100 feet of the principal dwelling.
An attached ADU must have direct access from outside or through a common hall with direct outside access.
Only one ADU is permitted on a lot or parcel unless another code provision says otherwise.
The one-third / 800-sq-ft cap is the biggest 2026 conflict
New Windsor’s current § 215-16 says the ADU may not exceed 800 square feet or one-third of the total floor area of the principal dwelling, excluding garages and decks, whichever is less.
Maryland’s current HB 1466 framework uses a broader standard. The Maryland Department of Planning says an ADU may be up to 75% of the size of the primary single-family detached dwelling and that a covered jurisdiction may not impose a lower local maximum.
For a 1,800-square-foot primary dwelling:
- one-third is 600 square feet;
- New Windsor’s posted rule therefore limits the ADU to 600 square feet; and
- 75% of the same house is 1,350 square feet.
For a 2,400-square-foot house, one-third is 800 square feet, so the Town’s separate 800-square-foot ceiling still stops the unit there, while 75% equals 1,800 square feet.
That does not mean every larger ADU is automatically approvable. It means New Windsor’s legacy one-third / 800-square-foot ceiling should be checked against any later HB 1466 amendment before it is used as the final legal design limit.
Use our Maryland ADU size guide to understand the statewide framework, then ask the Town how it currently measures the primary dwelling.
Owner occupancy is explicit in the current code
New Windsor’s existing ADU section requires the property owner to occupy one of the dwelling units on the property.
That gives the owner flexibility to live in either the main house or ADU, but the current code does not support an obvious absentee-owner model with both units rented.
Because Maryland’s statewide law does not itself impose one uniform owner-occupancy rule on every jurisdiction, ask whether New Windsor retained, amended or removed this requirement in its final 2026 implementation.
A detached ADU counts as an outbuilding
This is one of New Windsor’s most important parcel-level details. § 215-16 says that a detached accessory dwelling unit shall be considered an outbuilding.
R-1 and R-2 each separately say one outbuilding is permitted on each lot.
That creates a practical question for a property that already has a detached garage, shed or other outbuilding. Before assuming there is room for a second detached structure, ask the Zoning Administrator:
- whether the existing structure already uses the one-outbuilding allowance;
- whether converting that structure to the ADU is allowed;
- whether a detached ADU can replace or be combined with an existing outbuilding; and
- whether a later HB 1466 amendment changes the one-outbuilding rule.
Conversion of an existing garage or outbuilding has an additional code test
New Windsor’s § 215-12 says a garage, shed, outbuilding or other nonresidential structure may not be converted to residential use unless it can meet all applicable zoning requirements, including lot area per family and front, rear and side yards.
The same section says the Board of Appeals is not authorized to waive or vary that conversion requirement.
For a garage conversion, this means an existing structure that is perfectly legal as a garage may still fail the residential-use test if its location or lot conditions do not satisfy the standards applied to the conversion.
Ask the Town whether HB 1466 changes how § 215-12 is applied to a detached ADU conversion, especially because Maryland now limits how restrictive side and rear ADU setbacks can be compared with ordinary accessory structures.
Total impervious coverage is capped at 75%
New Windsor’s § 215-16 says the total coverage of structures and all other impervious surfaces on a lot containing an ADU may not exceed 75% of the lot area.
That means the ADU footprint is not the only thing that matters. The Town can also count existing buildings, driveways and other impervious surfaces when evaluating the site.
A small lot with a large driveway, patio or multiple structures may therefore have less buildable ADU area than the raw setback diagram suggests.
The current code requires a full kitchen and bathroom
New Windsor’s ADU section requires complete bathroom facilities and a complete kitchen. The kitchen must include:
- an installed sink with running water;
- a range or cookstove; and
- a refrigerator.
That distinguishes a legal ADU from a guest room, detached office or finished recreation space without independent dwelling facilities.
If the ADU is rented, New Windsor’s rental-housing license rules matter
New Windsor separately licenses rental housing. The Town’s rental code defines rental housing broadly to include accessory apartments and other dwelling units.
The code is especially specific for a single-family dwelling that contains or is attached to one or more accessory apartments: the owner or agent must apply for a multiple-family dwelling license.
The Town’s current rental application says the rental-license fee is $20 per unit when paid by July 31 and that the license is valid for two years. Fees and procedures can change, so verify the current form before relying on those amounts.
For a detached ADU rental, ask the Town which rental-license class applies and whether an inspection or separate unit registration is required.
New Windsor operates municipal water and sewer
The Town publishes current water and sewer rates and connection fees through its Utilities page. An ADU can increase fixture count, occupancy and service demand.
Before final design, ask whether the project requires:
- a separate meter;
- a new or upsized water connection;
- a new or upsized sewer connection;
- connection or impact fees;
- capacity review; or
- other utility approvals.
We did not find a separately titled 2026 ADU amendment in the current Town document listing
For this September 19, 2026 research pass, we checked New Windsor’s current eCode, R-1 and R-2 district rules, the Town ordinance/document library, rental-housing rules, utilities page and zoning contacts.
The Town’s public document listing surfaced ordinances through 2025 but did not show a separately titled 2026 ADU amendment in the materials reviewed.
That does not prove no amendment has been introduced, adopted but not uploaded, or incorporated directly into the code. With Maryland’s October 1 deadline approaching, ask the Zoning Administrator whether Ordinance 07-03-13-era § 215-16 has been superseded or is scheduled for amendment.
What to ask New Windsor before paying for ADU plans
- Has § 215-16 been amended for HB 1466?
- Are ADUs still limited to R-1 and R-2?
- Is Board of Appeals conditional-use approval still required?
- Does the one-third / 800-square-foot maximum still apply?
- How does the Town calculate Maryland’s 75% size limit?
- Is owner occupancy still required?
- Can an existing garage or outbuilding be converted?
- How does the one-outbuilding-per-lot rule apply if a detached garage or shed already exists?
- What side and rear setbacks apply to a detached ADU?
- How does § 215-12 apply to conversions under Maryland’s current setback framework?
- What parking requirement and waiver process apply?
- Has the Town completed an ADU parking study if additional off-street parking is required?
- What water/sewer connection or capacity requirements apply?
- If the ADU will be rented, which rental-license class applies?
- What zoning, building, electrical, plumbing and occupancy permits are required?
New Windsor homeowner checklist
- Confirm the property is inside New Windsor municipal limits.
- Verify the zoning district.
- Ask the Zoning Administrator for the current ADU ordinance and any 2026 amendment.
- Confirm whether Board of Appeals approval is required.
- Do not design solely around the old one-third / 800-square-foot cap.
- Determine whether the project will be attached or detached.
- For a detached ADU, inventory every existing outbuilding on the lot.
- If converting a garage or shed, verify compliance with § 215-12.
- Check total impervious coverage.
- Confirm owner occupancy, parking and any waiver process.
- Check water and sewer capacity and connection fees.
- If renting, confirm the correct rental-housing license.
- Do not make a non-refundable construction commitment until the Town confirms the current rules.
New Windsor MD ADU FAQs
Does New Windsor allow detached ADUs?
Yes under the current public code. § 215-16 allows an ADU to be attached to the main dwelling or located within 100 feet of it. A detached ADU is treated as an outbuilding.
Which New Windsor zoning districts allow ADUs?
R-1 and R-2 currently list an accessory dwelling unit as a conditional use. Confirm whether a 2026 amendment expands that list.
What is New Windsor’s ADU size limit?
The current posted code says 800 square feet or one-third of the principal dwelling’s floor area excluding garages and decks, whichever is less. Maryland Planning now says covered jurisdictions may not impose an ADU maximum below 75% of the primary detached dwelling, so the current Town rule should be confirmed.
Does New Windsor require owner occupancy?
Yes under the current § 215-16. The property owner must occupy one of the dwelling units on the property. Confirm whether that rule remains unchanged in the Town’s final 2026 implementation.
Can I convert an existing garage to an ADU?
Possibly, but § 215-12 says a garage or other outbuilding cannot be converted to residential use unless it meets all applicable zoning requirements, including yard and lot-area standards. The Board of Appeals cannot waive that specific conversion requirement under the current code.
What if I already have a shed or detached garage?
A detached ADU is considered an outbuilding, while R-1 and R-2 each say one outbuilding is permitted on a lot. Ask the Town how that rule applies when an existing outbuilding is already present.
Do I need a rental license for a rented ADU?
New Windsor licenses rental housing. Its code specifically requires a multiple-family dwelling license when a single-family dwelling contains or is attached to an accessory apartment. Ask which license class applies to a detached ADU.
Who should I contact about a New Windsor ADU?
Start with the Town of New Windsor Zoning Administrator at Town Hall, 209 High Street, New Windsor, Maryland 21776. The Town currently lists Ed Palsgrove as Zoning Administrator and 410-635-6575 as the main Town Hall number.
Primary sources checked
- Town of New Windsor — § 215-16 Accessory Dwelling Units and § 215-12 Conversion of Accessory Structures
- Town of New Windsor — R-1 Residential District
- Town of New Windsor — R-2 Residential District
- Town of New Windsor — Board of Appeals powers
- Town of New Windsor — Zoning Administrator and Board of Zoning Appeals contacts
- Town of New Windsor — Rental Housing Licensing Requirements
- Town of New Windsor — Water & Sewer Information
- Town of New Windsor — Ordinance and document library
- Maryland Department of Planning — HB 1466 ADU FAQ
Maryland ADU Guide is an independent research publication, not the Town of New Windsor, Carroll County, a law firm, architect or contractor. This page reports New Windsor’s current public § 215-16 ADU standards and compares them with Maryland’s current HB 1466 framework. Confirm any 2026 amendment, Board of Appeals requirements and parcel-specific conditions with the Town before spending money on design or construction.
What to do next
Confirm the current § 215-16 text and your outbuilding situation before choosing an ADU size or detached-unit layout.
- Confirm who reviews the property.
- Ask New Windsor whether § 215-16 has been amended for HB 1466.
- Gather your zoning district, survey, existing outbuildings, floor area and utility information.
- Continue to the Maryland ADU planning tools.
Planning guidance is not permit approval.