Windham, New Hampshire
Windham, NH Accessory Dwelling Unit (ADU) Rules
City Acceptance Rating: 8/10
Last Updated: 8.28.2024
Image Source: Town of Windham
What You Need To Know
Only one attached ADU is allowed per single-family dwelling, with a maximum size of 950 square feet and two bedrooms. The property owner must reside in either the main home or the ADU as their primary residence. ADUs are prohibited in townhouses and manufactured housing. The ADU must maintain the appearance of a single-family residence and the cannot be converted to a condominium or separate legal ownership.
Type of ADU Permit Required
If all requirements are met, only standard building permits are needed.
ADU Rules
Only one accessory dwelling unit (ADU) is allowed per single-family dwelling and must be attached.
ADUs are prohibited for townhouses and manufactured housing as defined in RSA 674:3.
The property owner must occupy either the principal dwelling or the ADU as their primary residence.
The property and use must comply with all Town of Windham Zoning Ordinance, Land Use Regulations, and applicable building, life safety, and health codes.
The property owner may be required to periodically demonstrate compliance with the Town, with reasonable advance notice.
Any exterior entrances of the principal and accessory dwelling units must be designed to maintain the appearance of a single-family residence.
An interior door, which may be locked, must be provided between the principal and accessory dwelling units.
The ADU may not exceed 950 square feet and can have a maximum of two bedrooms.
The principal and accessory dwelling units must share a single driveway.
Septic and water systems must meet NH DES and Town requirements for combined or separate systems for both units.
Off-street parking must be provided for one additional vehicle.
The structure and lot cannot be converted to a condominium or any other distinct form of legal ownership. To ensure compliance, the property owner must execute a restrictive covenant, easement, or development restriction deed in favor of the Town, which must be recorded in the Rockingham County Registry of Deeds and a copy provided to the Community Development Department and the Assessor before a Certificate of Occupancy is issued.
Resources:
https://windhamnh.gov/DocumentCenter/View/14860/2024-Zoning-Ordinance-?bidId=
Rochester, New Hampshire
Rochester, NH Accessory Dwelling Unit (ADU) Rules
City Acceptance Rating: 8/10
Last Updated: 8.28.2024
Image Source: City of Rochester NH
What You Need To Know
ADUs must be accessory to a single-family home, limited to 800 square feet and two bedrooms. ADUs can be part of the main dwelling or in a separate structure, with only one allowed per lot and detached requiring special approval. The property owner must live in one of the units, and at least one parking space is required. Security and caretaker apartments, up to 800 square feet, are allowed in commercial or residential buildings with specific occupancy restrictions.
Type of ADU Permit Required
Permitted as specified in the Tables of Uses (by right or by special exception). Detached units require special exception approval.
ADU Rules
Permitted as specified in the Tables of Uses (by right or by special exception). Detached units require special exception approval.
Accessory to a single-family dwelling and, if detached, must match the architectural style.
Limited to two bedrooms or less.
Maximum size of 800 square feet.
Can be part of the single-family dwelling or in a separate building (e.g., above a garage). If part of the main dwelling, an interior door is required.
Only one ADU is allowed per lot.
The property owner must occupy one of the dwelling units as their principal residence.
At least one parking space must be provided for the ADU.
If there is no municipal sewer, the septic system must meet NHDES requirements for total occupancy.
Exempt from site plan review, but a letter of intent must be submitted to the Building Inspector to confirm compliance with these conditions.
Security apartments (up to 800 square feet) must be attached to or located within a commercial, office, or industrial building. Occupancy is restricted to the business owner, family member, or employee for security purposes. Requires site plan review.
Caretaker apartments (up to 800 square feet) must be attached to or located within a residential or nonresidential building. Occupancy is restricted to the owner, family member, or employee of the principal use. Requires site plan review.
Resources:
Raymond, New Hampshire
Raymond, NH Accessory Dwelling Unit (ADU) Rules
City Acceptance Rating: 8/10
Last Updated: 8.28.2024
Image Source: Raymond NH Facebook
What You Need To Know
One attached ADU is permitted per parcel in districts allowing single-family homes. The ADU must be secondary in size and use, with no additional lot size required. The property owner must live in either the main home or the ADU as their primary residence. The ADU must match the main dwelling’s design, with entrances on the side or rear unless shared with the main entrance.
Type of ADU Permit Required
If all requirements are met, only standard building permits are needed.
ADU Rules
Only one accessory dwelling unit (ADU) is allowed per parcel with a single-family home in districts that permit single-family dwellings.
The ADU must be clearly secondary to the main dwelling in size, use, and purpose.
No additional lot size or space requirements are needed beyond those for a single-family home, but a zoning determination and building permit are required for ADUs.
An ADU can qualify as workforce housing if it meets rental unit criteria under RSA 674:58 IV.
The property owner must live in either the main dwelling or the ADU as their primary residence.
Proof of residence must be provided to the Assessor's office by January 1.
The exterior of the ADU must match the main dwelling's design and appearance. If the ADU entrance faces the street, it must share the main entrance, with additional entrances placed on the side or rear. The Code Enforcement Officer will review designs before issuing a building permit.
The ADU can have a maximum of two bedrooms.
The ADU must be between 500 and 1,000 square feet or up to 1/3 of the total heated area of both units, whichever is larger.
There must be an interior connecting door between the main dwelling and the ADU.
At least four off-street parking spaces must be provided.
The property must have adequate vehicle access, with only one driveway serving both units.
A plan approved by the New Hampshire Department of Environmental Services is required to handle any increased waste from the ADU.
Detached ADUs are not allowed in the Town of Raymond.
Resources:
Portsmouth, New Hampshire
Portsmouth, NH Accessory Dwelling Unit (ADU) Rules
City Acceptance Rating: 8/10
Last Updated: 8.28.2024
Image Source: Meredith NH
What You Need To Know
Portsmouth has create an easy to follow flowchart and process for homeowners who are interested in ADUs. Minimal requirements allow for flexibility in building ADUs in Portsmouth.
Type of ADU Permit Required
Requires Planning Department approval process. Once approved, submit for a building permit.
ADU Rules
750 sq. ft max gross living area entirely within a single-family dwelling or 600 sq. ft. gross living area in a detached accessory building that complies with dimensional standards in certain zone districts.
Same ownership.
1 parking space is required.
If connected, an interior door is required.
Accessory Dwelling Unit Application Instructions
Create an ADU in Portsmouth Flowchart
Resources:
https://www.cityofportsmouth.com/planportsmouth/accessory-dwelling-units-adu
Meredith, New Hampshire
Meredith, NH Accessory Dwelling Unit (ADU) Rules
City Acceptance Rating: 8/10
Last Updated: 8.28.2024
Image Source: Meredith NH
What You Need To Know
ADUs must be secondary to the main house and maintain the home's single-family appearance with new entrances placed on the side or rear. ADUs should be 300 to 800 square feet, not exceed 30% of the main home's floor area. ADUs cannot be used for short-term rentals except for Bed and Breakfasts.
Type of ADU Permit Required
ADUs are permitted by special exception from the Board of Adjustment in any district, following these regulations.
ADU Rules
Secondary Unit: ADUs must be secondary to the main house and must not change its appearance as a single-family home. Only one ADU is allowed per house and lot, and it must have its own house number.
Exterior Changes: Any exterior changes should not alter the look of the home. New entrances should be placed on the side or rear.
Lot Size: ADUs don’t require extra lot size beyond what’s needed for the main house.
Detached ADUs: Detached ADUs are allowed only on larger lots and cannot be converted into main houses.
Size: ADUs must be between 300 and 800 square feet and take up no more than 30% of the total floor area.
Integration: Attached ADUs should be easy to merge back into the main house and must share an internal connection.
Septic System: The septic system must be certified to handle the additional waste. If the current system isn’t adequate, it must be upgraded.
Parking: There must be enough off-street parking for both units.
Access: The property must allow safe entry and exit for vehicles.
Use Restrictions: ADUs cannot be used for short-term rentals like hotels or motels, except for Bed and Breakfasts.
Resources:
https://www.hollisnh.org/sites/g/files/vyhlif3271/f/uploads/holliszoningordinance2024_0.pdf page 14
Manchester, New Hampshire
Manchester, NH Accessory Dwelling Unit (ADU) Rules
City Acceptance Rating: 8/10
Last Updated: 8.28.2024
Image Source: Office of the Mayor Facebook
What You Need To Know
Only one ADU is allowed per single-family home, which can be within, attached to, or above the garage, or as a standalone structure. The owner must live in either the main dwelling or the ADU, and both must remain under common ownership. ADUs cannot exceed 900 square feet. The design must match the main house, and new ADUs require a conditional use permit and impact fees.
Type of ADU Permit Required
Conditional Use Permit required.
ADU Rules
Quantity: Only one ADU is allowed per single-family home. It can be within, attached to, or above the garage, or as a standalone structure. Garage ADUs must not reduce required parking space.
Owner Occupied: The owner must live in either the main dwelling or the ADU. Both units must stay under common ownership and cannot be separately sold. A deed restriction requiring owner occupancy must be recorded before occupancy.
Size: ADUs cannot exceed 900 square feet or the height of the main structure and are limited to two bedrooms.
Location: ADUs are not allowed in front yards and must be at least 10 feet from side and rear property lines, with detached ADUs at least 5 feet from the main structure.
Parking: One additional off-street parking space is required for the ADU.
Utilities: Septic systems must meet NH standards for the total occupancy. ADUs must connect to existing utilities if available.
Design and Construction: New entrances for ADUs cannot face the street. The design must match the main residence.
Internal Construction: ADUs within existing structures do not require a conditional use permit, even with minor exterior changes.
External Construction: New construction for ADUs requires a conditional use permit and must match the main home's exterior design.
Impact Fees: New ADUs require the payment of impact fees as per Article 13.
Resources:
https://www.manchesternh.gov/Portals/2/Departments/pcd/Forms/AccessoryDwellingUnits-Information.pdf
Hollis, New Hampshire
Hollis, NH Accessory Dwelling Unit (ADU) Rules
City Acceptance Rating: 8/10
Last Updated: 8.28.2024
Image Source: Town of Hollis
What You Need To Know
ADUs must be secondary to the main house and maintain the home's single-family appearance with new entrances placed on the side or rear. ADUs should be 300 to 800 square feet, not exceed 30% of the main home's floor area. ADUs cannot be used for short-term rentals except for Bed and Breakfasts.
Type of ADU Permit Required
ADUs are permitted by special exception from the Board of Adjustment in any district, following these regulations.
ADU Rules
Secondary Unit: ADUs must be secondary to the main house and must not change its appearance as a single-family home. Only one ADU is allowed per house and lot, and it must have its own house number.
Exterior Changes: Any exterior changes should not alter the look of the home. New entrances should be placed on the side or rear.
Lot Size: ADUs don’t require extra lot size beyond what’s needed for the main house.
Detached ADUs: Detached ADUs are allowed only on larger lots and cannot be converted into main houses.
Size: ADUs must be between 300 and 800 square feet and take up no more than 30% of the total floor area.
Integration: Attached ADUs should be easy to merge back into the main house and must share an internal connection.
Septic System: The septic system must be certified to handle the additional waste. If the current system isn’t adequate, it must be upgraded.
Parking: There must be enough off-street parking for both units.
Access: The property must allow safe entry and exit for vehicles.
Use Restrictions: ADUs cannot be used for short-term rentals like hotels or motels, except for Bed and Breakfasts.
Resources:
https://www.hollisnh.org/sites/g/files/vyhlif3271/f/uploads/holliszoningordinance2024_0.pdf page 14
Hampton, New Hampshire
Hampton, NH Accessory Dwelling Unit (ADU) Rules
City Acceptance Rating: 8/10
Last Updated: 8.28.2024
Image Source: NH State Parks
What You Need To Know
Applicants proposing an ADU must submit a scaled plan to the Hampton Planning Board showing the ADU, property line distances, and parking spaces. They must also provide scaled exterior elevations and floor plans showing the interior layout of the ADU.
If the proposal involves enlarging a building or increasing the impervious coverage of the lot, and the Building Inspector has concerns about meeting dimensional requirements, the applicant must submit a certified plot plan by a licensed New Hampshire land surveyor with existing and proposed setbacks and impervious coverage calculations. The Building Inspector’s determinations can be appealed to the Zoning Board of Adjustment.
Type of ADU Permit Required
A Conditional Use Permit from the Hampton Planning Board and a Building Permit in accordance with the Hampton Zoning Ordinance is needed.
ADU Rules
An ADU must provide independent living facilities, including sleeping, eating, cooking (stove, refrigerator, sink), and sanitation (shower/tub, toilet, sink).
It can have up to two bedrooms, each between 7x10 feet and 200 square feet.
The owner must occupy either the main dwelling or the ADU as their primary residence.
Each bedroom in the ADU can house no more than two people.
ADUs or the main dwelling cannot be rented for less than six months.
A Certificate of Rental Occupancy is required for rental units.
ADUs cannot be used for business purposes.
ADUs can be used by relatives of the owner without following the rental rules, but a notarized attestation is required.
ADUs must be attached to the main dwelling, with an interior door connecting them.
For buildings with three or more stories, additional egress is required for upper-story ADUs.
Detached ADUs may be permitted under certain conditions, with a maximum footprint of 5% of the lot area.
Enlarging a structure with a detached ADU is prohibited.
ADUs cannot exceed 800 square feet.
ADUs must comply with Wetlands Conservation District regulations.
ADUs must connect to the town sewer or a legal private system, with proper design to prevent freezing.
If using a private well, it must provide sufficient water for both the main dwelling and the ADU.
ADUs must follow the dimensional requirements in Article IV of the Hampton Zoning Ordinance.
ADUs attached to dwellings of three or more stories require sprinkler systems in both units.
ADUs and the main dwelling must remain under the same ownership and cannot be converted to condos.
ADUs are subject to impact fees, equal to the fee for a two-unit structure, with no waivers.
Resources:
www.hamptonnh.gov/DocumentCenter/View/1697/Accessory-Dwelling-Unit-Ordinance?bidId=
Durham, New Hampshire
Durham, NH Accessory Dwelling Unit (ADU) Rules
City Acceptance Rating: 8/10
Last Updated: 8.28.2024
Image Source: Derry Community Access Media
What You Need To Know
Attached & detached ADUs are allowed and can not exceed 850 square feet. The homeowner must occupy the primary residence or ADU. Minimum occupancy is 4 weeks.
Type of ADU Permit Required
A conditional Use Permit is required before any building permit will be issued. Applications shall include proof that the following relevant requirements have been met.
ADU Rules
Must be between 500 and 750 square feet, with a total area not exceeding 850 square feet or the size of the primary dwelling.
Limited to a maximum of two bedrooms.
Must not increase any nonconforming aspects of the primary structure or cause a conforming lot to become nonconforming.
No additional driveway is allowed, but at least one off-street parking space per bedroom is required.
The property owner must live in either the primary dwelling or the ADU.
Minimum occupancy for an ADU is four weeks.
Business use of an ADU is limited to a home occupation.
The ADU’s appearance, style, color, and design must match the primary dwelling or structure to which it is attached.
ADUs cannot be used for transient or temporary housing like hotels, motels, or boarding houses.
On conforming lots, ADUs can be attached, detached, or standalone; on nonconforming lots, only attached ADUs are permitted.
ADUs cannot be built with a duplex or multifamily dwelling and cannot attain the status of a duplex or multifamily dwelling.
Attached ADU Standards:
Must be contiguous to the primary dwelling.
Must share a common wall, floor, or ceiling with the primary dwelling.
Must have an interior door connecting the primary dwelling and the ADU.
Detached ADU Standards:
Permitted on conforming lots if they meet building requirements, including setbacks, water supply, septic, and driveway regulations.
Standalone ADU Standards:
Allowed only on lots with an area 50% larger than the required size for a conforming lot.
Derry, New Hampshire
Derry, NH Accessory Dwelling Unit (ADU) Rules
City Acceptance Rating: 8/10
Last Updated: 8.28.2024
Image Source: Derry Community Access Media
What You Need To Know
Attached ADUs only are allowed and can not exceed 800 square feet. The homeowner must occupy the primary residence or ADU.
Type of ADU Permit Required
Permitting By Right if all requirements are met, only standard building permits are needed.
ADU Rules
The lot must meet the minimum area required for its zoning district.
Sewer disposal provisions must comply with state law.
Off-street parking for at least four vehicles is required.
The ADU’s living space cannot exceed 800 square feet.
The ADU must be within or attached to the existing home and have an interior door connecting it to the main dwelling.
Converting a free-standing structure into an ADU is prohibited.
The ADU must include a kitchen, living room, bathroom, and one or two bedrooms.
Room sizes must meet the International Residential Code standards.
Once an ADU is created, no further conversion for additional dwelling units is allowed.
The property and structure cannot be converted into a condominium or other separate ownership.
Any additions for the ADU must match the design of the primary dwelling.
The owner must occupy either the primary or accessory dwelling unit.
Resources:
Conway, New Hampshire
Conway, NH Accessory Dwelling Unit (ADU) Rules
City Acceptance Rating: 8/10
Last Updated: 8.28.2024
Image Source: Expedia
What You Need To Know
ADU regulations are fairly relaxed. Attached, detached ADUs allowed must be 300 -800 square feet in size and must not be used for short term rental.
Type of ADU Permit Required
By-right.
ADU Rules
A dwelling unit accessory to a single-family dwelling, either attached or detached. Such accessory dwelling units shall be not less than 300 square feet and no greater than 800 square feet.
The accessory dwelling unit is designed to ensure architectural compatibility with the neighborhood.
Sufficient parking is located on site.
Both the primary single-family dwelling and the accessory dwelling unit shall be used for long-term residency, and short-term transient occupancy of either dwelling unit is prohibited.
Resources:
Bedford, New Hampshire
Bedford, NH Accessory Dwelling Unit (ADU) Rules
City Acceptance Rating: 8/10
Last Updated: 8.28.2024
Image Source: Town of Bedford NH
What You Need To Know
The Town of Bedford permits Accessory Dwelling Units, commonly abbreviated to ADUs, to provide additional opportunities for housing in the community. Bedford allows one accessory dwelling unit per single-family parcel, subject to requirements.
Detached Accessory Dwelling Units are separate apartments that are detached from single family homes and located on the same parcel. ADUs offer several benefits for homeowners, including allowing a separate attached living space for relatives, or providing an additional stream of income to rent the units to tenants. The Town does not regulate who resides in an ADU.
Type of ADU Permit Required
Conditional Use Permit from the Planning Board
ADU Rules
ADU Size and Use: The ADU must be smaller than 1,000 square feet and clearly secondary to the primary residence. It should not exceed 50% of the size of the main house.
Detached ADUs in RA District: Detached ADUs are allowed in the Residential & Agricultural (RA) District but require a Conditional Use Permit from the Planning Board.
Septic System Requirements: If the property uses a septic system, it must be approved by the NH Department of Environmental Services to ensure adequate capacity for both the main house and the ADU.
Minimum Lot Size: The combined size of the main house and the detached ADU must meet the minimum lot size requirements for the RA District according to the Zoning Ordinance.
No Short-Term Rentals: The ADU cannot be rented for less than 30 consecutive days. Short-term rentals through platforms like Airbnb or VRBO are not allowed. The ADU or main house can be rented on a month-to-month basis, but one must be owner-occupied.
Ownership: The ADU or lot shall not be converted to a condominium or any other form of legal ownership distinct from the ownership of the single dwelling.
Parking Requirements: One parking space must be available for the ADU, using the existing driveway. No new driveway curb cuts are allowed.
Exterior Design and Location: The exterior design of the ADU should match the main house in materials, style, and scale. The ADU should be located in the side or rear yard and have no more than two bedrooms.
Building Permit: A building permit is required for ADUs. Contact the Building Department for details. ADUs built without a permit are not recognized by the Town and could affect future property sales.
Contact Information: For questions about ADUs, contact the Planning Department at (603) 472-5243, or the Building Department for permit-related inquiries at (603) 472-3833.
Impact Fees: Before the ADU can be occupied, impact fees must be paid to the Town. The total fee is $1,159, covering school and recreation impact fees.
Resources:
https://www.bedfordnh.org/DocumentCenter/View/5786/Detached-ADU-Fact-Sheet---2022-