Alstead, New Hampshire
Alstead, NH Accessory Dwelling Unit (ADU) Rules
City Acceptance Rating: 4/10
Last Updated: 11.7.2024
Image Source: Wikipedia
What You Need To Know
ADUs are allowed in Alstead, and they are evaluated on a case by case basis.
Type of ADU Permit Required
To build an ADU in Alstead, you must go through their special exception process.
ADU Rules
ADUs can be up to 750 square feet
ADUs can be detached.
Going through the special exception process is required
Setbacks for ADUs
30 ft from side or back
75 feet from the center of the road
ADUs must be placed the required distance from utilities on site (well and septic)
Septic approval is required through the state not town
Resources:
Town of Alstead, NH 603-835-2242
Wolfeboro, New Hampshire
Wolfeboro, NH Accessory Dwelling Unit (ADU) Rules
City Acceptance Rating: 9/10
Last Updated: 8.28.2024
Image Source: Wolfeboro Chamber of Commerce
What You Need To Know
Only one ADU is allowed per single-family dwelling, and it must not alter the appearance of the home. The A DU’s area must not exceed 30% of the home's total habitable space or 750 square feet, whichever is larger. The ADU must have an interior door connecting it to the main dwelling and at least one off-street parking space. The property owner must occupy one of the units.
Type of ADU Permit Required
Conditional Use Permit required.
ADU Rules
Only one accessory dwelling unit (ADU) is allowed per single-family dwelling.
Exterior changes to accommodate the ADU are permitted, but they must not alter the appearance of the home to look like a duplex or multifamily structure. The ADU's exterior door should be located on the side or rear of the building whenever possible and must be connected to the main dwelling by an interior door in a common wall.
The ADU's area must not exceed 30% of the single-family dwelling's total habitable floor area or 750 square feet, whichever is larger.
At least one dedicated off-street parking space must be provided for the ADU.
The property owner must live in one of the two units and provide proof of occupancy. The owner-occupied unit cannot be sublet, and both the primary and accessory dwelling units must remain under common ownership.
If the property is not connected to municipal sewer services, the septic system must meet New Hampshire's requirements for the combined system demand, as per RSA 485-A:38
Resources:
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=
Stratham, New Hampshire
Stratham, NH Accessory Dwelling Unit (ADU) Rules
City Acceptance Rating: 10/10
Last Updated: 8.28.2024
What You Need To Know
An ADU must be accessory to an owner-occupied residential property, with the owner residing in either the main home or the ADU. It cannot be converted to a condominium or rented for short-term stays. ADUs must be between 400 and 1,000 square feet, and detached ADUs cannot exceed 50% of the primary residence's size. ADUs must have a compatible design with the main dwelling and be located in the side or rear yard, with detached units appearing as customary accessory structures.
Type of ADU Permit Required
By Right if the following requirements are met.
ADU Rules
Accessory to Owner-Occupied Residential Use The property to which an ADU is to be added must be owner-occupied although the owner may reside in the primary dwelling or the accessory unit.
Ownership The ADU or lot cannot be converted to a condominium or any other form of ownership other than the existing single-family dwelling. The single-family dwelling cannot be a mobile home or condominium or located in a Residential Open Space Cluster Development.
Occupancy The occupancy of the ADU cannot be utilized for short-term rentals or vacation rentals (including through sites like Airbnb and VRBO). At a minimum the ADU must be rented out on a month-to-month basis.
Smaller than 1,000 square feet ADUs must be between 400 and 1,000 square feet including uses such as garages, porches, decks, etc. Additionally a detached ADU shall not exceed 50% of the primary residence or 1,000 square feet whichever is smaller. Detached ADUs cannot include a pool or garage if one already exists on the property.
Adequate Septic Capacity and Potable Water The property owner must provide evidence of adequate septic system design and capacity according to the standards of Stratham and the NHDES Water Division, along with adequate potable water according to the standards of the State of New Hampshire.
Two Parking Spaces Required, No New Driveway Curb Cut A minimum of 2 off-street parking spaces must be provided for both the ADU and the single family dwelling for a total of 4 parking spaces.
Compatible Exterior Design and Located in the Side or Rear Yard The architecture of the ADU must be compatible with the single-family dwelling and in character of the property, and designed so that the property retains the appearance of a single-family dwelling. Detached ADUs must have the appearance of a barn, carriage house, or other customary accessory structure.
Building and Zoning Setbacks For new detached ADUs, the ADU must be set back a minimum of 50 feet from the front property boundary. Detached ADUs must also meet structural, wetlands, and other applicable zoning setbacks.
Resources:
https://www.strathamnh.gov/sites/g/files/vyhlif5051/f/faqs/adu_fact_sheet_with_zo_5.4.pdf
Seabrook, New Hampshire
Seabrook, NH Accessory Dwelling Unit (ADU) Rules
City Acceptance Rating: 6/10
Last Updated: 8.28.2024
Image Source: Town of Seabrook Facebook
What You Need To Know
An ADU cannot be converted into a condominium or be detached from the single-family dwelling. It must be no larger than 750 square feet and have no more than two bedrooms. Two off-street parking spaces are required, and there can be only one ADU per lot. Either the ADU or the main dwelling must be owner-occupied. An interior door must connect the ADU to the primary dwelling, and the ADU must maintain aesthetic continuity with the main home..
Type of ADU Permit Required
By right if the following conditions are met.
ADU Rules
An ADU may not be converted to a condominium;
An ADU may not be detached from the Single-Family Dwelling;
Two off-street parking spaces are required for the ADU;
There shall be no more than one ADU per lot; • Either the ADU or the Single-Family Dwelling shall be owner occupied;
The ADU shall be no larger than 750 square feet; and
The ADU shall contain no more than two bedrooms.
An interior door shall be provided between the primary dwelling unit and the ADU.
The ADU shall maintain an aesthetic continuity with the primary dwelling unit.
Resources:
https://seabrooknh.info/wp-content/uploads/2020/07/Zoning-Ordinance-dated-10-March-2020.pdf
Salem, New Hampshire
Salem, NH Accessory Dwelling Unit (ADU) Rules
City Acceptance Rating: 4/10
Last Updated: 8.28.2024
Image Source:Wicked Northshore
What You Need To Know
One accessory apartment up to 2 bedrooms and 950 square feet, is allowed per single-family home. An interior door must connect the main dwelling and the accessory apartment .and the exterior must maintain a single-family residence appearance. The property owner must live in one of the units and the ADU may not be converted to a condominium.
Type of ADU Permit Required
Review by Planning and Engineering Departments before submitting for a building permit.
Two permits are required: one for structural alterations and one for the ADU. An impact fee of $5,617 is due when applying for a Certificate of Occupancy. A deed addendum is required.
ADU Rules
Only one accessory apartment is allowed per single-family home.
The property owner must live in one of the two units.
The home’s exterior and entrances must maintain the appearance of a single-family residence.
The accessory apartment can have a maximum of two bedrooms and up to 950 square feet of floor space.
Water supply and sewage disposal must comply with RSA 485-A:38.
Off-street parking for at least four vehicles is required, with garage and "piggy-back" parking encouraged.
The property cannot be converted into a condominium or any other separate form of ownership. The accessory apartment must be recorded by deed addendum.
An accessory apartment is not allowed if there is an in-law apartment or family day-care center on the property.
Variances from these conditions are against the spirit and intent of this chapter.
Detached accessory apartments are not allowed.
There must be an interior door connecting the main dwelling and the accessory apartment.
Resources:
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
Nashua, New Hampshire
Nashua, NH Accessory Dwelling Unit (ADU) Rules
City Acceptance Rating: 5/10
Last Updated: 8.28.2024
Image Source: City of Nashua
What You Need To Know
An ADU must be clearly secondary to the main home, limited to 750 square feet, and only one ADU is allowed per lot. The ADU's design must match the primary home's architectural style, and no new entrances can face the street. The owner must live in either the main dwelling or the ADU.
Type of ADU Permit Required
If all requirements are met only standard building permits are needed.
ADU Rules
The accessory dwelling unit (ADU) must be clearly secondary to the primary structure and cannot exceed 750 square feet.
Only one ADU is allowed per lot with a single-family home.
The ADU must not change the single-family character of the home or its neighborhood appearance:
No new entrances or exits for the ADU on the front or street-facing side of the home.
No new curb cuts from the street.
The ADU's exterior design must match the home's architectural style, scale, and materials.
The property owner must live in either the primary dwelling or the ADU as their principal residence.
The property owner must file a covenant with the City of Nashua and the Hillsborough County registry of deeds, stating the property contains an ADU and must comply with all applicable ordinances.
One additional off-street parking space is required beyond the standard for a single-family home.
An interior door must connect the primary dwelling and the ADU.
The primary home and the ADU must remain under the same ownership and cannot be separately sold or converted to condominiums.
ADUs are only allowed with single-family detached homes and are not permitted with manufactured housing.
Resources:
Plaistow, New Hampshire
Plaistow, NH Accessory Dwelling Unit (ADU) Rules
City Acceptance Rating: 4/10
Last Updated: 8.28.2024
Image Source: Best Places
What You Need To Know
ADUs must maintain the appearance of a single-family home, with entrances located on the side or rear. ADUs cannot exceed 1,000 square feet and may have no more than two bedrooms. Either the primary home or the ADU must be owner-occupied, and only one ADU is allowed per parcel. Permits and compliance with safety and building codes are required, and ADUs may be rented, with inspections necessary for leases over one year.
Type of ADU Permit Required
Accessory Dwelling Units (ADUs) require a conditional use permit from the Planning Board before construction or use. Applications for this permit follow the same procedures as site plan review. The Planning Board may grant a condition.
ADU Rules
Design and Appearance: The accessory dwelling unit (ADU) must be designed to maintain the appearance of a single-family dwelling. New entrances should be located on the side or rear of the building. If the ADU is attached to the primary dwelling, there must be a connecting door.
Dwelling Type: The single-family dwelling cannot be a mobile home. ADUs are allowed in condominium units with written approval from the condominium association. Only one ADU is permitted per parcel.
Size: The ADU cannot exceed 1,000 square feet.
Occupancy: Either the primary dwelling unit or the ADU must be owner-occupied.
Bedrooms: The ADU may have no more than two bedrooms.
Ownership Restrictions: The ADU and lot cannot be converted into a condominium or any other form of legal ownership distinct from the single-family dwelling.
Permits and Compliance: Before issuing a building permit for a new ADU or a certificate of occupancy for an existing one, the property owner must provide the Building Inspector with:
A State of New Hampshire-approved septic design, specifying the number of bedrooms in both the primary dwelling and the ADU.
A floor plan at a scale of 1/4 inch to the foot showing the proposed changes to the building.
A sketch plan of the lot, drawn to scale, showing existing and proposed structures and parking.
Utilities: All utilities in the ADU must use the existing utility meters.
Rental and Certificates of Occupancy: ADUs may be rented. The property owner must apply for a certificate of occupancy for any new tenant under a lease of more than one year. The unit must be inspected for compliance with building and life safety codes before the certificate is issued.
Driveway: The driveway for the primary residence and its ADU must provide ingress/egress onto a Class V or better road via a single curb cut.
Transfer of Ownership: If a home with an ADU is sold, the new owner must apply for a certificate of occupancy for the ADU under the provisions outlined in this ordinance.
Location of ADUs: ADUs may be added to a single-family residence, an attached garage, or a detached garage. Garage units may be located on the same floor as the garage or built as a second story.
Resources:
https://www.plaistow.com/sites/g/files/vyhlif1071/f/uploads/2022_zoningordinance_final_0.pdf Page 97
New Market, New Hampshire
New Market, NH Accessory Dwelling Unit (ADU) Rules
City Acceptance Rating: 10/10
Last Updated: 8.28.2024
Image Source: Town of New Market
What You Need To Know
ADUs must be between 200-1,000 square feet, cannot exceed 80% of the main unit's floor area. Only detached ADUs are allowed with manufactured homes. ADUs must maintain design consistency with the primary home, and parking and utility requirements must be met, including water and sewage standards. Bonus space may be granted for installing solar energy systems. Properties with ADUs must submit annual recertification.
Type of ADU Permit Required
An ADU requires only a building permit application unless otherwise required by state statute or the Municipal Code of Newmarket, New Hampshire.
ADU Rules
Prohibitions: The following ADU-related uses are prohibited:
Leasing the principal residence, the ADU, or both for short-term rental.
Converting an ADU into a condominium or any other form of separate legal ownership.
Converting an ADU into a primary dwelling unit unless it becomes the only dwelling unit on the lot.
Constructing an ADU within the 100-year flood plain.
Recertification and Retirement of ADUs: All properties with an ADU must submit an annual ADU recertification application. Failure to do so will result in revocation of the ADU's occupancy. If an ADU is abandoned or converted into the primary dwelling unit, the property owner must comply with all applicable regulations.
Standards: The following standards apply to all ADUs:
Occupancy and Ownership:
The property owner must occupy either the principal dwelling or the ADU as their primary residence. Residency must be demonstrated by evidence of voter or vehicle registration.
When the property is owned by a trust, LLC, or other entities, one dwelling unit must be the primary residence of the trust or LLC beneficiary.
Dimensions:
Living Area: ADUs must be between 200 and 1,000 square feet and cannot exceed 80% of the primary dwelling unit's gross floor area.
Building Setbacks: ADUs must adhere to setback requirements. Exceptions include preexisting accessory buildings and those located at specific distances from the front property line.
Density: A single-family lot with an ADU is exempt from maximum residential density requirements.
Impervious Surface Coverage: Lots cannot exceed 65% impervious surface coverage due to ADU construction. Exceeding this limit requires compliance with stormwater management regulations.
Renewable Energy Systems: A 100 sq. ft. bonus to the maximum ADU size may be applied if a rooftop solar energy system is installed.
ADUs on Single-Family Lots with Manufactured Homes: Only detached ADUs (DADUs) are permitted on lots with manufactured homes.
Building Design:
AADUs and ICADUs: ADUs must be subordinate to the primary dwelling in design, maintain aesthetic continuity, and harmonize entrances with the main structure.
DADUs: Newly constructed DADUs must appear as accessory buildings while maintaining aesthetic continuity with the primary dwelling. Converted accessory buildings must maintain or improve aesthetic harmony with the main dwelling.
Parking: Parking standards for ADUs must be followed, with specific requirements based on lot characteristics.
Water Supply and Sewage Disposal: Adequate water supply and sewage disposal must be provided. Applicable fees for town water and sewer must be paid before issuing a building permit or certificate of occupancy. For properties without town sewer, septic systems must meet New Hampshire Department of Environmental Services requirements.
Resources:
https://www.londonderrynh.gov/sites/g/files/vyhlif4616/f/uploads/adz_0.pdf
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
Londonderry, New Hampshire
Londonderry, NH Accessory Dwelling Unit (ADU) Rules
City Acceptance Rating: 10/10
Last Updated: 8.28.2024
Image Source: Business Magazine
What You Need To Know
ADUs are considered workforce housing and allowed only on properties with an owner-occupied single-family home, with a maximum of one per lot. They do not affect minimum lot size or density calculations. The accessory dwelling must be no larger than 40% of the main home's living area, with no more than two bedrooms, and it must be secondary in size and appearance.
Type of ADU Permit Required
If all requirements are met, only standard building permits are needed.
ADU Rules
1. Accessory to Owner-Occupied Residential Use The property to which an ADU is to be added must be owner-occupied although the owner may reside in the primary dwelling or the accessory unit.
2. Ownership The ADU or lot cannot be converted to a condominium or any other form of ownership other than the existing single-family dwelling. The single-family dwelling cannot be a mobile home or condominium or located in a Residential Open Space Cluster Development.
3. Occupancy The occupancy of the ADU cannot be utilized for short-term rentals or vacation rentals (including through sites like Airbnb and Vrbo). At a minimum the ADU must be rented out on a month-to-month basis.
4. Smaller than 1,000 square feet ADUs must be between 400 and 1,000 square feet including uses such as garages, porches, decks, etc. Additionally a detached ADU shall not exceed 50% of the primary residence or 1,000 square feet whichever is smaller. Detached ADUs cannot include a pool or garage if one already exists on the property.
5. Adequate Septic Capacity and Potable Water The property owner must provide evidence of adequate septic system design and capacity according to the standards of Stratham and the NHDES Water Division, along with adequate potable water according to the standards of the State of New Hampshire.
6. Two Parking Spaces Required, No New Driveway Curb Cut A minimum of 2 off-street parking spaces must be provided for both the ADU and the single family dwelling for a total of 4 parking spaces.
7. Compatible Exterior Design and Located in the Side or Rear Yard The architecture of the ADU must be compatible with the single-family dwelling and in character of the property, and designed so that the property retains the appearance of a single-family dwelling. Detached ADUs must have the appearance of a barn, carriage house, or other customary accessory structure.
8. Building and Zoning Setbacks For new detached ADUs, the ADU must be set back a minimum of 50 feet from the front property boundary. Detached ADUs must also meet structural, wetlands, and other applicable zoning setbacks.
Resources:
https://www.londonderrynh.gov/sites/g/files/vyhlif4616/f/uploads/adz_0.pdf
Laconia, New Hampshire
Laconia, NH Accessory Dwelling Unit (ADU) Rules
City Acceptance Rating: 10/10
Last Updated: 8.28.2024
Image Source: City of Laconia
What You Need To Know
ADUs are allowed only on properties with an owner-occupied single-family home, with a limit of one ADU per lot. They do not affect density or lot size requirements, and the owner must live in either the main residence or the ADU.
Type of ADU Permit Required
Special exception permit, but changing to by-right soon. 8-24-24
ADU requirements are being rewritten to allow detached units.
A meeting next week will discuss updates from Planning Supervisor Rob Mona.
ADU Rules
Owner Occupancy: ADUs are permitted only on properties with an owner-occupied single-family dwelling, with a maximum of one ADU per lot.
Density and Lot Size: ADUs do not count as additional dwelling units for minimum lot size or density calculations.
Owner's Residence: The property owner must occupy either the main residence or the ADU as their primary residence. Temporary absences are allowed, but the owner-occupied unit cannot be rented out during the absence.
Location: ADUs must be in the same building as the main residence unless the lot meets or exceeds the minimum size for the zoning district. In such cases, the ADU can be in a separate structure (e.g., garage, barn) if it meets setback requirements.
Utilities and Living Quarters: ADUs must have self-sufficient living quarters (sleeping, bathing, eating). If in an addition to the main dwelling, the ADU must share utilities with the main residence. Detached ADUs may have separate municipal utility connections.
Water and Sewer: Where municipal services are unavailable, the ADU must comply with RSA 485-A:38 for water supply and sewage disposal.
Interior Connection: An interior door must connect the main dwelling and the ADU.
Size and Bedrooms: ADUs can have up to two bedrooms, must be 300-750 square feet, and if the main unit exceeds 3,000 square feet, the ADU can be up to 25% of the main unit's size.
Design Consistency: The ADU must be smaller, shorter, and consistent in appearance with the main dwelling.
Entrances and Exits: Additional entrances/exits for the ADU must be located on the side or rear. New structures must be behind the building line unless approved by the Zoning Board of Adjustment.
Parking: One parking space must be provided in the rear or side yard for the ADU, with no additional curb cut.
Ownership: The property cannot be converted to a condominium or any other separate legal ownership.
Permits and Safety: A zoning/building permit is required before construction, and a certificate of occupancy must be obtained before occupancy. The ADU must have an interconnected fire alarm system and meet all safety and building codes.
Resources:
Hudson, New Hampshire
Hudson, NH Accessory Dwelling Unit (ADU) Rules
City Acceptance Rating: 4/10
Last Updated: 8.28.2024
Image Source: Town of Hudson
What You Need To Know
An ADU is only permitted in single-family homes and cannot be detached and must maintain the appearance of a single-family home, and new ADU entrances must be on the side or rear. . The property owner must live in either the main dwelling or the ADU. A minimum of four off-street parking spaces is required, with no separate driveway for the ADU. The ADU must be between 350 and 750 square feet, with a maximum of two bedrooms. Only one ADU is allowed per lot, housing no more than two unrelated occupants.
Type of ADU Permit Required
Special permit required.
ADU Rules
An ADU is only allowed in single-family dwellings and is not permitted in two-family or multifamily dwellings, or in any nonresidential structures.
An ADU cannot be a freestanding detached structure or part of any structure detached from the main dwelling. Manufactured housing, RVs, or trailers cannot be used as ADUs.
The owner must occupy either the main dwelling or the ADU. The owner must prove residency in one of the units if requested by the Zoning Administrator.
After modifications, the front of the main dwelling must still look like a single-family home. Any new entrances for the ADU must be on the side or rear of the structure.
There must be at least one shared interior access between the main dwelling and the ADU, with two external exits for each unit.
Separate utility connections or meters for the ADU and the main dwelling are not allowed, except as required by code for common areas.
A minimum of four off-street paved parking spaces must be provided for both the main dwelling and the ADU. There cannot be a separate driveway for the ADU.
The ADU must be between 350 and 750 square feet, and the main dwelling must remain at least 850 square feet after the ADU is added.
An ADU cannot have more than two bedrooms.
A building permit is required before constructing or converting space into an ADU.
The ADU must share the same house number as the main dwelling, and no separate mailbox is allowed.
Only one ADU is allowed per lot in any district.
No more than two unrelated persons can occupy an ADU.
The ADU must have an interconnected fire alarm system with the main dwelling.
The ADU must meet water supply and sewage disposal standards under RSA 485-A:38, but separate systems are not required. Verification must be filed with the Town before a building permit is issued.
Resources:
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=
Hampstead, New Hampshire
Hampstead, NH Accessory Dwelling Unit (ADU) Rules
City Acceptance Rating: 4/10
Last Updated: 8.28.2024
Image Source: Municipal Resources Inc
What You Need To Know
ADUs are only permitted in Residential Zone A and Recreational Zone B on lots meeting specific size requirements. The ADU must be part of or an addition to the main dwelling, be less than 50% of its size, and maintain a single-family appearance Detached ADUs are not allowed.
Type of ADU Permit Required
Accessory Dwelling Units (ADUs) require a conditional use permit from the Planning Board before construction or use. Applications for this permit follow the same procedures as site plan review. The Planning Board may grant a conditional use permit if the following criteria are met:
ADU Rules
Location:
ADUs are allowed only in Residential Zone A and Recreational Zone B.Lot Size:
The lot must meet the full lot size requirements for the zone, as defined by the Soil-Based Lot Size (II-1).Septic System:
The septic system must be sufficient to handle all bedrooms in both the primary dwelling unit (PDU) and ADU, in compliance with RSA 485-A:38. This must be verified by a licensed septic designer and approved by the Hampstead Building Department. Installation is required before the issuance of an occupancy permit.Water Source:
The lot must have an adequate water source to meet the combined needs of the PDU and ADU, either through an off-site public water supply or an on-site well that complies with NH state environmental requirements.Structure and Use:
The ADU must be within or an addition to an existing or proposed single-family dwelling.
The ADU must be less than 50% of the square footage of the PDU and remain incidental and subordinate to it.
The structure must maintain the appearance of a single-family dwelling.
The PDU and ADU must be connected by an interior door.
Only one ADU is allowed per lot.
The ADU may have no more than two bedrooms.
Occupancy in the ADU is limited to two people per bedroom unless the septic system is designed for more occupants.
The lot owner must occupy either the PDU or ADU as their primary residence, providing evidence of such.
The lot must have sufficient off-street parking to meet the needs of both units.
The PDU, ADU, and lot must be owned by the same person.
IV-14.3 Detached Accessory Dwelling Units
Detached Accessory Dwelling Units are not allowed. A detached unit includes any structure connected to another by a breezeway or similar feature.
IV-14.4 Certification
Owners applying to build an ADU in an existing or proposed single-family home must certify that they will occupy either the PDU or ADU as their primary residence. If a lot with an approved ADU is sold, the new owner must sign the same certification, which must be recorded at the owner’s expense in the Rockingham County Registry of Deeds. Failure to file this certification at the time of title transfer invalidates the previous approval.
IV-14.5 Restrictions
The PDU, ADU, or lot cannot be converted into a condominium or any other form of legal ownership distinct from the single-family dwelling.
Resources:
https://www.hampsteadnh.us/sites/g/files/vyhlif661/f/uploads/adu-_zoning_article_3_2017.pdf