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
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
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:
Gilford, New Hampshire
Gilford, NH Accessory Dwelling Unit (ADU) Rules
City Acceptance Rating: 10/10
Last Updated: 8.28.2024
Image Source: Town of Guilford
What You Need To Know
ADUs are classified as Accessory Apartments. They may be attached or detached and allowed one per lot. Either the primary unit or the ADU must be owner occupied.
Type of ADU Permit Required
By-right if requirements are met. ZBA review needed if using as a short-term rental.
ADU Rules
Single Unit: Only one Accessory Apartment is allowed per lot.
Owner Occupancy: The property owner must live in either the main dwelling or the Accessory Apartment.
Exterior Consistency: The Accessory Apartment must match the exterior appearance and style of the main single-family residence, including entrances.
Bedroom Limit: No more than two bedrooms are allowed in an Accessory Apartment.
Size Requirements: The apartment must be between 300 and 1,000 square feet.
Septic System: If not connected to municipal sewer, the shared septic system must meet all state requirements.
Water System: If not connected to municipal water, the shared water system must comply with state standards and provide adequate water for all occupants.
Parking: There must be off-street parking for at least four vehicles, which can include garage or stacked parking.
Condominium Restriction: If the property is converted to a condominium, the Accessory Apartment must remain an accessory use and cannot be an independent condominium unit.
Attachment: The Accessory Apartment should be attached to the main dwelling, except for detached units that meet specific conditions.
Prohibited Locations: Accessory Apartments are not allowed in Manufactured Housing Parks, Manufactured Housing Subdivisions, Planned Unit Developments, Two-Family Residences, Multi-Family Developments, or Dormitories.
Egress Compliance: Both the main residence and the Accessory Apartment must meet all applicable egress codes.
Building Permit: A building permit is required, and the application must provide sufficient information to verify compliance with all relevant codes and requirements.
Detached Units: Detached Accessory Apartments are allowed if:
Set back at least 25 feet from side and rear property lines.
No taller than 24 feet.
Meets all life safety code requirements.
No bunkhouse is present on the property.
Interior Access: If the Accessory Apartment is attached to the main dwelling, there must be an interior door between the two units.
Zoning Compliance: Accessory Apartments are only allowed in zones where they are listed as a permitted use.
Resources:
https://www.gilfordnh.org/file/1783/Whole_Ordinance_for_Web_2020_pdf.pdf page 28
Exeter, New Hampshire
Exeter, NH Accessory Dwelling Unit (ADU) Rules
City Acceptance Rating: 10/10
Last Updated: 8.28.2024
Image Source: Town of Exeter NH
What You Need To Know
One attached or detached ADUs is allowed per property. 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
Only one accessory dwelling unit (ADU) is allowed per detached single-family home or its accessory structure.
ADUs are not permitted in manufactured housing unless in a zoning district that allows it.
For ADUs within the main structure, the ADU must be less than half the finished floor area but not smaller than 750 square feet. For ADUs in a detached structure, the maximum size is 750 square feet.
One of the dwelling units must be owner-occupied.
Off-street parking spaces must meet the requirements of Article 5.6 of this ordinance.
The structure and lot cannot be converted to a condominium or any other separate ownership. The ADU use must be recorded by deed addendum at the Registry of Deeds.
Before renovations or construction, the owner must prove to the Building Inspector that the septic and water systems meet Town and State standards.
After renovations or construction, the owner must request an occupancy permit from the Building Inspector. The ADU cannot be occupied without this certificate.
A new homeowner who wishes to rent out an ADU must comply with the original permit conditions or apply for a new permit if any changes are desired.
Resources:
Belmont, New Hampshire
Belmont, NH Accessory Dwelling Unit (ADU) Rules
City Acceptance Rating: 10/10
Last Updated: 8.28.2024
Image Source: Town of Belmont NH
What You Need To Know
Belmont allows attached and detached ADUs.
Type of ADU Permit Required
By-right if the following requirements are met.
ADU Rules
A Dwelling Unit Accessory to Residential Use (ADU) is a residential unit located within or attached to a single-family home or its accessory structure, providing independent living facilities for one or more people, including sleeping, eating, cooking, and sanitation, on the same property as the primary dwelling.
The ADU must be within or attached to the primary single-family dwelling or detached accessory structure. The distance between an ADU and the principal dwelling's enclosed living space cannot exceed 100 feet.
The ADU must be attached to the primary dwelling by a common wall, floor, or ceiling in conditioned spaces, when applicable. Conditioned space is defined as an area with heating and/or cooling systems capable of maintaining 68°F in winter and 80°F in summer or directly connected to such a space. An interior door must connect the ADU to the principal dwelling when attached.
The ADU must have a minimum of 300 square feet of net floor area and not exceed 1,250 square feet or 40% of the combined net floor area of both the primary dwelling and the ADU, whichever is larger.
Only one ADU per lot is allowed.
The ADU can have no more than two bedrooms.
Either the principal dwelling or the ADU must be occupied by the property owner.
The ADU must not cause overcrowding or traffic congestion in the neighborhood.
Both the principal dwelling and the ADU must comply with all applicable egress codes.
Exterior changes to the ADU must conform to the character of the neighborhood.
Off-street parking must be provided as follows:
2 spaces for the principal residence.
1 space for the ADU.
Parking surfaces must be consistent with the neighborhood and should not impede traffic, road maintenance, or future improvements.
Resources:
Alton, New Hampshire
Alton, NH Accessory Dwelling Unit (ADU) Rules
City Acceptance Rating: 10/10
Last Updated: 8.28.2024
Image Source: Yankee Magazine
What You Need To Know
The purpose of allowing accessory dwelling units is to enhance Alton’s affordable housing options and make better use of existing homes, while preserving the town's rural, one-family residential character. This initiative aims to provide small rental units that support low-income families and improve the overall housing inventory.
Type of ADU Permit Required
By-right if the following requirements are met.
ADU Rules
Subordination and Aesthetics: The ADU must be clearly subordinate to the main residence and maintain the aesthetic continuity of a single-family home.
One Per Lot: Only one ADU is allowed per lot.
Not Considered Additional Unit: The ADU does not count as an additional dwelling unit for lot size or density calculations.
Location: The ADU must be within or attached to a single-family home or within an accessory structure on the same property. No ADU is allowed on lots with more than one dwelling unit.
Lakeshore Residential District: ADUs in this district are only allowed within or attached to a single-family home and require a Special Exception from the Zoning Board of Adjustment. Specific criteria in SECTION 413 do not apply to ADUs in this district.
Bedroom Limit: The ADU can have no more than two bedrooms.
Size Limits:
Maximum of 1,500 sq. ft. of total floor area.
Must not exceed 35% of the total finished floor space of the main dwelling.
If in an accessory structure, it must not exceed 50% of the structure's floor space or 35% of the main dwelling's finished floor space, whichever is less.
Minimum size of 750 sq. ft. is required.
Entrances and Exits: Any new entrances or exits for the ADU must be located on the side or rear of the main dwelling.
Parking: A minimum of four off-street parking spaces must be provided for the main residence and the ADU.
Sewage Disposal: Prior to constructing an ADU, the sewage disposal system must be approved and meet NH RSA 485-A standards. An approved system must be installed if the existing one is not compliant or needs replacement.
Owner Occupancy: Either the main residence or the ADU must be occupied by the property owner.
Interior Door: An interior door must connect the main residence and the ADU if the ADU is within or attached to the main dwelling.
Ownership: The single-family home, ADU, and lot cannot be converted into separate legal ownerships, such as condominiums.
Prohibited with Certain Dwellings: ADUs are not allowed with multiple single-family dwellings, such as townhouses, or with manufactured housing as defined by NH RSA 674:31.
Resources:
https://www.alton.nh.gov/forms/planning/ZoningOrdinance.pdf - page 23