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:
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:
Berlin, New Hampshire
Berlin, NH Accessory Dwelling Unit (ADU) Rules
City Acceptance Rating: 5/10
Last Updated: 8.28.2024
Image Source: NH PBS
What You Need To Know
To increase housing options while preserving neighborhood aesthetics, attached ADUs are permitted by the Planning Board through a Conditional Use Permit
Type of ADU Permit Required
Attached ADUs are permitted by the Planning Board through a Conditional Use Permit.
ADU Rules
One ADU Per Property: Only one ADU is allowed per property, and it is not permitted on properties with more than one primary dwelling unit (PDU).
Location: The ADU must be within or added to an existing or proposed single-family dwelling.
Self-Sufficient Living Quarters: The ADU must have its own sleeping, bathing, and eating facilities.
Exterior Changes: Exterior alterations to the PDU are allowed to accommodate the ADU but must not make the PDU look like a duplex or multifamily structure. Access ways should be placed at the side or rear of the building. The ADU should remain functionally dependent on the PDU, with no separate utilities, garages, or driveways. The ADU may have up to two bedrooms.
Size: The ADU must be no larger than 1,000 square feet and must not exceed 40% of the living area of the PDU.
Internal Connection: The ADU must be internally connected to the PDU.
Owner Occupancy: The property owner must live in one of the two units.
Parking: One additional parking space for the ADU must be provided if space is available on the property.
No Separate Ownership: The PDU, ADU, and lot cannot be converted to separate legal ownership. A restrictive covenant must be recorded in the Coos County Registry of Deeds, with copies provided to the Community Development Department and the Assessor before a Certificate of Occupancy is issued.
Septic Requirements: If municipal sewer service is unavailable, the septic system must meet NH Water Supply and Pollution Control Division standards for the combined occupancy of the property.
Resources:
https://www.berlinnh.gov/sites/g/files/vyhlif2811/f/uploads/chapter_17_zoning_ordinance_4-17-23_0.pdf#:~:text=A%20maximum%20of%20one%20(1,3.
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:
Concord, New Hampshire
Concord, NH Accessory Dwelling Unit (ADU) Rules
City Acceptance Rating: 6/10
Last Updated: 8.28.2024
Image Source: Visit Concord
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 Special Exception if 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.Accessory Dwelling Unit (ADU): A residential unit within or attached to a single-family detached dwelling, providing independent living facilities (sleeping, eating, cooking, and sanitation) on the same property as the main dwelling. A house with an ADU counts as two dwelling units.
Permitted Districts: ADUs are allowed by Special Exception in specific districts: RO, RM, RS, RN, RD, RH, CN, CVP, IS, and UT.
Size: ADUs must be between 600 and 750 square feet.
Bedrooms: ADUs can have a maximum of two bedrooms.
Connectivity: ADUs must share a common wall with the main house and have at least one fire-rated interior door connecting the units.
Lot Size: The property must meet the minimum lot size requirements for its district.
Dimensional Requirements: ADUs must comply with all dimensional requirements (frontage, yards, lot coverage, building height) unless the existing building is non-conforming.
Design Guidelines: Any exterior modifications requiring a Building Permit are subject to Development Design Guidelines.
Ownership: The property owner must reside in either the main house or the ADU.
Occupancy: The ADU must be used as a principal residence, not for short-term rentals.
Condominium Conversion: The property cannot be converted to a condominium.
Parking: A minimum of two parking spaces are required, plus one additional space per ADU bedroom.
Address: The ADU must have a separate address and mail receptacle.
Other Requirements:
Fire Separation: Fire separation between units is mandatory.
Septic Tanks: Separate septic tanks are required if municipal sewer is unavailable, but common leach fields are permitted.
Utilities: Separate utilities are not required
Resources:
https://www.concordnh.gov/DocumentCenter/View/18490/ADU-Requirements-docx
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