Hampstead, NH Accessory Dwelling Unit (ADU) Rules

City Acceptance Rating: 4/10

Last Updated: 8.28.2024

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

Hampstead, New Hampshire