ADU Rules in Goffstown, New Hampshire

Goffstown is a town of approximately 18,000 residents in Hillsborough County in southern New Hampshire, located on the Piscataquog River directly west of Manchester — New Hampshire's largest city. Goffstown is a classic New England suburban community: a mix of residential neighborhoods, rural areas, and village centers, governed by traditional Town Meeting. Its proximity to Manchester makes it a desirable residential address for commuters, contributing to ongoing housing demand in the area.

New Hampshire RSA 674:71-73 — ADU Rights Statewide

New Hampshire enacted ADU reform legislation (RSA 674:71-73) requiring all New Hampshire municipalities with residential zoning to allow at least one attached ADU by right on any lot containing a single-family dwelling. For Goffstown property owners:

• An attached ADU must be permitted without requiring a special exception, variance, or conditional use permit, provided objective local dimensional standards are met
• The town may set reasonable local standards for setbacks, maximum size, parking, and owner-occupancy requirements
• ADUs cannot be prohibited outright in residential zones

Detached ADUs: RSA 674:71 requires attached ADUs by right; it permits but does not require municipalities to also allow detached ADUs by right. The Town of Goffstown's zoning ordinance determines whether detached ADUs are permitted. Contact the Goffstown Planning or Zoning office to confirm current rules for detached units.

ADU Types Permitted

• Attached ADUs (required by state law by right) — in-law suites, basement apartments, upper-floor units, or additions connected to the primary home
• Detached ADUs — freestanding backyard structures or garage conversions (confirm local rules)
• Garage conversions — converting an existing attached or detached garage into habitable living space
• Interior ADUs — self-contained units created within the primary dwelling's existing footprint

Size, Setbacks, and Dimensional Standards

Goffstown's zoning ordinance establishes local dimensional standards. RSA 674:71 permits municipalities to impose reasonable size requirements but prohibits standards so restrictive that they effectively prohibit ADUs. Contact the Goffstown Planning Department for current standards, which may include:

• Maximum ADU floor area (RSA 674:71 caps local size restrictions — cannot be less than 750 sq ft or 30% of the primary dwelling's floor area, whichever is greater, per state law; verify local implementation)
• Setbacks for detached ADUs from rear and side property lines
• Height limits consistent with accessory structure standards in the applicable zone
• Off-street parking requirements (RSA 674:71 limits how many parking spaces may be required)

Manchester Suburb Context

As a Manchester suburb, Goffstown experiences housing market pressures associated with the greater Manchester metropolitan area. ADUs can serve several purposes in this context:

• Long-term rental units for Manchester-area workers priced out of the city
• Multi-generational living arrangements (in-law suites for aging parents or adult children)
• Supplemental income for homeowners in a relatively high-cost housing market

Owner-occupancy requirements — if Goffstown imposes them — would require the owner to live in either the principal dwelling or the ADU, which affects the economics of building a rental ADU.

Piscataquog River Flood Zone

The Piscataquog River flows through Goffstown, and portions of the town near the river may fall within FEMA-mapped Special Flood Hazard Areas (SFHAs). Properties within an SFHA face additional requirements for any new construction, including ADUs:

• Finished floor elevation must meet or exceed the Base Flood Elevation (BFE)
• A floodplain development permit may be required
• Foundation requirements are more stringent in flood zones

Check flood zone status at the FEMA Flood Map Service Center at msc.fema.gov before planning an ADU near the river.

Permit Process

1. Contact Goffstown's Planning Department or Zoning Administrator to confirm current ADU rules, including whether detached ADUs are permitted by right
2. Confirm FEMA flood zone status for the property
3. Submit a zoning permit application (or verify whether a separate application is required) with site plan and floor plans
4. Obtain a building permit under New Hampshire State Building Code requirements
5. Pass all required inspections and receive a certificate of occupancy

Contact Information

Town of Goffstown Planning Department

• Address: 16 Main Street, Goffstown, NH 03045
• Phone: (603) 497-8990
• Website: goffstown.com

Disclaimer: Zoning regulations and state law change frequently. This page is provided for general informational purposes only. Always verify current ADU requirements with the Town of Goffstown and consult a licensed New Hampshire contractor or architect before beginning any project.