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Zoning Guide

ADU Rules in Keene, New Hampshire

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ADU Rules in Keene, New Hampshire

Keene is the commercial and cultural hub of Cheshire County in southwest New Hampshire, with a population of approximately 23,000. Home to Keene State College and a vibrant downtown, Keene offers a mix of Victorian-era housing, newer suburban neighborhoods, and college-area rentals. The Ashuelot River flows through the city, creating both scenic character and flood zone considerations. Property owners in Keene benefit from New Hampshire's strong statewide ADU mandate.

New Hampshire Statewide ADU Law (RSA 674:71-73)

New Hampshire's RSA 674:71-73 (enacted 2017, strengthened by 2021 amendments) establishes the foundation for ADU construction in Keene:

  • One ADU by right: Keene must allow at least one accessory dwelling unit as of right on any single-family residential lot. No variance or special exception is required for code-compliant ADUs.
  • Administrative approval: State law requires that compliant ADUs be approved administratively — no public hearing or discretionary review is permitted.
  • Owner-occupancy: The 2021 amendment (RSA 674:73) limited conditions municipalities can impose, including owner-occupancy requirements. Verify Keene's current conditions with Planning and Development.
  • State law prevails: Where Keene's local zoning conflicts with RSA 674:71-73, state law governs.

Permitted ADU Types in Keene

  • Detached ADU: A separate, standalone structure on the same lot
  • Attached ADU: An addition to the primary dwelling with a separate entrance
  • Interior ADU: A unit created within the existing home, such as a basement conversion or attic/upper-floor unit
  • Garage conversion: Converting an attached or detached garage into a self-contained dwelling unit

Confirm which ADU types are allowed in your specific zoning district with Keene Planning and Development.

General Size and Dimensional Standards

Standard General Guidance
Maximum ADU Size Verify with city — local ordinance governs
Minimum Lot Size Per underlying zoning district
Side/Rear Setbacks Typically 5–10 ft; verify locally
Maximum Height Per underlying zone
Parking Typically 1 additional space; verify locally

Confirm current standards with Keene Planning and Development, as requirements vary by zoning district.

Special Overlay Considerations

Ashuelot River Flood Zones: The Ashuelot River and its tributaries flow through Keene. Properties in FEMA AE flood zones must comply with Keene's Floodplain Management Ordinance, including elevated construction standards and restrictions on below-grade habitable space.

Keene State College Neighborhood: Properties near Keene State College may be in residential zones with specific density or use limitations. Verify your zone and any overlay designations with Planning and Development.

Downtown Historic Area: Keene's downtown features historic 19th-century commercial and residential architecture. Properties in designated historic overlay areas may require design review from the Historic District Commission for exterior modifications, including new ADU entrances and additions.

Southwest NH Regional Character: Keene is somewhat more isolated than the Seacoast or southern NH communities, with a strong local economy centered on education, healthcare, and retail. ADU rentals are common in the college-area neighborhoods.

Permit Process

  1. Zoning verification: Confirm your lot's zoning district and overlay zones through Keene's zoning map or Planning and Development.
  2. Pre-application consultation: Meet with Planning and Development staff to review your proposed ADU concept before investing in detailed plans.
  3. Plan preparation: Work with a licensed architect or designer; plans must conform to NH State Building Code (RSA 155-A, IBC/IRC based).
  4. Building permit application: Submit application and plans to Keene's Planning and Development — Building Division.
  5. Administrative review: Code-compliant ADUs are reviewed without a public hearing under RSA 674.
  6. Inspections: Schedule all required inspections during and after construction.
  7. Certificate of occupancy: Obtain CO before occupying the ADU.

Contact Information

Disclaimer

ADU regulations in Keene are subject to change. This page is for informational purposes only and does not constitute legal or planning advice. Always verify current requirements with the City of Keene Planning and Development Department and review NH RSA 674:71-73 for statewide ADU rights. Consult a licensed architect, contractor, or land use attorney before beginning any project.

More about Keene Zoning

Sources

  1. City of Keene Zoning Ordinance·library.municode.com·Accessed 2026-04-07·Direct link
  2. NH RSA 674:71-73 — Accessory Dwelling Units·gencourt.state.nh.us·Accessed 2026-04-07·Direct link

FAQ

Are ADUs allowed in Keene, New Hampshire?
Yes. New Hampshire RSA 674:72 requires Keene to allow at least one accessory dwelling unit as of right on any single-family lot in a residential zone. Keene's zoning ordinance must comply with this state mandate.
Does Keene State College affect ADU rules?
Keene State College generates rental housing demand that makes ADUs economically attractive. The college does not directly change zoning rules, but properties near campus may be in specific residential zones with their own dimensional standards. Always verify your zone with Keene Planning and Development.
Are there flood zone restrictions near the Ashuelot River in Keene?
Yes. The Ashuelot River flows through Keene, and some properties are in FEMA Special Flood Hazard Areas. ADUs in these areas must comply with Keene's Floodplain Management Ordinance, typically requiring elevated construction and restricting habitable basement space.