New Hampshire ADU Laws

Complete 2026 guide to accessory dwelling unit regulations

✓Strong Statewide Law

📋Quick Facts

Owner Occupancy
May be required
Parking
Set locally
Approval Process
✓ By-right
Effective Date
1/1/2017

📜Recent Legislation

RSA 674:71-73 (2017) - Original statewide ADU law

Revised ADU law (2025) - Updated and strengthened original statute

⚠️Key Requirements & Restrictions

  • •One ADU permitted by right on all single-family properties
  • •If town ordinance is silent, ADU still deemed permitted accessory use
  • •Manchester requires owner occupancy and common ownership
  • •Standard building, electrical, plumbing permits still required
  • •Can be within, attached to, or standalone structure

📖Detailed Analysis

Strong statewide ADU law - New Hampshire Accessory Dwelling Units statute (RSA 674:71-73) became law in 2017 and was revised/strengthened in 2025. Intent is to expand housing supply without further land development and encourage efficient use of existing housing stock. One ADU permitted by right, and if local ordinance is silent, ADU is still deemed permitted accessory use. New Hampshire Housing (formerly NHHFA) provides municipal and homeowner guidance. Manchester requires owner-occupancy but state law allows more flexibility. New Hampshire was early adopter of statewide ADU mandate, preceding most other states.

🔗Official Resources

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⚠️ Disclaimer

The information provided on this website is for general informational purposes only and does not constitute legal, financial, or professional advice. ADU laws, regulations, and requirements vary by jurisdiction and change frequently. While we strive to keep this information accurate and up-to-date, we make no representations or warranties of any kind about the completeness, accuracy, reliability, or suitability of this information. Always consult with qualified local professionals, including attorneys, architects, and your local planning department, before making any decisions regarding ADU construction or investment. Use of this information is at your own risk.

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Last updated: February 2026