PERCH · ADU LEGALITY INDEX · UPDATED 2026-07-17

ADU Laws in New Hampshire — 2026 Guide

Statute summary, size caps, owner-occupancy rules, permit timelines, and a 4-question eligibility quiz. Part of the PERCH ADU Legality Index — one page per state, verified against real statute references and updated as laws change.

4-question eligibility quiz

Q1 · State
What state are you building in?
Q2 · Lot size
How big is the lot?
Q3 · Zoning
What zoning district is the lot in?
Q4 · Property type
Which best describes the build?
Result

Key rules · New Hampshire

Statute summaryNew Hampshire RSA 674:71-73 (2016) permitted attached ADUs by-right in every municipality statewide. One of the earliest strong state ADU statutes.
ADU allowedConditional — depends on jurisdiction
Size cap (sqft)750
Owner-occupancy requiredYes
Permit timeline (days)45-100
Statute citationRSA 674:71-73 (2016)
Last verified2026-07-17

Frequently Asked Questions

Are ADUs legal in New Hampshire?
Yes — New Hampshire permits ADUs by-right statewide per RSA 674:71-73 (2016). Every qualifying municipality must allow at least one ADU pathway on eligible single-family lots.
What are the size limits on an ADU in New Hampshire?
New Hampshire permits ADUs up to approximately 750 square feet per RSA 674:71-73 (2016). Individual municipalities may set lower caps; verify with your city or county planning department before ordering.
Do I need a permit for an ADU in New Hampshire?
Yes — every ADU in New Hampshire requires a building permit issued by the city or county. The permit process typically runs 45-100 days depending on jurisdiction, complexity, and whether discretionary review is triggered.
Can I rent out my ADU in New Hampshire?
Yes — long-term rental of an ADU is generally permitted in New Hampshire. Short-term rental (Airbnb / VRBO under 30 days) is subject to municipal registration and may require additional permits.
Does New Hampshire require owner-occupancy on the primary residence when I have an ADU?
Yes — New Hampshire statute or most municipal ordinances require the property owner to occupy the primary residence when an ADU is present.
What zoning districts allow ADUs in New Hampshire?
Most New Hampshire municipalities permit ADUs in single-family residential zones (R-1, R-2 equivalent). New Hampshire RSA 674:71-73 (2016) permitted attached ADUs by-right in every municipality statewide. One of the earliest strong state ADU statutes. Consult your city zoning code for the specific district table.
How long does an ADU permit take in New Hampshire?
Typical ADU permit timelines in New Hampshire run 45-100 days from application to approval. Fast-permitting counties can move in under 30 days; metro-core jurisdictions with discretionary review can extend to 150+ days.
Are there setback requirements for an ADU in New Hampshire?
Yes — most New Hampshire municipalities apply the same setback requirements to ADUs that apply to the primary structure (typically 5-10 feet rear and side, 15-25 feet front). Some cities apply reduced setbacks specifically for detached ADUs. Verify with your city zoning code.
Can I finance an ADU purchase in New Hampshire?
Yes — several financing pathways cover ADU purchases in New Hampshire: Fannie Mae HomeStyle Renovation, FHA 203(k), construction-to-perm loans, HELOC on the primary residence, and cash. Check with modular-friendly lenders like 21st Mortgage, Cascade Financial, and Triad Financial for the New Hampshire-specific product.
What's the difference between an ADU and a JADU in New Hampshire?
The JADU (Junior ADU) category originated in California and is not a distinct legal category in New Hampshire. Most New Hampshire municipalities regulate internal conversions and detached units under a single ADU/accessory apartment definition.

Related resources

Builders
Find a verified New Hampshire ADU builder
Financing
Match to a modular-friendly lender
Yield
Estimate ADU rental yield in your ZIP
Leaderboard
Top rental-yield ZIPs in New Hampshire