Straight answers

Can you put a tiny house in your backyard in New Hampshire?

Yes, if it is built as a detached accessory dwelling unit on a foundation. Under RSA 674:72 a municipality must allow accessory dwelling units in all zoning districts that permit single-family dwellings, and one unit, attached or detached, is allowed as a matter of right. RSA 674:73 says it again for the detached case: a municipality shall permit one detached accessory dwelling unit. The unit can be up to 950 square feet unless your town authorizes more, and the town may not restrict it to less than 750 square feet. A tiny house on wheels does not inherit any of this, because neither the accessory dwelling unit statutes nor the state building code mentions one.

Figures verified against the sources below · October 1, 2026

01 — The longer answer

What New Hampshire requires, and what your town still decides

What the state makes every town allow

RSA 674:72 goes further than the headline. The town must allow the unit without additional requirements for lot size, setbacks, aesthetic requirements, design review, frontage or space limitations beyond what a single-family home without an accessory unit would need. It may not require a family relationship between the people in the two homes, may not limit the unit to one bedroom, and may not deny it a separate electrical panel and service. The section was rewritten with effect from 1 July 2025 and amended again with effect from 31 August 2026, so guidance written before then describes a weaker law than the one in force.

What a town can still ask for

A town may require the owner to live in one of the two homes, though it cannot say which one. Where it requires parking for the main house, it may require up to one additional space for the accessory unit, and that space can be on the lot or at a legally dedicated off-site location, at the owner's choice. The applicant has to make adequate provision for water supply and sewage disposal, which on a lot with a septic system is often the real question. Aesthetic standards may be applied to the accessory unit only if the town also applies them to the main house.

The 750 and 950 square foot rules, and three cities

The statute gives a ceiling and a floor. The total living space of an accessory unit shall not exceed 950 square feet unless the municipality authorizes more, and a municipality may not restrict it to less than 750 square feet. Cities then set their own figure inside that. Nashua's ordinance, amended in December 2025, allows 980 square feet. Manchester's land use code, in effect from 1 March 2026, allows an accessory unit as a standalone structure with a 950 square foot limit. Concord's ordinance, adopted in October 2025, says an accessory unit may be attached or detached and that manufactured housing shall not be used as one.

The building code: the 2024 edition, and a 600 square foot tiny house

The state building code now adopts the 2024 International Residential Code under RSA 155-A:1, effective 1 July 2026, and the State Fire Marshal's office says permits may use the 2021 or the 2024 editions through 31 December 2026. New Hampshire adopted the code's tiny house appendix with one change that matters for a small home: the Building Code Review Board's amendment summary raises the definition of a tiny house from 400 to 600 square feet of habitable space, excluding lofts. That appendix is what relaxes ceiling heights, lofts and stairs, so here it reaches a larger home than the model code does.

A tiny house on wheels

The accessory dwelling unit law is written for a dwelling unit on a lot containing a single-family home, with its own sleeping, eating, cooking and sanitation, and the route that carries its rights is a permitted building. We found no New Hampshire statute that classifies a tiny house on wheels as one, and local rules can be strict: Nashua's code limits a guest camper to 30 days a year. Ask your town how it treats a home on wheels before buying one for a backyard.

The national version of this question explains why the wheels-or-foundation split comes first in every state, and the New Hampshire guide carries snow load, frost depth and the code in force with a source for each.

02 — Where to go next

The New Hampshire state guide The same question for the whole US Granny pod laws by state Building codes, state by state How certification works

03 — Sources

Each figure above links to the authority it came from.

RSA 674:72 (2025, 197:2, eff. July 1, 2025; 2026, 210:2, eff. Aug. 31, 2026): a municipality shall allow accessory dwelling units in all zoning districts that permit single-family dwellings; one accessory dwelling unit, attached or detached, shall be allowed as a matter of right, without additional requirements for lot size, setbacks, aesthetic requirements, design review, frontage or space limitations; up to one additional parking space (IV); adequate water supply and sewage disposal (V); owner occupancy of one unit may be required but not which unit (VI); total living space shall not exceed 950 square feet unless otherwise authorized by the municipality and may not be restricted to less than 750 square feet (VII); no familial relationship requirement (VIII); no one-bedroom limit (IX); no denial of a separate electrical panel and service (XII)
gc.nh.gov
RSA 674:73 (2025, 197:3, eff. July 1, 2025): a municipality shall permit one detached accessory dwelling unit
gc.nh.gov
RSA 674:71: an accessory dwelling unit is a residential living unit on a lot containing a single-family dwelling that provides independent living facilities including sleeping, eating, cooking and sanitation; attached and detached units are defined separately
gc.nh.gov
RSA 155-A:1: the state building code adopts the International Residential Code 2024 (2025, 276:2, eff. July 1, 2026)
gc.nh.gov
New Hampshire State Fire Marshal, State Building Code: permits may use the 2021 or the 2024 editions through December 31, 2026, and the 2024 editions only from January 1, 2027
firemarshal.dos.nh.gov
New Hampshire Building Code Review Board, state building code amendments summary, July 1, 2026: adopts International Residential Code Appendix BB, Tiny Houses, and amends BB102.1 so that a tiny house is a dwelling of 600 square feet or less of habitable space excluding lofts (RE-24-01-25)
mm.nh.gov
City of Nashua Land Use Code section 190-32, amended December 23, 2025 (O-25-076): accessory dwelling unit of up to 980 square feet. Section 190-35: a guest camper is limited to 30 days a year
ecode360.com
City of Manchester Land Use Code, ordained December 16, 2025, effective March 1, 2026, section 4.6.1.A: an accessory dwelling unit is allowed as a standalone structure with a 950 square foot limit
manchesternh.gov
City of Concord Zoning Ordinance section 28-5-52 (Ord. 3186, adopted October 14, 2025): accessory dwelling units may be either attached or detached; manufactured housing shall not be used as accessory dwelling units
library.municode.com

04 — Related questions

Can you put a tiny house in your backyard in the US?Which US states let you build a granny pod as of right?What is a prefab ADU?Can you put a tiny house in your backyard in Washington state?Are tiny homes legal in Kansas, and where can you put one?

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