HB577
Sponsored By: Joe H. Alexander (Republican)
Signed by Governor
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Bill Overview
Analyzed Economic Effects
6 provisions identified: 3 benefits, 1 costs, 2 mixed.
Convert garages and sheds to ADUs
Starting July 1, 2025, towns must allow you to convert existing structures, like detached garages, into ADUs. This applies even if the structure now violates setback or lot‑coverage limits.
One ADU allowed statewide, including detached
Beginning July 1, 2025, every town must allow one accessory dwelling unit (ADU) in any zone that allows single‑family homes. Towns cannot add extra rules like bigger lot size, added frontage, or special design review beyond what applies to a single‑family home. If a town has no ADU rules, one ADU is allowed by right and you only need the usual building permits required by law. Detached ADUs are also allowed and must follow RSA 674:72, IV–IX and any local rules made under that law. The law defines what counts as an ADU, including attached and detached units.
ADUs can count as workforce housing
Starting July 1, 2025, an ADU can count toward a town’s workforce‑housing obligation if it meets the rental rules in RSA 674:58, IV. This helps towns meet housing goals and can encourage more rental ADUs.
Limits on ADU sales and owner occupancy
Starting July 1, 2025, you cannot sell an ADU as a separate condo from the main house unless your town allows it. Towns may prohibit ADUs for attached homes like townhouses and on rented or leased land. A town may require the owner to live in one of the two units and can require proof, but it cannot choose which unit. Only one ADU is allowed per single‑family home.
ADU size, design, and parking rules
Beginning July 1, 2025, towns must apply the same rules to a home with an ADU as to other single‑family homes and cannot make them stricter. ADU size cannot be capped below 750 square feet; the default cap is 950 square feet unless a town allows larger. Any look or style rules must match those for the main house. An attached ADU may use its own entrance or a shared common space; towns cannot force one option. If a town requires parking for the main house, it may require up to one extra space per ADU, either on‑site or at a legal off‑site spot. Towns cannot limit an ADU to one bedroom or require ADU occupants to be related to people in the main house. Towns cannot block a separate electric panel or separate service for the ADU.
Water and sewer rules for ADUs
Beginning July 1, 2025, ADU applicants must show adequate water supply and sewage disposal under RSA 485‑A:38. You must submit a sewage system approval application before construction, and install an approved system if the existing one lacks approval, fails, or needs replacement. Separate water or sewage systems for the ADU and the main house are not required.
Sponsors & Cosponsors
Sponsor
Joe H. Alexander
Republican • House
Cosponsors
Alissandra Murray
Democratic • House
Dan McGuire
Republican • House
Daniel E. Innis
Republican • Senate
Hope E Damon
Democratic • House
Jessica Grill
Democratic • House
Joe Sweeney
Republican • House
Keith R. Murphy
Republican • Senate
Lisa R Mazur
Republican • House
Roll Call Votes
No roll call votes available for this bill.
Actions Timeline
Signed by Governor Ayotte 07/15/2025; Chapter 197; eff. 07/01/2025 HJ 18
7/22/2025HouseEnrolled Adopted, VV, (In recess 06/26/2025); SJ 18
7/2/2025SenateEnrolled (in recess of) 06/26/2025 HJ 18 P. 59
7/2/2025HouseEnrolled Bill Amendment # 2025-2874e: AA VV (in recess of) 06/26/2025 HJ 18 P. 57
6/27/2025HouseEnrolled Bill Amendment # 2025-2874e Adopted, VV, (In recess of 06/26/2025); SJ 18
6/27/2025SenateOught to Pass: MA, VV; OT3rdg; 05/15/2025; SJ 13
5/15/2025SenateSen. Fenton Floor Amendment # 2025-2162s, AF, VV; 05/15/2025; SJ 13
5/15/2025SenateCommittee Report: Ought to Pass, 05/15/2025, Vote 5-1; SC 21A
5/13/2025SenateHearing: 03/25/2025, Room 100, SH, 10:45 am; SC 14
3/18/2025SenateIntroduced 03/06/2025 and Referred to Commerce; SJ 7
3/11/2025SenateOught to Pass with Amendment 2025-0449h: MA VV 03/06/2025 HJ 7 P. 15
3/6/2025HouseAmendment # 2025-0449h: AA VV 03/06/2025 HJ 7 P. 15
3/6/2025HouseCommittee Report: Ought to Pass with Amendment # 2025-0449h 02/18/2025 (Vote 18-0; CC) HC 14 P. 10
2/26/2025HouseExecutive Session: 02/11/2025 10:00 am LOB 305
2/26/2025HouseFull Committee Work Session: 02/11/2025 10:00 am LOB 305
2/5/2025HousePublic Hearing: 02/04/2025 10:00 am LOB 305
1/29/2025HouseIntroduced (in recess of) 01/09/2025 and referred to Housing HJ 3 P. 17
1/16/2025House
Bill Text
As Amended
6/27/2025
Enrolled
6/27/2025
Introduced
1/16/2025
CHAPTERED FINAL VERSION
Version adopted by both bodies
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