Compare ADU rules across New Hampshire

A detached ADU is contemplated by the ordinance but is gated behind a discretionary hearing. § 235-41A(4) provides that an ADU 'may be located in the same building as the principal dwelling unit or in a separate detached structure such as a garage or barn,' with any new structure meeting the district's dimensional standards. Table I (235 Attachment 2) then marks 'Accessory dwelling unit' as E, special exception, in every district that permits a single-family dwelling: RR1, RR2, RS, SFR, RG, RA, CR, UC and C; it is N, not permitted, in the Industrial Park, Industrial and Airport Industrial districts, which do not allow single-family dwellings either. A second local wrinkle is that the § 235-13 definition is narrower than § 235-41A(4): it describes an ADU as a unit 'within or attached to a single-family dwelling, or located in a legally existing accessory structure on the same lot,' which read literally would allow a garage or barn conversion but not a newly built backyard cottage. Laconia never copied the statutory definitions of attached and detached units, so the reclassification worked by 2026 NH Laws ch. 210 (HB 1079), in force since August 31, 2026, changed nothing here: a unit inside a converted garage or barn was already detached under § 235-41A(4) and is now detached under state law too. Both the special exception gate and the definitional limit conflict with state law: RSA 674:73, as amended by 2025 NH Laws ch. 197 (HB 577) effective July 1, 2025, reads 'A municipality shall permit one detached accessory dwelling unit,' and RSA 674:72, I requires one ADU, attached or detached, to be allowed 'as a matter of right.'

Ordinance read September 2026

An attached or internal ADU runs the same special exception gauntlet: Table I gives 'Accessory dwelling unit' a single E rating that covers both forms, so a basement, attic or addition conversion needs the same Zoning Board of Adjustment approval as a detached unit. § 235-41A(4) allows the ADU 'in the same building as the principal dwelling unit,' and only two conditions turn on the attached-versus-detached line: § 235-41A(5) requires an ADU built into an addition to share the existing dwelling's utilities (telephone and television excepted) while a detached unit may take separate municipal water and sewer connections, and § 235-41A(7) adds that 'An interior door must be provided between the principal dwelling unit and the accessory dwelling unit, if attached.' Both tests are about physical attachment rather than the state definitions, so 2026 NH Laws ch. 210's move of preexisting-detached-structure units onto the detached side has no local consequence. The interior-door rule sits badly with state law: ch. 197 repealed and reenacted RSA 674:72 in full, and the reenacted paragraph III says an attached ADU shall have either an independent means of ingress and egress or ingress and egress through a shared common space and that 'the municipality shall not limit the choice of ingress and egress.' The owner-occupancy condition, the 1,000 square foot cap and the extra parking space apply identically to an attached unit.

Ordinance read September 2026

As Laconia's ordinance is written, an ADU needs a special exception from the Zoning Board of Adjustment in every district where it is allowed. Table I rates 'Accessory dwelling unit' as E citywide, § 235-26 defines E as permitted by special exception, and § 235-70C(1) gives the ZBA the power to hear and decide special exceptions 'specifically authorized in the Table of Permitted Uses.' That means a noticed public hearing with certified-mail abutter notice at least five days out (§ 235-69C(3)), eight written findings including that the use 'will not create hazards to the health, safety, or general welfare of the public, not be detrimental to the use of or out of character with the adjacent neighborhood' (§ 235-70C(2)), a concurring vote of three members (§ 235-69C(5)), and the ZBA's power to attach conditions (§ 235-70C(4)). The zoning and planning fee schedule adopted 2-10-2020 charges $125 for zoning applications plus abutter notice costs. On top of that, § 235-41A(13) requires an application approved by the Planning Department, a building permit for all construction, and a certificate of occupancy before occupancy. Since July 1, 2025, however, RSA 674:72, I has required one ADU to be allowed 'as a matter of right' and barred 'other controls beyond what would be required for a single-family dwelling without an accessory dwelling unit,' so the special exception requirement is preempted; Laconia amended § 235-41 and Table I on 9-8-2025 and again on 3-9-2026 without changing it. Which path the counter actually applies is untested: no ADU case appeared on any Zoning Board of Adjustment agenda from January through August 2026, and the city document that described an ADU as one 'allowed by a Special Exception granted by vote of the Zoning Board of Adjustment' was the December 2019 short-term lodging handout, which the city replaced on 8-13-2026 with the current ordinance text. Ask the Planning Department which path it uses and be ready to cite RSA 674:72, I in writing.

Ordinance read September 2026

Rochester's own ordinance still sends every detached unit to the Zoning Board of Adjustment. Section 275-23.2A(1)(a) allows an accessory apartment where the Tables of Uses permit it, then adds that "if the accessory dwelling is detached from the single-family dwelling, it must be approved by a special exception," and (b) requires a detached unit to be "similar in architectural style" to the house. That is the 2017 text and it predates New Hampshire's rewrite: RSA 674:73, as amended by 2025 Laws ch. 197 (HB 577, effective July 1, 2025), now reads "A municipality shall permit one detached accessory dwelling unit," and RSA 674:72, I requires one ADU, "which may be either attached or detached," to be allowed "as a matter of right" in every district that permits single-family dwellings, with no added controls for lot size, setbacks, aesthetics, design review, frontage, or space limitations, so both the special-exception step and the architectural-style condition are preempted. Since August 31, 2026 the conflict clearly covers conversions too: 2026 Laws ch. 210 (HB 1079) rewrote RSA 674:71, III so a unit completely contained within a preexisting detached structure is a detached unit, which is how Rochester has always drawn the line anyway (its trigger is physical detachment from the house, not the statutory definition), so a garage or barn conversion is a detached unit under both texts and RSA 674:73 plus the conversion mandate in RSA 674:72, XI reach it squarely. Rochester has not conformed Chapter 275: the eCode360 text is still codified through 10-07-2025 and no ADU amendment appeared on a Planning Board, Codes and Ordinances Committee, or City Council agenda between April 2026 and September 3, 2026. Treat a detached backyard unit as lawful as of right under the statute, but expect the counter to point at the special-exception track until the city amends.

Ordinance read September 2026

An attached or internal unit (a basement, an addition, or space over a garage that is attached to the house) is the mainstream path, but the district matters. Table 18-A lists "Apartment, accessory (accessory use)" as permitted by right in Residential-2, Agricultural, Neighborhood Mixed-Use, Downtown Commercial, Office Commercial, and Highway Commercial, and as a special exception in Residential-1 and Hospital Special; it is not allowed in General Industrial, Recycling Industrial, or Airport Special. So R2, the dense older neighborhoods, can add one over the counter, while R1, the lower-density single-family district with a 10,000 sq ft minimum lot, still requires a Zoning Board hearing under the unamended table. Section 275-23.2A(1)(b) limits the use to single-family dwellings only, (f) allows just one per lot, and (e) requires an interior door between the two units when the accessory apartment is inside the house. RSA 674:72, I now requires as-of-right treatment in every district that permits single-family dwellings, which in Rochester means R1, R2, AG, NMU, OC, HC, and HS, so the R1 and HS special-exception entries are preempted; the 2025 reenactment also dropped the old statutory permission to require an interior door and added that a municipality "shall not limit the choice of ingress and egress" (RSA 674:72, III). Since August 31, 2026 RSA 674:71, II defines an attached unit as one "within or attached to the principal dwelling unit" and nothing more, so a unit inside a freestanding garage or barn is no longer an attached unit under state law; for that project read the detached row.

Ordinance read September 2026

It depends on the unit type and the district. An attached accessory apartment in R2, AG, NMU, DC, OC, or HC is administrative: Section 275-23.2A(1)(j) exempts it from site plan review and asks only that "a letter of intent must be submitted to the Building Inspector to ensure that the above conditions are met," alongside the building permit Section 275-3.3A requires from the Director of Building, Zoning, and Licensing Services and the certificate of occupancy under Section 275-3.3E. Any detached unit, which since August 31, 2026 includes a unit inside a preexisting detached garage or barn under RSA 674:71, III, and any accessory apartment in the R1 or Hospital Special district, goes to the Zoning Board of Adjustment for a special exception under Article 22, meaning a noticed public hearing, the base criteria in Section 275-22.2, and the Board's power under Section 275-22.1G to impose "such additional conditions as it finds reasonably appropriate," including increased setbacks and screening. RSA 674:72, I as reenacted in 2025 makes one ADU allowable as a matter of right with no controls beyond those for a single-family dwelling, so the special-exception track is preempted in substance, but it is what the ordinance on the books prescribes and what the ZBA docket still reflects in 2026. Rochester publishes no ADU-specific application form: the Planning and Development forms library (39 forms, inventoried September 6, 2026) offers only the generic Special Exception Application and Variance Package. One genuine local benefit: Section 275-27.3G(5) waives impact fees for accessory dwelling units.

Ordinance read September 2026