ADU rules in Laconia

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. Both the special exception gate and that definitional limit are in conflict with state law: RSA 674:73, as amended by 2025 NH 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, attached or detached, to be allowed 'as a matter of right.'

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 § 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. § 235-41A(7) adds that 'An interior door must be provided between the principal dwelling unit and the accessory dwelling unit, if attached.' That requirement now sits badly with state law: ch. 197 repealed and reenacted RSA 674:72 in full, and the reenacted paragraph III says an attached ADU shall have either an independent means of ingress and egress or ingress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.

§ 235-41A(8) sets the range: 'The ADU must not be less than 300 square feet, and must not exceed 1,000 square feet. If the principal dwelling unit is greater than 4,000 square feet, the ADU must not exceed 25% of the gross living area of the principal dwelling unit.' Because 25% of anything over 4,000 square feet is more than 1,000, that second sentence reads as a bonus for large houses rather than an extra squeeze. Laconia's 1,000 square feet is more generous than the state default: RSA 674:72, VII caps an ADU at 950 square feet 'unless otherwise authorized by the municipality' and bars any municipality from restricting the unit below 750 square feet. There is no ADU-specific height limit; Table II sets maximum structure height at 35 feet in RR1, RR2, RS, SFR, RG and CR and 60 feet in RA, C and UC, and § 235-41A(4) requires a new detached structure to meet the district's setbacks (for example 25 feet front, 10 feet side and 15 feet rear in RS and SFR). § 235-41A(2) keeps the ADU from counting against minimum lot size or residential density, which matters on Laconia's 10,000 square foot serviced lots.

Laconia requires it and, unlike the special exception gate, this condition survives the 2025 state law intact. § 235-41A opens 'One ADU is permitted on any owner-occupied single-family dwelling,' § 235-41A(1) repeats that an ADU 'is permitted only on properties containing an owner-occupied single-family dwelling,' and § 235-41A(3) makes it an ongoing documented duty: 'The property owner must occupy either the principal dwelling unit or the ADU as their primary residence. The owner must provide documentation demonstrating to the satisfaction of the City that one of the units is their primary residence.' The ordinance does not dictate which unit, which matters because RSA 674:72, VI allows a municipality to require owner occupancy of one of the dwelling units but expressly forbids it from specifying which, and permits the municipality to demand proof of principal residence and to adopt reasonable enforcement regulations. Practical consequence: only one of the two units can ever be leased.

§ 235-41A(11) requires 'at least one off-street parking space for the ADU in addition to the off-street parking requirements for the principal dwelling unit,' and Table III (235 Attachment 4) sets a single-family dwelling at 2 spaces, so the working answer is three spaces on the lot. Table III also carries a separate line, 'Single-family with accessory apartment, 2, Dwelling unit,' which could be misread as 2 spaces per unit and therefore 4 total; that table has not been amended since 2001 and the specific, recently amended § 235-41A(11) controls. RSA 674:72, IV independently caps the city at 'up to one additional parking space for each accessory dwelling unit,' so a four-space demand would not be lawful. Each space must be at least 9 feet by 19 feet (§ 235-47A). Inside the Commercial Core Parking Overlay District no off-street parking is required at all (§ 235-45B(1)). One conflict worth knowing: RSA 674:72, IV lets required spaces sit 'either on-site or at a legally dedicated off-site location, at the property owner's discretion,' while § 235-45D(3) requires a Planning Board conditional use permit before parking may go off-site.

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. The city's own short-term lodging application still describes an ADU as one 'created by the granting of a Special Exception by the Zoning Board of Adjustment,' which is good evidence this is the live practice. 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.

The headline rule is the trade-off in § 235-41A(14): 'Any lot with an approved ADU is not permitted to use short-term lodging. Any lot approved for short-term lodging is not permitted to have an ADU,' and taking a permit for one rescinds every prior permit for the other. § 235-41M(3)(a) says the same thing from the other side, requiring a short-term lodging unit to be 'a single-family home with no accessory dwelling unit,' and the § 235-41M preamble excludes the rental or occupancy of a residential accessory dwelling unit from the short-term lodging use entirely. That is a real cost in a Lakes Region market: short-term lodging (defined in § 235-13 as stays of one to 14 consecutive nights) is permitted by right in the Commercial Resort and Shorefront Residential districts and by special exception in RR1, RR2, RG, RA, UC and C, where it is capped at 120 days a year, limited to the owner's primary residence and subject to an annual report to the Planning Department. Long-term renting is otherwise unregulated: Laconia has no rental registration or licensing scheme (Chapter 155 adopts the BOCA National Property Maintenance Code/1996 and nothing more), but owner occupancy of one of the two units under § 235-41A(1) and (3) means only one unit can be leased at a time. § 235-41A(12) forbids converting the structure and lot 'to a condominium or any other form of legal ownership distinct from the ownership of the principal dwelling unit,' which tracks the separate-conveyance bar in RSA 674:72, I.