ADU rules in Smithfield

Smithfield's Table of Uses lists Accessory Dwelling Unit as permitted by right (P) in the R-200, R-80, R-Med, R-20 and R-20M residential districts and the MU Mixed Use district, with no lot-size or footprint gate. The town's definition (Sec. 2.2(2) and 4.4.B-1) copies the state definition and expressly includes a detached unit or a unit in an accessory structure such as a detached garage. One ADU is allowed per single-family or multifamily dwelling. A detached ADU follows the accessory-building rules of Sec. 6.2.1 (no front yard, 20 ft height cap, 10 ft from the principal building, 15 ft side and rear setbacks in R-200, R-80 and R-Med, 10 ft in R-20 and MU).

The same by-right listing covers attached and internal units: the definition includes 'a unit that is part of an expanded or remodeled primary dwelling,' so footprint-expanding additions are by right where they meet the district's dimensional rules. An ADU inside a single-family house should, 'to extent practicable,' keep the appearance of a one-family residence. Additions that break setbacks still need a dimensional variance (the Zoning Board of Review heard one such request for an attached ADU in R-20 on 11-5-2025).

Sec. 4.4.B-1.B sets a minimum of 400 sq ft and a maximum of 800 sq ft of interior floor area for every ADU, with no bedroom-based split. R.I. Gen. Laws 45-24-73(b)(1) requires towns to allow at least 900 sq ft or 60 percent of the principal dwelling's floor area (whichever is less) for a studio or one-bedroom ADU and at least 1,200 sq ft or 60 percent for a two-bedroom ADU. The 800 sq ft cap therefore falls short of the state floor whenever the principal dwelling exceeds about 1,333 sq ft; in that case the statute controls and a one-bedroom ADU of up to 900 sq ft (two-bedroom up to 1,200 sq ft), capped at 60 percent of the house, must be allowed. Detached units also follow the 20 ft accessory-building height cap.

Smithfield's ADU provisions (Sec. 2.2(2), 4.3 and 4.4.B-1) contain no owner-occupancy requirement, at application or afterward. The former familial-relationship condition is gone: Sec. 4.4.B-1.F says ADUs approved with a family-occupancy condition are not nonconforming for lacking that relationship because amendments to state law and the ordinance removed it. State law imposes owner occupancy only for the disability-accommodation circumstance of 45-24-73(a)(1).

Sec. 4.4.B-1.E requires a lot with an ADU to provide one parking space beyond what Sec. 7.4(A) requires for the principal dwelling (two spaces per unit for one- and two-family dwellings, plus one per bedroom over three). One space is within the state cap of 45-24-73(b)(2)(viii), which bars requiring more than one space per ADU bedroom.

ADUs are a by-right (P) use in every district where the table allows them, so no special use permit or Planning Board review applies; an ADU that meets Sec. 4.4.B-1 and the dimensional rules goes through a building permit. The state reaches the same result for qualifying ADUs under 45-24-37(e), which requires an administrative building permit process only. Proposals needing setback or other dimensional relief go to the Zoning Board of Review for a variance.

R.I. Gen. Laws 45-24-73(b)(8) bars offering or renting any ADU for tourist or transient use (under 30 consecutive days) or through a hosting platform. Smithfield's ordinance adds no rental rule of its own: it no longer requires a family relationship between the occupants (Sec. 4.4.B-1.F), and state law (45-24-73(b)(2)(i)) bars familial or age tenant restrictions anyway. Smithfield has no short-term rental chapter in its Code of Ordinances or use category in its zoning ordinance; the Planning Board discussed a new short-term rental use category on 1-16-2025, but no adopted amendment appears on the town's ordinance page.