ADU rules in Cumberland

Cumberland allows one ADU per lot by right only in the three state circumstances, which Ord. No. 25-21 (adopted December 3, 2025) copied into § 6-6(a): a disability accommodation on an owner-occupied property, a lot of 20,000 sq ft or more in residential use, or a unit inside the existing footprint of the house or an existing attached or detached accessory structure. A new detached ADU building therefore needs a lot of at least 20,000 sq ft; on smaller lots a detached ADU is possible only by converting an existing garage or shed without expanding it. Sewered R-2 and R-3 lots start at 10,000 sq ft, so the gate bites in most of the built-up town. The Use Table lists ADUs (use 9B) as allowed in the A-1, A-2, R-1, R-2 and R-3 zones and prohibited in commercial, industrial and open space zones. Under the directory's Rhode Island convention a town whose only by-right path is the three statutory circumstances is recorded as conditional.

An internal conversion (basement, attic or other space within the existing footprint of the house) is allowed by right on any qualifying residential lot under § 6-6(a)(3), and legal nonconforming structures need no zoning relief for a within-footprint ADU (§ 6-6(i)). An ADU built as an addition that expands the footprint is by right only on a lot of 20,000 sq ft or more (§ 6-6(a)(2)) or as an owner-occupied disability accommodation (§ 6-6(a)(1)). The ordinance provides no special use permit path for ADUs outside these circumstances, so an expanding addition on a smaller lot has no listed route short of zoning relief.

§ 6-6(g) caps an ADU at 60 percent of the principal dwelling's floor area or 900 sq ft for a studio or one-bedroom unit and 1,200 sq ft for a two-bedroom unit, whichever is less, which is exactly the state minimum in § 45-24-73(b)(1). Ord. No. 25-21 raised the cap from 50 percent and 800 sq ft of living area. An ADU may have up to two bedrooms (§ 6-6(d)). A detached ADU in an accessory building is also subject to § 6-5(c), which limits any accessory building to 936 sq ft or 60 percent of the principal structure, whichever is less, and § 6-5(b), one or two stories and no more than 20 ft; that accessory building cap can hold a two-bedroom detached unit below the 1,200 sq ft state floor.

Ord. No. 25-21 deleted the former rule that 'the owner of the property must reside in either the principal dwelling or the ADU' along with the family-member declaration recorded in the land evidence records. Owner occupancy now appears only in the disability-accommodation circumstance of § 6-6(a)(1) ('on an owner-occupied property'), matching § 45-24-73(a)(1). ADUs allowed on 20,000 sq ft lots or within an existing footprint carry no owner-occupancy requirement. A leftover clause, § 4-7(e) (Ord. No. 23-26), still speaks of an ADU 'in an owner-occupied residence' as a reasonable accommodation for family members; it frames an additional accommodation route rather than a condition on § 6-6 ADUs.

§ 6-6(e) sets 'the minimum number of off-street parking spaces required for an ADU' at one per bedroom, so a studio or one-bedroom ADU needs one space and a two-bedroom ADU two. That is the highest requirement § 45-24-73(b)(2)(viii) permits. Ord. No. 25-21 changed the prior flat one-space rule to the per-bedroom count. A driveway may count as a required space for a detached single- or two-family dwelling under § 14-2(a).

§ 6-6(a) makes one ADU per lot 'permitted by right' in each of the three circumstances, and § 45-24-37(e) requires those ADUs to go through an administrative building permit process only. Cumberland lists no special use permit category for ADUs in § 18-3 or the Use Table (use 9B is 'Y' in the A and R zones), so every ADU the ordinance allows is ministerial. An ADU outside the three circumstances (a new detached unit or expanding addition on a lot under 20,000 sq ft) has no listed path and would need zoning relief from the Zoning Board of Review; § 45-24-73(b)(3) bars reviewing such an application as a land development project by itself.

§ 6-6(j) repeats the state bar: 'The ADU shall not be offered or rented for tourist or transient use or through a hosting platform, as such term is defined in R.I.G.L. § 42-63.1-2' (stays under 30 consecutive days). Ord. No. 25-21 struck the old accessory family dwelling unit regime, which limited occupancy to family members with disabilities or aged 62 and older, required a recorded declaration and ended the unit when they left or title transferred; nothing in § 6-6 now restricts who may rent the ADU long term. Cumberland's Use Table lists 'Group quarters, short-term rentals and lodging' (use 13, defined as a rooming house of ten rooms or less) as prohibited in every district, and the code has no separate short-term rental registration chapter.