ADU rules in Richland County

Unincorporated Richland County lists 'Accessory dwelling unit' as permitted by right (P) in Table 26-4.3(c) in the AG, HM, RT and R1 through R6 districts and in the CC-1 to CC-3 Crane Creek districts, and as allowed under an approved plan in PD and PD-TND. The Land Development Code defines an ADU as a secondary unit with its own kitchen, bathroom and sleeping area 'either within the same structure, or on the same lot' as the primary dwelling, so a detached backyard unit qualifies. The lot must hold one single-family detached dwelling, only one ADU is allowed, and a manufactured home cannot serve as the ADU. It is not allowed in the open space, mixed-use, commercial or industrial districts.

The same use row covers an ADU inside or attached to the house: the definition says the unit may exist 'within the same structure' as the primary dwelling, and Sec. 26-4.3(d)(1)c only requires that an internal or attached unit not alter the house 'so as to appear to contain more than one dwelling unit'. It is permitted by right in AG, HM, RT, R1 through R6 and CC-1 to CC-3, with one ADU per single-family dwelling.

Sec. 26-4.3(d)(1)e caps the ADU at 750 square feet or one-fourth of the principal dwelling's heated floor area, 'whichever is greater', so a 4,000 square foot house supports a 1,000 square foot ADU. A detached ADU is an accessory structure, and in Residential districts all accessory structures together may not exceed 50 percent of the principal building's gross floor area or 1,200 square feet, whichever is greater, nor cover more than 30 percent of the rear yard (RT lots of two acres or more get 2,500 square feet). Accessory structures may be as tall as the district allows for principal buildings, must stay behind the front building line, meet the side setback, and sit at least five feet from rear property lines. For density purposes an ADU does not count as a dwelling unit.

Neither the ADU standards in Sec. 26-4.3(d)(1)a-e nor the definition requires the owner to live in either unit, at application or afterward. Owner residence matters only for short-term rental uses (hosted home-based lodging must be the operator's primary residence) and for the county's separate rental registration, which applies to non-owner-occupied units.

Table 26-5.2(d)(1) sets minimum parking by principal use only; it requires 2 spaces per single-family detached dwelling and has no row for an accessory dwelling unit, and the ADU standards in Sec. 26-4.3(d)(1) add no parking rule. A short-term rental changes this: hosted home-based lodging needs one extra space for lodgers, and Chapter 16's short-term rental article requires two designated spaces per rental property.

A 'P' in Table 26-4.3(c) means the ADU is 'allowed by right' subject only to the use-specific standards, and Sec. 26-4.3(b)(1) treats accessory uses as permitted uses. The route is a building permit plus the Zoning Administrator's certificate of zoning compliance before occupancy (Sec. 26-2.5(n)), with no hearing; appeals of that decision go to the Board of Zoning Appeals. In PD and PD-TND districts the ADU must be listed in the approved PD Plan and PD Agreement.

The zoning code places no rental or separate-sale rule on the ADU itself. Under Code Sec. 16-72 the owner of any non-owner-occupied habitable residential unit must register it in the county's online database within 30 days, and an owner of more than one long-term rental needs a business license. Short-term rental (under 30 days) of any residential property, owner-occupied or not, requires a business license, a responsible local representative within 45 miles, two designated parking spaces and an occupancy cap of two persons per bedroom plus two (Secs. 16-80 to 16-82, Ord. 007-24HR, 4-9-2024). Under the LDC, 'home-based lodging' (a whole dwelling for transient occupancy) is a principal use permitted with special requirements in AG, HM, RT and R1 but not R2 to R6, while 'home-based lodging, hosted' (in the operator's primary residence, one rental contract per night, at most six adult lodgers) is permitted in AG, HM, RT and R1 through R6.