ADU rules in Tulsa County

A detached ADU is allowed by right on any lot occupied by a single detached house in the AG, AG-R, RE, RS-1, RS-2, RS-3, RD, RM and RMH districts of unincorporated Tulsa County, one per lot. It may be newly built beside an existing house, built together with a new house, or created by converting space inside an existing detached accessory building. The building holding the ADU must sit at least 10 feet behind the rear wall of the house (or 10 feet behind the front building line where the ADU is allowed beside the house), and a detached ADU in the rear setback also follows the accessory-building rules of Sec. 8.030. The RT (townhouse) district is not on the list.

Interior conversions (an attic or basement, for example) and additions that add floor area to an existing house are both listed methods of creating an ADU, as is building a new house with an internal ADU; they are allowed by right in the same districts as detached units (AG, AG-R, RE, RS, RD, RM, RMH) on lots with a single detached house. The Chapter 19 definition still describes an ADU as a unit 'located in an accessory building', but Sec. 8.040, which applies 'to all accessory dwelling units', expressly authorizes the internal and addition methods.

The cap is the GREATER of 750 square feet or 40 percent of the principal dwelling's floor area, so a 2,500 square foot house can have a 1,000 square foot ADU. No extra lot area per unit or open space is required for the ADU. Detached ADUs located within rear setbacks are also subject to Sec. 8.030 and Table 8-1: combined accessory-building coverage of 25 percent of the lot (the table's coverage row), a height limit of 18 feet on lots of 22,500 square feet or less and 25 feet on lots of 22,501 to 43,560 square feet (no maximum on larger lots), and 3-foot side and rear setbacks on smaller lots (the principal building's setbacks on lots over 1 acre).

Neither Sec. 8.040 nor any other provision of the 2024 regulations (definitions included) requires the owner to live in either unit; the ADU section regulates location, number, method, size, entrances and setbacks only. Oklahoma has no state ADU statute, so this is purely the county's choice. The owner-residence idea appears only in the short-term rental rules (an accessory short-term rental must be in a household's primary residence), not as an ADU condition.

Table 10-1 has no ADU row, and Sec. 10.040-B exempts accessory buildings from the minimum off-street ratios of Table 10-1, which covers a detached ADU in an accessory building. An internal or attached ADU is not addressed expressly: the house itself needs 2 spaces ('Single-unit living, 2 per dwelling unit'), and for unlisted uses the county inspector may apply the most similar listed ratio under Sec. 10.030-F, so an inspector could ask for spaces for an attached unit. Most unincorporated lots are large, so this rarely bites in practice.

ADUs are 'allowed by right' in the listed districts, so a compliant unit needs only the county's ordinary building permit and zoning review by the county inspector, with no public hearing. Departures go to the Tulsa County Board of Adjustment: a side-yard detached ADU needed a variance of Sec. 8.030 (CBOA-3373, approved 7-21-2026), and a second ADU on an AG lot needed lot-area variances for a third dwelling (CBOA-3331, approved 4-21-2026). At the July hearing county staff stated that a rear-yard ADU 'would be a use by right'.

The regulations put no rental limit on an ADU, and household living expressly includes dwelling units rented month-to-month or longer. Short-term rentals are a permitted (P) lodging use in AG, AG-R and every R district, subject to Sec. 7.150 (a unit that is not a household's primary residence) or Sec. 8.170 (renting all or part of a primary residence as an accessory use): stays of no more than 29 consecutive days, no more than 8 occupants including residents, a guest register available to code enforcement, no on-site events, and no commercial-looking site changes. No county short-term rental license or registration appears in the regulations; Oklahoma has no state short-term rental preemption, and lodging taxes apply under state law. The county Board of Adjustment approved a second ADU in April 2026 that the owner said would be a rental.