Cobb County is bringing back its accessory dwelling unit proposal and introducing the county's first data center regulations. East Cobb residents will get their chance to weigh in at three public hearings in October before commissioners vote.

The Cobb Board of Commissioners will hear both proposals at a work session Tuesday, Sept. 22, beginning at 1:30 p.m., East Cobb News reported. No votes will be taken. Commissioners will hold public hearings on Oct. 13 at 9 a.m. and Oct. 27 at 7 p.m. at 100 Cherokee Street in Marietta. A vote is expected to follow the Oct. 27 hearing.

The Cobb Planning Commission will also hold a hearing on Oct. 6 at 9 a.m., according to the Marietta Daily Journal.

Accessory dwelling unit proposal returns

Commissioners withdrew a nearly identical ADU proposal on Nov. 12, 2024, after vocal citizen opposition. The Cobb Planning Commission had voted to deny approval, and single-family neighborhoods raised concerns about density and enforcement.

The revived language would cap accessory dwelling units at 850 square feet or half the primary home's square footage, whichever is smaller. Units could be no taller than one story and must sit behind the primary residence. Property owners would have to live in either the main home or the ADU, and short-term rentals would be banned. Each single-family lot would be limited to one ADU with at least one off-street parking space.

Two commissioners have already signaled skepticism. Commissioner Keli Gambrill told the Marietta Daily Journal on Sept. 9 that ADUs would crowd neighborhoods and strain parking without meaningfully addressing affordable housing. District 3 Commissioner JoAnn Birrell, who represents East Cobb, said in the same report that she does not plan to support the proposal, citing enforcement and setback concerns.

"I'd like to hear from the public what they think, but right now I do not support it," Birrell said at the time.

Acworth, Mableton, Marietta and Powder Springs already allow ADUs. Unincorporated Cobb does not.

Data center rules take shape

The county has been operating under a data center moratorium since the board voted unanimously on Aug. 11 to extend it through Feb. 24, 2027. Cobb's 1972 county code has no provisions for data centers, and none have been formally proposed in unincorporated Cobb.

Under the draft ordinance, the Marietta Daily Journal reported, data centers would need a special land use permit approved by the board. Lot sizes would range from 5 to 30 acres, and facilities would be required to use power generated off-site. Buildings could not exceed 50 feet in height and would need a 300-foot setback from residential properties, churches, schools and daycares. Noise limits would cap at 65 decibels during the day and 55 at night. Outdoor lighting must be fully shielded, and the county attorney would have to approve a decommissioning bond before a facility could open.

Gambrill told the Marietta Daily Journal on Sept. 13 she wanted stronger residential protections, calling the 50-foot height limit near homes "part of the community pushback against data centers." Birrell said in the same report that the rules are "a start" but noted there are "still a lot of unknowns."

The work session can be watched on the county's website, on YouTube or on Cobb TV 23 on Comcast Cable.