Do I need a permit for addition or structural alteration in Unincorporated Cobb County?

Yes. In Georgia, addition or structural alteration generally requires a permit, and Unincorporated Cobb County is no exception.

Additions and any change to load-bearing walls require a permit and reviewed plans in Georgia; removing or altering a bearing wall usually needs engineered details. Additions may trigger energy-code, zoning, and setback review, so confirm the full scope before starting. Cobb County's own permitting office is the Cobb County Development and Inspections, reachable on 770-528-1000 at https://www.cobbcounty.gov/community-development/building-development/permitting. Its online permit portal is https://cobbca.cobbcounty.gov/CitizenAccess/default.aspx. It issues permits for the unincorporated county. If your city does not run its own building department, and many smaller Georgia municipalities do not, this is the office that will handle the job. Cobb County sits inside the Metropolitan North Georgia Water Planning District, created by the Georgia General Assembly in 2001. Every local government in the District, cities included, has to adopt the District's model post-construction stormwater ordinance or an equivalent one at least as effective, so these rules follow you into any city in the county rather than stopping at the unincorporated line. An addition adds roof area, which counts as impervious surface, and a large one combined with new driveway or patio work can reach the local threshold. In practice the thresholds are aimed at larger development rather than ordinary homeowner work, so most single-family projects sit below them. Cobb County, for example, publishes its trigger as adding more than 5,000 square feet of impervious surface or disturbing more than an acre. Each local government sets its own figures, so check yours before assuming. Where it does apply, the current standard is to retain the first 1.0 inch of rainfall on the site to the maximum extent practicable, which usually means a detention or infiltration feature rather than just grading water to the street. Cobb County requires an Addition Permit for every attached structure that adds to the home's footprint, including decks, patios, porches, sunrooms, rooms, garages and carports. A homeowner acting as their own general contractor on an addition must hold a preconstruction consultation with the Chief Building Inspector before the permit is processed, can do so only on the home they live in, and cannot pull the permit if a contractor is doing the work. A zoning compliance inspection after the foundation and before framing checks the 35-foot height limit and setbacks, and the application certifies the project stays within the zoning district's maximum impervious surface (35 percent in R-20). The permit stays active only with a passing inspection at least every 60 days and expires at 180 days unless renewed for a fee.