What does the building code require for attic ventilation, and when does it apply to your house?
How the code reaches your project
- New construction: ventilation is designed in and checked during framing and insulation inspections.
- Roof replacement: many Georgia cities and counties require a permit, and inspectors focus mostly on the covering, underlayment and flashing. Whether anyone checks the vent math varies by jurisdiction.
- Additions: the new attic space must meet the current code, and it often ties into the old attic, which changes the totals.
- Finishing an attic or vaulting a ceiling: each enclosed rafter bay needs its own vent channel, or the assembly must be built as unvented under the code's separate rules.
Existing houses
Codes generally govern new work. A 1985 house built with gable vents only can usually stay that way until you do work that touches the attic. The moment you replace the roof, though, it is the logical and cheapest time to bring ventilation up to today's standard.
The other rulebook: your shingle warranty
Shingle manufacturers write ventilation requirements into their limited warranties, often referencing the same ratios. A roof installed over a poorly vented attic can face warranty questions later even if no inspector ever looked. That makes the warranty, not the permit, the practical reason most reroofs get a ventilation check.
Who to ask
Your local building department decides which edition and local amendments apply on your permit date, and the Georgia Department of Community Affairs publishes the state amendments. Read roofing permits in Georgia and roofing warranties explained for how the two rulebooks overlap.