Chapter 9 applies as published
The Georgia DCA amendments to the 2018 IRC (revised January 1, 2020) amend Chapters 1, 2, 3, 5, 6, 8, 13, 16, 19 and 24 only. There are no R9xx amendments. That means the Chapter 9 (Roof Assemblies) rules on slope, underlayment, flashing, drip edge and reroofing apply in Georgia exactly as the IRC prints them.
Traps to reject outright:
- Georgia did not replace Chapter 9 with its own state roofing chapter.
- Georgia did not delete the reroofing section or hand reroofing to local ordinance.
- Georgia did not amend the drip edge or valley rules.
Assuming Georgia changed Chapter 9 is the common error.
The one deletion: R806.5 Item 5.2
Georgia's roofing-related deletion is outside Chapter 9. Page 12 of the DCA amendments reads: delete R806.5 Item 5.2 without substitution, effective January 1, 2020. R806.5 covers unvented attic and unvented enclosed rafter assemblies.
Keep the neighbours straight:
- R806.2, the minimum attic vent area rule, was not deleted. Only Item 5.2 of R806.5 was.
- R905.2.8.5 (drip edge) and R908.3.1.1 (re-cover limits) are Chapter 9 provisions, and Georgia did not touch Chapter 9.
Appendix U is optional
Georgia's local-ordinance roofing item is Appendix U (Disaster Resilient Construction). It is an optional Georgia appendix; the DCA text says local jurisdictions adopt it by ordinance. So the AU408 two-layer secondary water barrier applies only where the local jurisdiction has adopted Appendix U.
Treating AU408 as a statewide mandate on every new one- and two-family dwelling is the common error. Two other wrong limits show up as distractors:
- AU408 has no 4:12-or-less slope condition. The 4:12 figure is the OSHA low-slope definition (29 CFR 1926.500), not an Appendix U limit.
- AU408 is not a re-cover rule. Re-cover limits live in IRC R908.3.1.1.
Quick recall
- Chapter 9: no Georgia amendments.
- R806.5 Item 5.2: deleted, no substitute, effective January 1, 2020.
- Appendix U / AU408: applies only where adopted by local ordinance.