What is the 25% rule in roofing?

In South Carolina, the 25% rule says repairing or replacing more than 25% of your roof in a 12-month window triggers a full code upgrade. Horry, Georgetown, and Brunswick County inspectors enforce it through the 2021 SC Building Code. After Helene or Ian, that math can push an older Myrtle Beach roof straight to a full rebuild once squares get counted. The forced rebuild covers new underlayment, drip edge, and code-compliant ridge ventilation. Ask your adjuster about code-upgrade coverage in your policy. It usually pays for the compliance work the 25% rule triggers, separate from storm damage.