Whether a re-roof needs an engineer depends on the building and the jurisdiction, but in South Florida, many do. The Florida Building Code's existing-building provisions, roof-to-wall connection requirements, and the roofing product's own approval frequently call for signed and sealed engineering.
This guide explains the common triggers. It is general information, not a determination for your building. We confirm what your specific project requires before starting.
Roof-to-wall connections and re-nailing
On many older homes, a re-roof triggers a requirement to verify and, where needed, strengthen the connection between the roof and the walls, and to re-nail the roof deck to current standards. Demonstrating that these resist uplift generally requires an engineered form or sealed detail.
Attachment and uplift
Roof-zone uplift pressures depend on the roof's shape, slope, and your wind zone, computed per ASCE 7-22. The fastening and attachment must be shown to resist those pressures and match the roofing product's approval, which is where a sealed uplift table and attachment schedule come in.
Secondary water barrier
In wind-borne-debris regions and the HVHZ, the Florida Building Code (Existing Building, Section 706.7.2) requires a secondary water barrier, typically a self-adhering modified-bitumen underlayment bonded over the whole deck, so the structure keeps water out even if the primary covering is torn off in a storm. The applicable requirement is noted on the sealed set.
The 25 percent rule and the roof-to-wall retrofit
Two Existing Building Code provisions drive most of the engineering. Under the '25 percent rule' (Section 706.1.1 in recent editions), if more than a quarter of a roof section is replaced in any 12-month period, that section generally has to be brought up to the current code, not just patched. And when the covering comes off a wood deck, the deck is re-nailed to current attachment standards and the roof-to-wall connections are evaluated. Florida law also limits how much mandatory roof-to-wall retrofit can be required relative to the cost of the re-roof (see F.S. 553.844 and its implementing provisions). The exact threshold and how it is applied depend on the project and the version of the statute in force, which we confirm before scoping the work.
Which of these apply, the governing code edition, and the exact fastening, connection, and cost-cap details depend on your roof and jurisdiction. We confirm the triggers for your building and show the load path on a sealed set.
Questions
What is the 25 percent rule for roofs in Florida?
Under the Florida Building Code, Existing Building (Section 706.1.1), if more than 25 percent of a roof section is repaired or replaced within 12 months, the whole section generally must be brought up to the current code rather than simply repaired in kind. Whether it applies to your project depends on the scope, which we confirm.
Does every re-roof in Florida need an engineer?
No. Some re-roofs are permitted without sealed engineering, while many, especially older homes and those in the HVHZ, require engineered connection, re-nailing, or attachment work. The requirement depends on the building and jurisdiction.
How do I know if mine does?
The building department and the roofing product's approval determine it. Send us the address and scope and we'll confirm whether your re-roof needs a sealed package before you commit.