Mike Silvers, CPRC, Owner, Silvers Systems Inc. and FRSA Technical Director
Under statute 553.844 Windstorm Loss Mitigation; Requirements for Roofs and Roof Opening Protection, Florida mandates that the Florida Building Commission develop and adopt certain mitigation techniques that, among others, include improvements to roof-to-wall connections. Through its rule making authority and procedures, the Commission has adopted criteria that mandate when evaluation and possible improvements of the roof-to-wall connections are required by the Code. The Florida Building Code-Existing Building, Chapter 7 Alterations Level 1 states:
706.8 When a roof covering on an existing structure with a sawn lumber, wood plank, or wood
structural panel roof deck is removed and replaced on a building that is located in the windborne
debris region as defined in the Florida Building Code, Building and that has an insured value of
$300,000 or more or, if the building is uninsured or for which documentation of insured value is not
presented, has a just valuation for the structure for purposes of ad valorem taxation of $300,000 or
more:
(a) Roof-to-wall connections shall be improved as required by Section 706.8.1.
(b) Mandated retrofits of the roof-to-wall connection shall not be required beyond a 15 percent
increase in the cost of reroofing.
Exception: Structures permitted subject to the Florida Building Code are not required to comply
with this section.
The reroofing of a structure located in the windborne debris region (WBDR) can trigger the need to address roof-to-wall connections, as well as the need for impact-resistant skylights, so understanding where these regions are and how they are defined is important to roofing contractors. Figure R301.2(4) below shows in blue the current locations of the WBDR.
The following is from Chapter 2 Definitions in the code (bold added for emphasis):
WINDBORNE DEBRIS REGION.
Areas within hurricane-prone regions located in accordance with one of the following:
1. Within 1 mile (1.61 km) of the coastal mean highwater line where an Exposure D condition exists upwind at the waterline and the ultimate wind speed, Vult, is 130 mph (58 m/s) or greater.
2. In areas where the ultimate design wind speed, Vult, is 140 mph (63.6 m/s) or greater; or Hawaii.
I emphasized the word "coastal" in the definition above for an important reason. In the original version of the 2023 Eighth Edition of the Florida Building Code (FBC), through the adoption of ASCE 7-22 and portions of the International Building Code, the word "coastal" was removed. This may seem like a minor change – it is anything but. The deletion of the word "coastal" meant that one mile from an Exposure D condition that is created over open water with at least 5,000 feet of fetch in the upwind direction – including large inland water bodies, such as lakes – would be considered a WBDR. It was only due to a seldom used code modification procedure known as an Annual Technical Amendment – passed after the implementation of the code – that the enforcement of this very troublesome change was averted. However, that fix may be only temporary. “Coastal” may once again be removed in the 2026 Ninth Edition FBC or with the adoption of a new ASCE 7 standard in the future. The areas impacted by the potential inclusion of the lakes is depicted in light blue on the maps in Figures 1, 2 and 3 on this page.
Section 2 (above) of the definition of a windborne debris region is simple and straightforward and states:
In areas where the ultimate design wind speed, Vult, is 140 mph (63.6 m/s) or greater; or Hawaii.
You verify the wind speed based on the code wind maps or by using the ASCE 7 Hazard Tool (ascehazardtool.org). If the wind speed is 140 mph or greater, you are in the WBDR. The other section of the current definition is where it gets complicated. In section 1 (page 14), it states:
Within 1 mile (1.61 km) of the coastal mean highwater line where an Exposure D condition exists
upwind at the waterline and the ultimate wind speed, Vult, is 130 mph (58 m/s) or greater.
As you can see, there are a lot of caveats in section 1. First, you need to confirm where the coastal mean highwater line is located. This line can be very difficult to locate or verify. Then you must establish if your job is within one mile of that obscure line. The narrow-dashed lines shown on page 12 in Figure R301.2(4) represent the locations along the coast between the 130 mph and 140 mph contour lines that are currently included in the WBDR. The location of inland WBDR in Figures 1, 2 and 3 would be even harder to establish if they were to be included in the code. Attempting to find the exact location of your job on these small maps is difficult at best.
Two code modification proposals have been submitted for the 2026 Ninth Edition FBC that would again strike "coastal," once again adding inland WBDR to the code. If successful, this change would cause significant confusion when trying to establish where a WBDR is located relative to a specific property. Even if these 2026 FBC modifications aren’t approved, this change could very well occur through the adoption of other code.
Alternate language to simplify this code requirement was recently brought to our attention. This proposal would change the WBDR definition to:
Designated areas where the ultimate design wind speed, Vult, is 130 mph (58 m/s) or greater.
This definition would add areas in Central Florida and the Panhandle to the WBDR (compare Figure 4 below to Figure R301.2(4) on page 12 ) but eliminate the confusing language – "within 1 mile from the mean highwater line" – that, as we have said, is hard to verify. The tradeoff is a well-established, simple and verifiable WBDR boundary that will make contractor compliance much more straightforward.
During a July meeting of FRSA’s Codes Subcommittee, this issue was discussed and a decision was made to support the effort to simplify the WBDR requirements moving forward.
Note: Several figures used in this article were taken from a report titled: Investigation of the Windborne Debris Regions in ASCE 7-22, prepared by the Engineering School of Sustainable Infrastructure and Environment (ESSIE), University of Florida (UF) presented to and accepted by the Florida Department of Business and Professional Regulation, Florida Building Commission.
FRM
Mike Silvers, CPRC is Owner of Silvers Systems Inc. and is consulting with FRSA as Director of Technical Services. Mike is an FRSA Past President, Life Member and Campanella Award recipient and brings over 50 years of industry knowledge and experience to FRSA’s team.
