Over the years, investigators taking a close look at hurricane damage in Florida have learned that many buildings have a common vulnerability: weak connections between wall framing and roof framing at the gable ends. The result has been a typical pattern of damage: gable end walls get sucked outwards by the wind. Then the building is exposed to rain entry, damaging insulation, drywall and contents. Worse still, the loss of the gable end can be the first step in a series of collapses that ends in destruction of the whole house. Since 2007, Florida has required contractors to reinforce that key connection during some remodeling or re-roofing work. The retrofit solution involves braces nailed to gable-end framing and to ceiling joists and rafters or roof trusses. Coastal Connection explored Florida’s retrofit requirements in two articles in 2008: “ Gable-End Retrofits” (May 2008), and “ Strengthening Roof-to-Wall Connections” (November 2008), both authored by long-time contractor and building consultant Richard Reynolds.
Reynolds helped to craft the Florida requirements, and he explains that they’re based on careful engineering calculations. But nobody knows for sure how well these details will actually perform in the field over time, as they’re tested by actual storms. To get more insight into that question, Reynolds and engineer Tim Reinhold of the Institute for Business and Home Safety (IBHS), a research and education non-profit funded by the insurance industry, have been conducting laboratory tests of the system in IBHS’ multi-million-dollar wind research facility in South Carolina.
Reinhold and Reynolds conducted testing earlier this year on full-scale buildings framed conventionally, and equipped with retrofit reinforcement as specified in Florida’s building regulations, or as detailed in the Wood Frame Construction Manual (WFCM) published by the American Forest & Paper Association (AF&PA). They subjected the buildings to wind suction, and measured the temporary deflection in the assemblies, as well as any permanent deformation that resulted from the wind action.
They’re still evaluating the results. Observations, conclusions, and recommendations will be published some time in 2013. But one observation is already emerging: Not surprisingly, the results indicate that balloon-framed gable-end walls are more resilient than walls that are framed with a hinge joint at the first story ceiling.