Design+Construction News for Hurricane Prone Regions

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Single or Double Silicon Bead? The Answer May Surprise You.

by Crawford-Tracey Corporation (

Damage from hurricanes like Irma and Michael, made it abundantly clear that the standard industry tests for glazing systems are not always equal to the force and patterns of these storms. Variables like storm duration, wind and water pressure, glazing system design, fabrication and installation determine how fenestration performs both during and after an event. The result: Many windows and glazing systems leaked immediately, and then after those storms. causing a host of other problems.

So, what can be done? The answer lies in a well-designed glazing system that considers not only the installation of the system, but the adjoining wall cladding systems, roofs, and waterproofing elements, to name a few.

Structural sealants play an outsized role in determining the success of a system. So, let us deconstruct a popular myth. Many assume that a double bead of silicone is better than a single, in order to mitigate failures. According to Crawford-Tracey, a single bead under proper design may be more beneficial.

Why? The problem with double bead approach is that it can be a gateway to bigger problems. The development of a leak and the failure of the exterior sealant bead can result in delayed or masked indication of the failure. During this time, the water is diverted into the concealed cavities within the surrounding materials and continues to sit. Over time, the wet conditions may develop mold and sick building issues. A double bead masks the problem; a single bead allows you to quickly identify the problem and resolve it before more damage is done.

All of Crawford-Tracey systems are four-sided structurally glazed, face-sealed barrier wall systems; therefore, by the very nature of its assembly, only a single bead is required/necessary for the weather-seal. In the past thirty years, they’ve yet to see water infiltration problems, even in the oldest projects. They’ve been challenged, but have always come out on top!