This paper evaluates the use of closed-cell Spray-Applied Polyurethane Foam (ccSPF) as a structural retrofit of existing wood-framed roofs. ccSPF is used as a thermal insulator in the building envelope and it forms a tenacious bond to most construction materials. As a result ccSPF is used to strengthen the wind resistance of wood roof structures. ccSPF is currently being installed in houses in Florida although the long-term performance of the material in presence of water is unknown. This study seeks to evaluate the effect of water leaks on the moisture buildup and wind uplift capacity of ccSPF-retrofitted wood roof panels.Nine full-scale roof attics were constructed and exposed to long-term environmental conditions and simulated rain in two phases, (five in Phase Ⅰ and four roofs in Phase Ⅱ). Numerous leak gaps were cut into the roofing systems simulating effects of long-term water leaks. It was found that moisture buildup occurs in roof sheathing and wood framing members, but it the increased wind uplift capacity of ccSPF-retrofitted roofs was not significantly affected. The high tensile strength of the water-saturated ccSPF to wood bond was confirmed in long-term tests using small-scale samples. While there was a reduction in tensile failure stresses after time due to exposure to moisture, the minimum values were more than xx psi, well above the wind uplift suctions producible by hurricane wind speeds. In the second phase, techniques to mitigate the moisture buildup were investigated. Preliminary results indicate that incorporating underside air vents within a ccSPF-retrofit may reduce the drying time of the roof sheathing. Further, installing a self-adhered waterproofing membrane underlayment on the roof deck substantially reduced the absorption of moisture into the wood roof system. A discussion of future testing is provided.
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