<title>Use of an infrared scanner and a nuclear meter to find wet insulation in a ballasted roof</title>

Abstract

An IR scanner and a nuclear moisture meter were used to survey a ballasted roof suffering chronic leaks. Infrared surveys, conducted with the ballast in place, uncovered five small wet areas. The thermal anomalies were faint and may have been missed during a routine IR roof moisture survey. Nuclear readings were taken on a 1.5-m (5-ft) grid. HIgh nuclear readings were obtained at the one grid point that fell within one of the five wet areas detected during the IR survey. The other four wet areas were missed. However, the nuclear meter found an additional nine small wet areas that the IR scanner missed. All but one of these areas contained wet urethane insulation directly below the membrane. In three other areas of the roof, nuclear readings were higher than those over the rest of the roof. Core samples verified that the perlite insulation at the base of the roof was wet in these areas, two of which were small but one was 12 X 12 m (40 X 40 ft) when squared off. This `deep' moisture was not detected thermographically. On this roof IR and nuclear surveys both provided valuable information but each missed a portion of the problem. When used in combination, their strengths were complementary.