Moisture Detection in Roofing
Plastic Sheet Method
Lay down a 3′ x 3′ black trash bag or a heavy rubber mat over the suspect area and tape all sides. Wait overnight and peel back one corner and check for condensation underneath the sheet.
Moisture in roofing can be detected with an infrared camera. They are performed after sunset, when the roof starts dissipating the heat absorbed during the day. Areas with moisture will hold more heat energy that dry areas. As a result, moist areas are clearly visible in an infrared scan.
Non destructive moisture meters use low-frequency signals to detect changes in impedance caused by a variation in moisture content. The reading is instantaneous and can be used to quickly check the moisture content of a substrate before coatings are applied. A reading of less than 4% is ideal.