Capacitance/impedance testing is a non-destructive testing technique used to quickly and accurately identify water entry pathways and areas of entrapped water within a roof construction.  This technique is based on the ability of a material to store electrical energy.

It involves placing a moisture meter on the surface of the roof to send a safe electric current into the roof without penetrating the roof membrane. If the material is wet, the dielectric properties of the material would produce a higher meter reading than it would if the material were dry.

The Tramex Dec Scanner is a mobile device that is used for detecting relative moisture content of large roof areas. The Dec Scanner is designed for testing built up roofing and non-conductive single ply membrane. It provides instantaneous, clear indications of roof conditions and is able to detect as little as 2% excess moisture in these large-scale roofing systems.