Electronic Integrity Testing of Roof Membranes:

Principle of Operation

The D.C. Holiday Detector works by detecting the current flow in a circuit. The circuit is from the high voltage output of the Holiday Detector to the handle and to the material under test. The material is applied to a conductive substrate either steel or concrete (concrete is conductive due to the water contained in it) which is connected back to the Holiday Detector by its earth lead. If there are no faults in the membrane then no current will flow. When the electrode passes over a fault the high voltage jumps the gap between the substrate and the electrode and a current flows, the Holiday Detector detects this and activates its alarm. The membrane stops the flow of current and therefore must be non-conductive.

Method for carrying out the test

• The roof covering must be dry to allow the test to be carried out
• The roof area under test is given a visual inspection for and visible damage, all damage is marked on the roof with marker paint.
• The trained operative will then conduct the test of the roof and any impact damage or open laps are marked with marker paint so as to allow the roofing contractor to be able to make the necessary repairs.
• A written report is issued on completion of the survey.