Patent ID: 8319508

Claim:
A method of locating a defect in a water impermeable membrane of a roof, where the roof comprises a generally horizontal roof support deck with the water impermeable membrane applied onto an upper surface of the support deck, the method comprising: locating a conductive detector on an upper surface of the roof membrane; defining a shielding zone on the upper surface of the membrane by providing at least one shielding conductor on the upper surface and by generating an electrical potential difference between said at least one shielding conductor and the roof deck such that currents generated outside the zone are drawn to said at least one shielding conductor; generating an electrical potential difference between the conductive detector and the roof deck such that, in the presence of a defect located within the zone, current flows between the roof deck and the conductive detector through moisture at the defect; sensing the current between the roof deck and the conductive detector so as to detect any defect located within the zone; and arranging the electrical potential difference between said at least one shielding conductor and the roof deck so as to be greater than the electrical potential difference between the conductive detector and the roof deck.