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Differential Pressure Testing of Waterproofing Membranes

Electronic leak detection of waterproofing membranes has become increasingly popular in recent years and is a quicker and simpler process for detecting leaks in a roof than the flood testing.


It is not affective in all situations, however, so Thornton Consulting developed Differential Pressure Testing for when electronic leak detection is not possible.


Electronic leak detection relies on the conductive properties of the structural deck and insulating properties of the waterproofing for the test operate accurately. Where one of these parameters differs, the test will not be affective. For example, an electrically conductive membrane such as EPDM or non-conductive deck such as timber cannot be tested with the electronic leak detection method.


This is when Differential pressure testing is used to establish the integrity of the waterproofing. It is a non-destructive test whereby negative pressure is created in a vacuum chamber to locate breaches in membrane laps. Air is drawn through a surfactant, applied to the surface of the membrane, which will indicate the location of the breach or open lap.


This test can also be used for warm roof constructions where the insulation is non-conductive or does not have a conductive surface.  In such situations, if there is not a conductive path between the surface of the membrane and the deck, electronic leak detection methods may not be suitable. Again, differential pressure testing can be used to establish integrity of laps and is particularly useful on single ply membranes, such as pvc and tpo and felt systems.


Further development of this test procedure has allowed testing to entire roof areas with our bespoke equipment. With this, integrity testing can be undertaken to vulnerable areas of waterproofing, for example, where all breaches need to be located and repaired prior to installation of other equipment, such as plant or PV panels etc.


If you would further in formation of this or any of our other services, please contact or office on 01342 410508 or visit our website


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