LR Services will carry out a survey to provide you with an accurate picture of the condition of a flat roof area.

What is an electronic roof membrane survey?

It is a survey carried out by LR Services using the differential field analysis system. The component parts being:-

(a) The pulse generator
(b) The wire ring
(c) The meter
(d) Water
(e) The roof covering

The pulse generator gives 40volt negative at a 2 second delay (no risk of electrocution!). The necessity for the delay is to avoid electylic action.

This negative charge is transferred to the wire ring and the area sprayed with water. The water allows a fairly constant resistance between the roof covering and the building below (which is positive earth).
If a defect (breach in the membrane) is found the voltage gradient will be corrupted at this point, giving a zero reading on the meter. When a leak is found it is marked before being isolated from the test area allowing the scanning to continue.

In this way it is possible for an experienced operator to track ingress points through the membrane.

All leak points are marked on the roof area and recorded on a roof-plan and incorporated into a full report.

The materials that can be tested with this method are those that will form an insulating plate or membrane between the two polarities.

All single layer systems, poly-vinyl chloride (pvc) pvc/ethylene vinyl actate-terploymer (vet), chloinated polythylene (cpe), felt membranes and mastic asphalts can be successfully tested. However it should be noted that no system is able to test the integrity of metal component layers such as lead, copper or zinc. Also included in this category are certain ethylene propylenediene monomer (EPDMs).

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