Moisture Meter Testing
The electrical resistance and capacitance meter is easy to use and provides rapid results. This is a non-destructive technique, which is used principally on the surface of the building component, although deep probe techniques can be used. Simply pressing the probes or capacitance pad against the building material provides an immediate moisture content reading.
The meter is usually calibrated for timber components, giving very accurate results when used in timber. When used with other building materials, eg plaster, brickwork, etc, some calibration of the moisture scales supplied may be necessary and readings are not then referred to a moisture content percentage but high medium or low.
Care is needed in interpreting the results; the electrical resistance method generally provides an indication of surface moisture, although deep probes are available. This surface reading may not be representative of the overall moisture content of the component. In addition, naturally occurring mineral salts, timber preservatives and embedded metals can affect the electrical resistance of the material and subsequently the measured moisture content. Some preliminary investigation or laboratory tests may be required to quantify this level of interference.
The resistance meter method is particularly useful for looking at changes in moisture content. When looking at the drying-out of a building after wetting, the absolute moisture level may not be of particular importance as it may be exceptionally high. However, when the moisture content results are compared over time, it is the regular drop-in moisture content that is important. The electrical resistance meter is a particularly useful tool for keeping records and monitoring the rate at which moisture content is reducing or changing.
Capacitance meters can detect moisture 4 cms into the fabric thus are useful in differentiating between environmental moisture and rising damp.
Patterns of dampness can be mapped to create a profile commensurate with leaking downpipes, penetrating dampness, lateral damp caused by high ground and rising damp.
Once an area is pinpointed and further confirmation is required the carbide meter can then be used to determine moisture content.