Last edited 23 Mar 2021

Carbide meter

When identifying damp in buildings, architects, surveyors etc may use moisture meters to confirm or obtain a diagnosis. In skilled hands with regular site calibration, moisture meters can be a good starting point.

Carbide meters are one method of measuring moisture content. This technique (sometimes referred to as Speedy Carbide Test after the manufacturer’s name) works by testing a weighed sample of drilled mansory that has been taken from a sample area such as a mortar joint located above the damp proof course. This sample is then placed in a container. A measured amount of calcium carbide powder is placed in a separate portion of the container, and then the container is sealed. The container is shaken and the two substances mix together to trigger a reaction that produces acetylene gas if moisture is present.

The meter will indicate the results of the test. Readings will range from 0 to 5, with a higher number indicating a higher level of moisture.

Carbide meters are likely to give a more accurate measure of moisture content than some other techniques, although they require the removal of a sample - which could be considered by some as destructive. As a result, this method of testing may only be advisable after an electronic meter, or some other method has indicated the presence of moisture.

For more information see: Assessing moisture in porous building materials.

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