Damp tester

[tapdave]

I have just purchased a damp tester . I have used it and have been shocked that my interior is reading wet everywhere .

However through a process of illimination it seems that all wet readings are very close to metal aluminium strips ..I was agast and most concerned but I now know it reads wet even when I put it on anything metal , even on a screw driver or screw head ,,,please can I ask if these testers are accurate.?…I bought it from Temu and was about £30… the reviews were excellent??mmmm’. Thank you all

 

[Googlebot]

In a word, yes.

They only work on wood generally though I have found.

 

[Terry]

What readings are you getting?
Upto 15 is good 15 /25 needs investigated (damp) 25/30 is damp
30 and above is wet so don’t buy

 

[Kannon Fodda]

Damp meters were originally designed and calibrated for moisture content in wood. "dry wood" inside a heated building is still likely to have a moisture content of 7%-9%. Use on anything else can have variable results and you need to be able to understand what the meter may be telling you along with other clues from the environment.

Pin type meters work by trying to pass a small electric current through the material into which the pins have been pushed. If moisture is present the current moves with less resistance. But in materials like plaster, brick, concrete, natural salts and other chemicals can affect the conductivity and thus give false readings. Frequently "damp" in buildings can be the plaster having salts that have been drawn from brick into the plaster.

The modern, non invasive, meters try and work by radio frequency or capacitance of the material. Possibly OK where the material itself is uniform in thickness and density, but voids such as small gaps in brick or concrete will upset them. Of course, where they are being used in a motorhome and the materials are thus thin, anything immediately behind such as the metal skin of a panel van, wires, and such like can give false readings.

So damp meters are a useful diagnostic tool, but one then has to look further to understand what it may be telling you.