Do damp meters work?

Do damp meters work?

Articles about Damp

You might have heard that damp meters should not be used on surveys for issues of dampness, why is this? Here's the thing, electronic moisture meters do not detect moisture, they measure conductivity and interpret that as moisture, this because water conducts electricity. An implication of this is that other conductive materials can trigger these meters and the general conductivity of a base material can also influence a reading, i.e. concrete, plaster, metal (angle beads for example), and salts can all trigger a meter. Surely this makes them useless??? No.

Meters are actually calibrated to provide a relatively accurate reading within a typical softwood timber, and you can even use tables to differentiate for timber species, if you know what species the timber is.

They are accurate in timber because the base material is always relatively comparable, i.e. one softwood timber skirting board in a property is comparable to another in a different property.

Therefore, we can assess damp in timber beams/joists/skirting boards to a good degree of accuracy using a conductance moisture meter.

What about using them on walls etc?

Meters tend to have two pins for inserting into timber, and a plate which emits a radio frequency which is similarly influenced by moisture/conductive materials.

The plate can be used to assess walls without causing any damage to them, but you (I’m looking at all you property people that take damp meters on viewings without understanding how to use them)/the Surveyor, have to understand the limitations of these.

If you just put them on a wall in one location, the reading that is provided will not mean anything, however if these are scanned across the wall, for example from low level to high level and there are different readings across that area (of the same material such as wall plaster), then why is that? Does it correlate with anything else, leaking rainwater goods externally for example?

This is the crux of it, more information is always better – having information is never a bad thing, but in some cases you have to have the requisite knowledge to interpret this, and this is where it can fall down.

There are other forms of testing but that’s for another day/post.

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