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Accurate Moisture Contents and Cut Outs

A more thorough investigation invariably involves taking accurate moisture content readings to build up a picture of moisture ingress and making cut outs to see what is really going on and collect information about how specific parts of the house were put together.

It is reasonably fair to place the various techniques within a hierarchy: non invasive tools such as surface meters and infrared cameras at the bottom, accurate moisture content readings (via a resistance meter) in the middle and cut outs at the top - the information obtained from a cut out is far harder to argue with than information collected from the middle and lower level techniques.

Sometimes you may hear it said that accurate readings of the moisture content provide some kind of certainty, for instance that a low reading (say, 12% - 15%) means the timber is undamaged.

Unfortunately, as the photos below illustrate, the truth can be less simple.

rotted timber

This timber is very obviously severely decayed - it quite literally came away in my hand, although there was not the slightest visual indication either externally or internally in this area - this advanced decay was completely hidden.

However, the real point if these photos is to show how timber very close to the decay appeared clean, hard and dry:

14%

The accurate meter is showing 14%, it is a heavy set of prongs which is driven in and the timber is strong enough to support their weight, despite its decayed state. 14% is generally considered a nice, safe, secure reading.

This illustrates why it can be unwise to rely just on accurate readings. And it is one of the reasons why I like The Probes - shavings are collected and the timber strength tested at the same time the accurate readings are taken so you get three very useful bits of information from each one. A probe inserted in the bottom plate in the corner of this room from inside would have at least found an area which required further investigation.