damp detectors

[Arthur2]

S'me again. moisture/damp detectors for timber. There is a Draper damp detector on screwfix at 12.99. Is it accurate enough?

Arthur

[dg]

No such thing as a damp detector.

Most building materials have a moisture content, and others will have surface moisture. The meter will determine the presence of moisture, but its significance will need proper interpretation.

I know of many instances where supposedly professional surveyors place a meter against a wall, let it light up and proclaim to the homeowner/ tenant "Look, you have damp".

In addition, most if not all meters are calibrated for timber, and give inaccurate readings in any other material.

That particular meter, and other DIY ones are of very little use.

dg

[Arthur2]

So what do they use to detect moisture content of timbers after a kiln drying process? Timber sellers are always quoting 8 - 12% How is that measured?

Arthur

[dg]

With more sophisticated/accurate meters than a draper one ;-)

IIRC, kiln drying of timber is done by passing it through air of known humidity, which in turn equates to known moisture content depending on species. Timber will then settle to a moisture content related to surrounding air humidity

dg

[robgraham]

OK, I'll give the opposite opinion. I bought an inexpensive digital one off Ebay - they effectively all use the same principle - current flow between two probes which is dependent on something and I am satisfied that it is moisture in the wood !!

I'd got a lot of beech wood which I split into logs before the winter set in and stored under cover. These logs all showed no more than 20% right through in November - ie I split some and checked in the middle of the log and the moisture level was consistent. Some other beech was split later and was subject to more rain and consistently were 25%

• reading. I could have done a more scientific test like oven drying a log and measuring the weight loss, etc. but what I was seeing was evidence enough for me.

I made a query about Cheap Moisture Meters about 2 months ago and got slated for even thinking about them and am quite satisfied that what I got for a tenner gave me reassurance that the logs for my stove were dry enough.

Rob

[mail]

some measure resistance. some capacitance some use microwaves the only way to measure damp itself is the oven dry method for timber all other claims are based on correlation with another property which is that actually measured Chris

[mail]

It measures electrical resistance - not water - and that is not always proportional to the moisture content Chris