Moisture meter

oldbilbo

oldbilbo

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Surveyors occasionally use a moisture meter with twin probes to investigate timbers and hull areas for 'relative' degress of entrapped damp. This would also seem relevant to DIY repainting, and I'm wondering if a cheaper device would be helpful to the likes of us, such as this at around £50 - no, £27 via PVR CLub.....


AK2020.png
 
Probably of use, yes. I recall some years ago a comparitive table was published in PBO for readings on the three main makes of meter used by surveyors - but even then there was a caveat that direct conversions may not be reliable. But if you're monitoring condition over a period or during work, then it should indicate the relative state of the substrate. I'd hope that it would yield useful data say in the Spring as a window frame dried out - when it plateaus you may as well paint it. This time of year in the UK it is probably a pointless exercise - it's damp, period!

Rob.

P.S. posted with paint stained hands - last coat on a window frame...
 
oldbilbo said:
Surveyors occasionally use a moisture meter with twin probes to investigate timbers and hull areas for 'relative' degress of entrapped damp. This would also seem relevant to DIY repainting, and I'm wondering if a cheaper device would be helpful to the likes of us, such as this at around £50 - no, £27 via PVR CLub.....


AK2020.png
Click to expand...

Mind you, nothing worse than the uneducated running around with a moisture meter and not being able to interpret the results. Had a bloke view our old boat with a moisture meter set on the deepest setting - proclaimed the hull was saturated and needed an osmosis treatment. Problem I had was that it had just completed a full professional treatment under surveyor supervision - and hadn't been in the water since. There was no convincing the guy! So buyer..........................and seller beware!!!
 
Moisture meter users beware.

There are in general use in the timber industry two types of moisture meter.
1 The simple device has two probes and often a slide hammer to drive the probes into the substrate. Useful cos it measures at a set depth.(The probes are insulated except for the very tips.)
2 the other is a capacitive probe and works by laying the unit on the surface.

There may be others that i am unaware of however:

These DEVICES DONT MEASURE MOISTURE CONTENT!!!!

What they measure is conductivity or capacitance.
This can be used to calculate an approximate moisture value if appropriate correction factors for wood species, Heartwood/ Sapwood content, absence or presence of treatment chemicals, timber density and state of the moon are all thrown in. (It helps to wet your finger and hold it in up in the wind as well.)
The point is it is not like measuring volts with a volt meter: Just cos a moisture meter says 14. 2% it is not necessarily so!

If you know what you are doing and know what you are measuring and have the appropriate table of corrections you can get good comparative values, but for one off uses on unknown timbers (or fibreglass) you may as well throw a dart at a dart board.
The only guaranteed reliable accurate method to assess moisture content is to take a sample and weigh it and then dry it at ~110 degrees C until consecutive hourly weight checks on lab scales show no change.
Difference between initial weight and final weight is the moisture originally in the sample.
This is how we derive correction tables for Moisture meters for different species and the effect on conductivity and capacitance of different timber preservatives.

Certainly as a result of my experience in the timber and timber preservatives industry, i treat any stated moisture content with total scepticism until i can verify the meter and the methodology!:rolleyes:
Good luck.
 
robmcg said:
Mind you, nothing worse than the uneducated running around with a moisture meter and not being able to interpret the results. Had a bloke view our old boat with a moisture meter set on the deepest setting - proclaimed the hull was saturated and needed an osmosis treatment. Problem I had was that it had just completed a full professional treatment under surveyor supervision - and hadn't been in the water since. There was no convincing the guy! So buyer..........................and seller beware!!!
Click to expand...
Yes, I thought the use was in identifying differing amounts around the hull, that MIGHT indicate something was abnormal in a specific area.
LIDL were supposed to have some for a tenner at the moment
 
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