Remember they read conductivity not damp not on mordern vans but older ones had what appeared to be silver paper lining on the back of the panels so you would automatically obtain a high reading
Well folks I've been having a read round about what 'damp meters' are and how they work. It seems that all a meter measures is conductivity. Yep that's it, nothing magic at all. I was beginning to wonder when I heard about the cost of some units being in the region of £130. What's that about, are they solid gold plated? They must be taking the p**s
I'm all for accuracy and consistency but for heavens sake a 1% variation in reading is unlikely to be here or there when the most significant element is first the material that is being tested which can offer a large range before you even add the complexity of water ingress.
It seem that most meters have a calibration for wood that is expressed as a percentage. They also have another ranged scale for use on brick which is necessarily less exactly portrayed.
So where does this leave the layman who really does not know the expected ranges for the range of materials used across the caravan spectrum and their variance with unwanted moisture contamination? Well I think all we can do is check like materials at similar penetration depths across the whole caravan. It is unlikely that the whole van is sodden (there would be other evidence) so the lowest reading would signify relatively dry parts but areas of a much higher readings are likely to be damp. What we are looking for are uniformly low readings, simple.
What do the experts think?
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"The trouble with the world is that the stupid are cocksure and the intelligent are full of doubt." - Bertrand Russell
The more expensive ones have sonic measuring tools as well as prongs which measure wood moisture equivilant basically a high reading in wood over say 14% could cause it to rot but in concrete would'nt be a problem I still swear by one of the best methods your nose if you have a damp caravan you can normally smell it as soon as you walk in it it's like a wet flannel left in the bathroom, an old trick used in the industry I used to be in but no good for caravans tape a small square of plastic on the surface make sure it's sealed leave it then look for condensation forming in it , if it does there's damp present. like i say no good for the caravan as we'd have no paper left on the wall
Witness the high number of people that come on here who have bought a caravan that "didn't smell damp" but has rotten framework and wallboard.
You can't usually smell it because it is trapped between two waterproof membranes - the aluminium skin on the outside and the waterproof vinyl wallboard covering on the inside. Unless there is a hole in the wallboard it won't smell. Thats why you need a damp meter.
We have a cheap damp meter and an expensive one. The expensive one is consistent, reliable and robust. The cheap one isn't.
Quote: Originally posted by hackaberry on 18/9/2013
I still swear by one of the best methods your nose if you have a damp caravan you can normally smell it as soon as you walk in it it's like a wet flannel left in the bathroom,
Maybe older vans, but that's not the case with a newer van, no smell no damp patch no bulges or dull sound when tapped.
Wallboards being replaced and it was found with a cheap 30 quid meter of flea bay !