# Damp Meter - What is an acceptable reading?



## Addie (Aug 5, 2008)

I've done a search and found a few comments that anything overy 20% on a digital damp meter "requires further investigation".

Would anyone else agree with this? I've bought a Damp Meter (arrived next day from eBay under a tenner here) and understand that at that price it is nothing more than a guide but would like to know what is considered an accpetable rule of thumb reading.

Cheers


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## DTPCHEMICALS (Jul 24, 2006)

Our son used to be a bench joiner and they liked to work with wood at around 20% or less.
This site will give you the information you require.
Dave p

http://www.globalwood.org/tech/tech_moisture.htm


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## Techno100 (May 8, 2010)

Buy a piece of dry ply and try it on that 
Dry
With condensation
Wet
Evaluate the readings


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## bigcats30 (Aug 13, 2012)

Just remember if its raining or just been raining when you did it then it could make the reading incorrect because of the moisture in the air.


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## happygolucky (Jul 18, 2006)

On my last water ingress report says 0-15% no moisture, 15-20% investigate, over 20% a problem. If the moisture reading inside the van goes up when it is raining, suggests a leak!!.

My personal view is if you spent £xxxxx on a motorhome, £50 once a year for a professional check is worth the money.

Brian


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## Antonia (Apr 27, 2008)

Hi

I got a meter from Maplin a few years ago.
First thing I did was create a map on the vans insides identifying 30 test points. Every few months i checked the readings at those points and kept a record. It is easy to see then if there is a problem, especially in winter when it rains a lot....well...all the time in the UK of course. Either way areas over about 20% MAY be a concern, but may change. Changes such as major increases indicate problems, obviously. A moisture map can be created which will also help indicate possible water ingress areas.

Antonia


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## WildThingsKev (Dec 29, 2009)

I understand damp meters but what I don't understand is this. Most motorhomes have an inner skin of some sort of impermeable sheet - so how do you get a measurement of damp in the structural timber behind?
If water is coming right through then it should be pretty obvious anyway and if you take the measurements in the wrong conditions there is always the risk of condensation giving false positives.
I've read so many times that a habitation damp test was clear then soon after a major problem was found.


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## Techno100 (May 8, 2010)

It's normally the outer skin that is impermeable 
The inner skin is usually 4mm ply and in between foam or polystyrene 
Penetration occurs anywhere where the outer skin has a joint or a hole cut in it for windows doors rooflights etc.
My auto cruise recently suffered leakage through the offside window and on removal/ refitting it was obvious that the constructor did not follow the fitting instructions of the window manufacturer.
So if a big player in the past like auto cruise can't do it right who can you trust :roll:


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## WildThingsKev (Dec 29, 2009)

Mmmm.. maybe I'm not that familiar with different manufacturers constructions but our Rapido has a "formica" type covering on the inside which I'm sure would be a barrier to damp.


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## Techno100 (May 8, 2010)

It's probably like a wallboard? Plywood with a posh finish as opposed to a vinyl paper covering.
Still the only way though is where holes have been cut in the outer skin and where the sealing system used was either never done correctly or failed though degradation.


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## kaacee (Nov 29, 2008)

happygolucky said:


> On my last water ingress report says 0-15% no moisture, 15-20% investigate, over 20% a problem. If the moisture reading inside the van goes up when it is raining, suggests a leak!!.
> 
> My personal view is if you spent £xxxxx on a motorhome, £50 once a year for a professional check is worth the money.
> 
> Brian


I agree Brian, but water ingress can occur a few weeks after it has been checked by the professional's as a/o/k. and then you may well be experiencing ingress for 10/11 months before your next scheduled check.

Therefore, I would suggest you purchase a damp meter £18 from Amazon and carry out your own checks on a more frequent basis just to ensure any ingress is identified early.

Keith


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