Moisture meters - to detect dampness?

[Anonymous]

In my 1-bedroomed cottage, built c.1697, Rising Damp has been detected by a local surveyor using a hand-held 'moisture' meter. My estate agent instigated a survey from a local d.p. 'specialist' contractor, who used a similar device to gain readings "off the scale" & gave an estimate for remedial work in excess of £1,200. During this time, I was abroad for 6wks & neither survey was undertaken under 'normal living conditions', so I instructed my daughter to use a dehumidifier which I was sure would correct any high readings. For some peace of mind when home, I had a local builder check roof timbers & for dampness (he used a 'moisture meter' too!) His findings were in different areas to those of the 1st contractor - he believed that some were probably due to condensation, given the age & history of the building - estimate for remedial work, £352.

I'm perplexed & challenge their findings because there isn't evidence of any dampness anywhere in the property - visual or otherwise. I've visited your website, 'ask-Jeff.co.uk', Royal Insititute of Chartered Surveyors website (RICS article: Moisture Measurement in Masonry - Guidance for Surveyors.) & others & found similar articles questioning the accuracy & appropriateness of using such moisture meters.

From her surveyor's & 1st contractor's advice, my prospective purchaser is now reticent to take the risk of buying the property, & I can understand her concerns! Am I ever going to sell with this on-going problem? RICS advice is for me to consult an independent RICS surveyor, so I contacted one today but was told by a member of staff that they use 'moisture meters' & recommend work by 'Stoneoak', a local contractor - Oh, No! was my immediate reaction - said I'd call back, if necessary.

It's my belief we're being mis-led by all parties concerned - I'm reluctant to have any 'remedial' work undertaken if it could prove detrimental. I wonder how many home-owners have paid for unnecessary & costly work to be done? Homebuying reforms could probably be helpful in my situation.
I'd welcome suggestions & comments, please!
With thanks,

Lynn Whittaker

 

[Anonymous]

I'm often involved with testing of timber components which under various BS/EN codes have to be at a certain moisture content at the time of the joint being made and a different one at the time of test. Reliance on moisture meters is not allowed the joint has to be conditioned in a kind of kiln to a specific humidity and temperature which goes to show how little faith the authorities and techies have for moisture meters even in timber, after the test we have to do an oven dry check to make sure that the moisture content was in fact in the correct range.
If you do have to rely on a meter make sure that only the long insulated probes are used and that the are inserted about 20mm into the timber any less than this will just allow any surface moisture (condensation, rain etc.) to dramatically affect the readings. Most meters are set for a specific timber species and the readings need to be corrected for different species, used correctly by an experience person they are fairly accurate for TIMBER
Other than as a very broad indication I can see no sense in using one on plaster as there are too many variables that will affect the readings and none of the meters I have seen come with correction charts for materials other than timber.

 

[Anonymous]

I would not be rely fully on the results of a moisture meter to determine remedial works.

Ive inspected 2 period properties today both had readings on various walls, but there was no decorative spoling, plaster damage or risk of decay. My recommendations were to leave well alone and continue to monitor, will probably upset the other companies who had recommended £1,500 and £2,000 worth of work, but what the hell!

The trouble with the humble damp meter (as has been said) they are not designed for use on masonry, BUT can be used as an aid to investigation along as ised correctly and with you eyes and experience.

They are however non destructive.

My old friend Graham Coleman has a good web site with information on M/M its worth a look.

http://www.buildingpreservation.com

There are other methods of moisture measurement, speedy carbide and lab analysis, but they do obviously involve destructive drilling to obtain samples.

Regards

PC