Damp meter for walls (inexpensive) - recommendations?

[Mike D]

I'd like to buy a damp meter for assessing the damp situation in my house. There is some rising damp, which has been well-disguised by damp seal and wallpaper and etc. I mainly want to locate the worst areas so I can remove bricks in the wall and clear the cavities at those locations. (I'm convinced that the rising damp ocurs in places where the cavity contains debris which has piled up to above DPC level). Why do I care, if the problem has been well-covered up? Because I want to sell the place soon, and hope to minimise what will be found by a prospective buyer's surveyor.

I'm hoping that something costing less than £10 will do the job. Can anyone recommend one, or offer tips on choosing one?

Thank you,

Mike D

[Andrew Gabriel]

I don't think there is any such thing. Damp meters I've seen are all intended for timber.

However, if you want to use one on a wall, buy a cheap test meter with pointed probes which can measure 10Mohms, and they can be found for a lot less than £10.

[Graham.]

Multi-meter and two nails in a block of wood (?)

[EricP]

Buy a cheap multimeter with good resistance ranges and jab the probes into the walls. That will tell you much more than a toy "damp meter".

You will learn much more by sight and touch.

[Harry Bloomfield]

Mike D has brought this to us :

As others have suggested - a cheap and cheerful digital meter with a 10 or 20 Mohm range plus a couple of (very) sharp probes fixed into something to keep them a set distance apart and make them easier to use.

Then learn to use it- Even the moisture from your skin when touching the probes is enough to cause a reading, so take time to get used to what to expect. The lower the resistance, the more conductivity, the more moisture - but it could be simple surface condensation, so test when there should be no condensation about.

[The Medway Handyman]

So, what reading is 'normal' & what reading is 'damp'?

[Harry Bloomfield]

The Medway Handyman presented the following explanation :

That will vary from meter to meter, depending upon the voltage it uses at the probes. The higher the voltage, the more the damp plaster breaks down to conduction and the lower the reading displayed. Perfectly dry may produce an infinity reading.

The best bet is try it on some known to be dry plaster, then work from there.

[Andrew Gabriel]

A reading of >20Mohms is dry. (Dry isn't necessarily normal.) Reading also depends how far apart the probes are. IME, you don't need to worry unless you get something less than 1Mohm, but usually you'll get >20Mohms if dry.

[Mike D]

Great idea. I have one of those already. Thanks to all who suggested it. Actually, I may have to buy one.... one of the leads has pulled out of one of the probes on mine, and it doesn't look repairable.

Mike D

[meow2222]

maybe try plasterboard nails of the bright metal type.

Just dont kid yourself that these meters read damp accurately or diagnose damp problems.

NT