Cheap moisture meter for plasterboard

[mc2fool]

Had a surveyor round at my place yesterday and, to my surprise (as there's nothing at all visible), he detected damp behind a small section of plasterboard (that's up against a stud). Thinking I might get myself a moisture meter to monitor that I asked him which make & model he had and, well, it's a very expensive one.

There seem to be masses of them available around the £20-30 mark but it's not clear which would be suitable for my usage -- and it doesn't help that the listing for the top product at 10 Best moisture meters for plasterboard says "You are unrecommened to make test on pure drywall..."!

So, anyone got any recommendations for a moisture meter that'll work well for my usage?

[bungeejumper]

We run a few listed properties, so we have a lot of dealings with damp. We get on pretty well with our Stanley (£24), but it's important to recognise that they're never going to be perfect - they'll all help you to map the shape of the damp in the wall, but if you're looking for absolute numbers it's the wrong technology.

The thing is, those two prongs might be going through wallpaper or cardboard or damp sealant paint, or anything really before they give you their pseudo-precise readings. (People have been known to stick aluminium foil to a damp wall!) And how deep are you pushing, and a host of other questions?

You gotta take a holistic approach, because that's what a professional would do. I liked the warning about drywall. If it was drywall and it gave you a damp area in a well-heated room where nothing else was showing a problem, then you'd know that that was the superficial symptom. But the ultimate problem might still be a bad (or non-existent) damp course, or a damp exterior wall where the mortar had failed, or bad insulation in a cavity wall, a water leak, or a failed gutter coming down from two storeys up, or (insert bizarre alternative of your choice).

It might even be condensation, dammit! Any damp meter will help you to map the location of the problem, at least in relative terms. Some cheapo humidity meters will also give you useful info. From then on - well, that's what you pay professionals for....

BJ

[mc2fool]

Well, I suspect from where it is, close to the top of a dormer, that there might be a slight leak nearby that's finding its way to between the stud and the vapour barrier behind the plasterboard. Short of taking apart the roof from the outside it's inaccessible to check so really what I'm after is a meter just to monitor in the first place, to see if it does improve/get worse with weather, and then if I get roofers in to look at and try to fix it (it's a combination of steep tiles, lead gully and felt flat roof around there) to then monitor to determine if they did.

Got a link for the Stanley you use? Although the surveyor found it using the pinless detector on his (which makes me also suspect it's behind the plasterboard rather than in it).

Oh, the listing for the 2nd of the 10 Best moisture meters for plasterboard says "NOT suitable for measuring plasterboards, metal and cloth"!

Although it does say "Detects up to 3/4-Inch/19MM Below Surface", so does that mean it'll measure moisture behind plasterboard but just not in plasterboard?!?

Confusion, will be my epitaph ....

[bungeejumper]

Got a link for the Stanley you use? Although the surveyor found it using the pinless detector on his (which makes me also suspect it's behind the plasterboard rather than in it).

https://www.amazon.co.uk/Stanley-0-77-0 ... B003ASOBG8 . If you want pinless, "inductive" detectors can be had from around £25 (https://www.amazon.co.uk/Non-invasive-I ... 00MMW2H4G/)

Although it does say "Detects up to 3/4-Inch/19MM Below Surface", so does that mean it'll measure moisture behind plasterboard but just not in plasterboard?!?

LOL, no idea. Worst case scenario, if it's in the space beyond, you might need to make a small hole in the plasterboard and poke through in the most likely place with one of those long reach endoscope cameras (£20-ish, with lighting). You can often smell damp, BTW. But first, start by aiming to define the damp area as closely as you can. Even a really basic meter ought to get you that far. Best of luck.

BJ

[mc2fool]

Got a link for the Stanley you use? Although the surveyor found it using the pinless detector on his (which makes me also suspect it's behind the plasterboard rather than in it).

https://www.amazon.co.uk/Stanley-0-77-0 ... B003ASOBG8 . If you want pinless, "inductive" detectors can be had from around £25 (https://www.amazon.co.uk/Non-invasive-I ... 00MMW2H4G/)

Although it does say "Detects up to 3/4-Inch/19MM Below Surface", so does that mean it'll measure moisture behind plasterboard but just not in plasterboard?!?

LOL, no idea. Worst case scenario, if it's in the space beyond, you might need to make a small hole in the plasterboard and poke through in the most likely place with one of those long reach endoscope cameras (£20-ish, with lighting). You can often smell damp, BTW. But first, start by aiming to define the damp area as closely as you can. Even a really basic meter ought to get you that far. Best of luck.

BJ

Thanks for the links.

I know exactly where the area of supposed higher moisture is, I watched the surveyor moving his detector over it and he did it several times and from every possible angle. There are no human detectable signs at all, no smell, no stain, no damp feel, nothing. That's why it was a surprise!

[Dicky99]

https://www.amazon.co.uk/Stanley-0-77-0 ... B003ASOBG8 . If you want pinless, "inductive" detectors can be had from around £25 (https://www.amazon.co.uk/Non-invasive-I ... 00MMW2H4G/)

LOL, no idea. Worst case scenario, if it's in the space beyond, you might need to make a small hole in the plasterboard and poke through in the most likely place with one of those long reach endoscope cameras (£20-ish, with lighting). You can often smell damp, BTW. But first, start by aiming to define the damp area as closely as you can. Even a really basic meter ought to get you that far. Best of luck.

BJ

Thanks for the links.

I know exactly where the area of supposed higher moisture is, I watched the surveyor moving his detector over it and he did it several times and from every possible angle. There are no human detectable signs at all, no smell, no stain, no damp feel, nothing. That's why it was a surprise!

If there is rainwater ingress from around your dormer it will let you know about it as sure as the sun rises in the east. We've just had one of the wettest winters on record so with no smell, no stain, no damp feel I'm not sure what the problem is.

As for damp meters, the two prong types measure conductivity between the prongs and so as long as it does that simple function it doesn't matter whether it costs £10 or £100. Problem is that though a low reading confirms that a substrate is dry a high reading only tells you it might be damp. That's because other things than moisture are conductive, such as metals and some salts.

I wonder whether, if you're Surveyor is certain that there is damp behind the plasterboard, he discussed the possibility that it could be interstitial condensation i.e. condensate arising in, for example, Rockwool behind the plasterboard. If not you may want to ask him about that possibilty.

Generally speaking with rainwater ingress there is only a relatively short period of the structure secretly absorbing the water ingress before it starts saturating, staining, dripping etc.

[mc2fool]

If there is rainwater ingress from around your dormer it will let you know about it as sure as the sun rises in the east. We've just had one of the wettest winters on record so with no smell, no stain, no damp feel I'm not sure what the problem is.

Well, unless the ingress is really tiny and it's taken a soaking wet February to make this particular (and peculiar) limited area register.

I wonder whether, if you're Surveyor is certain that there is damp behind the plasterboard, he discussed the possibility that it could be interstitial condensation i.e. condensate arising in, for example, Rockwool behind the plasterboard. If not you may want to ask him about that possibilty.

He wasn't my surveyor, he's the surveyor of the woman that's going to buy my flat, and while he was chatty enough about the obvious as he went round ("ah, looks like there's some damp here", as the meter beeped and flashed orange...), when I asked him at the end if he could give me a heads up as to what was going to report I only got a good natured, sorry but you're not my client. So I await for the buyer to get the report, and to then (hopefully) forward it to me....