While trying to find a suitable method testing Gyvlon floors for moisture this is all I come across. I have searched various flooring websites with no further success. Anyone else come across a Hair Hygrometer ?

Adorini hair hygrometer: Amazon.co.uk: Kitchen & Home

Please correct me if I'm wrong Neale but, that looks like it is only designed to take the relative humidity from the air, most of the hygrometers that I've looked at have a probe that needs to be put in a drilled hole in the screed and left for 60 mins to give an accurate reading of the moisture content, and they aren't cheap.

There was a link to this site in your link, Timber & Building Moisture Meter with Heavy Duty Hammer Probe I think this is the sort of thing to be giving a more accurate reading.

This is the problem here....We dont know, but we need to know. I spoke to a flooring company today and they said to use a digital one. I have been told by others that these are not accurate.
If you dont ask these questions you never know.

As it would happen I'm doing a gypsum floor at the moment and I went out to do a moisture content check last week with a digital hygrometer and it was not much use as it seemed to be picking up the water in the UFH!!! The only place it gave an accurate reading (dry reading) was inside a stud wall where there was no pipework underneath, I didn't use a probe just the testing sensor on the rear of the unit. I think to get an accurate reading a probe in the screed is required.

We are currently doing some work on this to compare digital with hair. The main reason for this is because hair hygrometers are so difficult to get hold of. We find that digital ones are only accurate at rh readings between about 70 and 85. Also bear in mind that there is a fiv percent tolerance in the reading so a dry floor will show 75 plus or minus 5 percent I.e it is dry at 80. The primary issue here is due o the compatibility issues using cement and gypsum together. Gypsum on gypsum is much more robust making the absolute accuracy of moisture testing less important. The hygrometer you found Beale will work. You would place it on a ouple of matchsticks so it is just off the floor. Then over the area with a piece of polythene and tape it down to the screed. Clear polythene is best so you an read through it. Leave it in place for 48 hours and see what it says. The main issue with this type of device and the reason people are now going digital is that the calibration is quite sensitive. I actually use a teamed moisture meter as a survey tool. It seems to work relatively well. The protameter hygro hoods are also quite good. The carbide bomb is accurate when used correctly and is the european test of choice.

Bri . A digital hygrometer won't read the water in the pipes. I assume you mean an electronic probe meter?

Yeah Alan it was a protimeter device, it gave consistent readings of 240 (at risk) and in areas with no ufh reading sub 150. Couldn't think of a reason why? I didn't use the probe just the unit itself.

I thought it was a spoof hair growing device...

If it were MG I would be wearing one on my head right now.....

Bri - yes that would explain it as the protameter works on (I think) microwave technology it will pick up other sources of water.

to check rh readings in concrete use a hygrometer such as protimeter hygromaster get a couple of blank boxes, then use a damp meter to check best areas for putting them down it's the ONLY way apart from dropping the sensors into the ground and allow a minimum of 48 hours for data collection. The best ones cost around £600-700 Protimeter mms or Tramex CMeXpertII, this is the only way to check moisture content to British Standards reading in Rh%