Need to lay Solid Wd floor over 3 different sub floors HELP

[mattysupra]

To use that meter you need the plugs for it or box. The plugs are yellow and you drill lets say 3 holes into the concrete and put the special plug into the floor. You then leave for 24-72hrs before you can take a reading ( the plugs are sealed while in the concrete )
You can also use the box. This is the same as a hygrometer box without the hygrometer built into it. It has a air chamber which is bonded to the floor so that the amount of moister coming out the floor gets trapped so you can get your RH reading ( relative to humidity )
You really need one of these two items to get a correct reading. Your method with the plastic might work but might also give false readings due to condinsation, temperature change ect.
Also as this meter reads in RH then you need to be at about the 60% and below mark.
What is the humidity of the room?

 

[mattysupra]

http://www.protimeter-direct.co.uk/accessories.htm

You need humidity sleeves or humidity box. I would go for the sleeves as the box needs special tape ect to stick to the floor and also you can test 3 or 4 areas at the same time with the sleeves without having to wait days between.

 

[scottylowe]

Hi mattysupra,

Currently the RH meeting in the room (which is open plan with the whole of the ground floor) is 67%. The last meeting taken this morning under the Plastic was 81%.

If I use this 60% target I may never get to lay the floor.

The plastic method was described to me by the surveyor who sold me the protimeter as she used to do this to prove damp in court cases. do you really think it will be that inaccurate?

Thanks, Scott

 

[mattysupra]

The plastic method was described to me by the surveyor who sold me the protimeter as she used to do this to prove damp in court cases. do you really think it will be that inaccurate?

Thanks, Scott

First of all they are speaking rubbish. The ONLY test to british standard that will stand up in court is a hygrometer box test! You also need photo evidence of reading with a Qualified whitness statement to the readings. There is no way in the world they have been to court using a piece of plastic and a protimeter reading! LOL.

You will not get a correct reading! The box test or plug test is protected from air temperature change and without the protection you can get false reading due to condensation ect. You will be able to get an idea of what it is but it will not be correct.

Also when was the protimeter last calibrated? If you have been told info like above i guess it may not of been calibrated in a long time! To calibrate you are going to have to send the protimeter off. So as a quick test to save yourself the hassle i would nip into a shop that sells hygrometers and compare the protimeter to there readings. This is not the correct thing to do but will give you a idea in case it is not working correct.

Your reading of 67% is high but about correct for a room that has a wet slab in there. Is your heating on? this will help dry the floor!

The reason you have to get the floor down to 60% is so that the moister in the concrete is about the same as the moister in the air. If they are to far apart then the one side of the wood will have different moister to the other side. This will cause cupping of the floor. If the moister is really high in the floor then the wood will suck in so much and expand at far to fast a rate, which will cause the floor to fail. If you dont want to wait for the floor to dry then you could use a surface DPM. But this is extra cost.

 

[scottylowe]

OK guys! I appreciate that the moisture meter may not be recently calibrated but its all I've got so please bear with me.

I have done 3 tests over the past days and the RH has varied dramatically.

In the room the figure has varied from 45-75% and the figure below the plastic sheeting(taped down with thick DUCT tape) has varied from 60-90%.

So both measurements have changed by almost 30% Today was pretty humid here. However the difference between them has been around 15% at most.

i.e when it was 90% below the sheet, it was about 75% in the room. and when it was 60% below the sheet, it was about 48% in the room.

Do you think that this 15% difference is still too much? I imagine this would be the difference between the moisture on the top of the wood and the bottom of the wood.

The floor was laid 7 weeks ago and I have had a dehumidifer running most nights with the doors open on days when the weather is nice to get the air blowing through.

Thanks, Scott

 

[mattysupra]

the moister in the room will be lower after the concrete slab has dried out, so ignor that at the moment. I think you need to buy the correct plugs so you can take the correct reading of the floor. Your plastic method is not working if it changes that much. You can get a change of 10% between two readings if big changes of temperature and air humidity.