gyvlon floor and I am the bad boy!

[Gazzer]

So i am starting a gyvlon floor today but the hygrometer says 85%.
I tell the client that it is too high and he goes ballistic at me. I explained all about the issues and what needs to be done when tiling onto these floors and he seemed to understand. Now i am getting blamed for any delay..... The facts are that he didnt decide he wanted tiles until last week. Today is the first chance i have had to check the floor. My thoughts were to sand the floor and check moisture
So he either sees that i am working to spec or i reckon he will have to get someone else.
50m2 of failed porcelain sounds expensive to me.

 

[DHTiling]

Use gypfix , you can tile at 85% RH then.

 

[Gazzer]

The info i had for gypfix said 75% ??? If 85% is ok then everyone will be happy. I was using gypfix anyway.

 

[Gazzer]

As usual Dave. You are right......dunno where i got 75% from ?
Happy days again.

 

[DHTiling]

75% with cement based addy

 

[Skyline]

Hi, don't know if this link helps but it looks like they do mention 85% RH...?

ncdirect.co.uk.co.uk/pdf/gypfix.pdf

 

[Gazzer]

When i left the job last night the hygrometer had gone down to 83%. Happy days i thought and now i can crack on with the job. well this morning i arrive and check the hygrometer which has been in place overnight.......94% !!. Now to explain to mr angry !

 

[jonnyc]

ive had this problem as well where reading showed 76 one day and got ready to start and went back up to 85 overnight. used the ball box and still in same place.
drives me nuts these screeds but i wont take the risk.
ive seen two failures very recently ( not my own )and can be very expensive to put right if kitchen on top and needs removing to relay floor.

 

[Gazzer]

Exactly my thoughts Jonnyc. Too much of a risk for me.

 

[Ajax123]

Three things spring to mind

How long was the floor box left on the floor before reading the moisture? The usual reason for this happening is tha the. Is has been left too long on the floor and it has built up a micro climate inside the measuring chamber underneath. They should usually be left for no more than 72hours. Any longer than this and you get interstitial condensation problems such as those you are seeing.

The other other thing that can cause itis if the box is read to soon. They should really be left on the floor for indium 24 hours to reach equilibrium. Unfortunately the ball ones say read after 4 hours. This is not lon enough. The reason for this is that we are dealing with such low moisture contents. It takes a while for the chamber to equilibrate. So you ge a reading of say 85% at four ours which tells you there is moisture there but not how much (typically it wold be aout 1% which is next to other) then it is left overnight and the system equilibrates to 92% (whichis about 1.5%) moisture. Throw n a few temperature and atmospheric variables and the whole thing is upskittled. If it is below 75% itis much drier at aout 0.3 to 0.5% and responds more slowly to atmospheric changes.

So with floor boxes it needs to be minimum 24 hours maximum 72 hours. If you have not read it within this time it will not be accurate.

If itis below 85% ( not 85% or below!!) then it could be tiled with one of the gypsum adhesives althoughi would always take two readings personally to corroborate each other one at 2 hours and a second at 48 hours.

Of course as I said three things spring to mind... The third is that it might simply not yet be dry...

Clear as mud I know... Ay wpquestions see me after the lesson.. 🙂