New screed meets UFH

[Al@Lifetiles]

Hello all.
just a quick question. How long is it advisable to leave a 75mm sand/cement screed before installing electric heating cables and latex?
Thanks in advance.

 

[Ajax123]

Till it is dry. If it is a straight forward sand cement screed unmodified then you will be looking at approximately 3months. Ie 1mm per day.

 

[Al@Lifetiles]

Well that was what i thought as well.
So if i told you a builder was screeding a conservatory today with a view to laying the heating cables on Monday and latex on Tuesday....
Seriously.
There is a guaranteed failure but what will actually happen?
Many thanks.

 

[Ajax123]

Well that was what i thought as well.
So if i told you a builder was screeding a conservatory today with a view to laying the heating cables on Monday and latex on Tuesday....
Seriously.
There is a guaranteed failure but what will actually happen?
Many thanks.

I would sayif he is doing that he is a fool and the installation is bound to fail.

There will be a numberof events. Firstly the latex is unlikely to stick properly because of the vapour pressure exerted bythe water in the screed trying to get out. Thiswill cause a delamination event. Secondly the screed will shrink and crack causingnthe latex to crack as wel and also another delamination event.
thirdly the screed will curl again causing cracking and delamination. All these things will gang up on him and the floor will eventually fail.