Latex floor cracks

30 Jan 2019
Reaction score
United Kingdom

As part of our new extension our builder laid latex on top of the ufh but it’s been 2 days and there are lots of cracks appearing, see pictures attached. In some area it also cracks when walking over it. I am trying to see if this is airline crack and nothing to worry about or if it’s no good. I think I know the answer but I want professional opinion.
Fyi, we will be having lino/vinyl flooring on top.


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Was that a water mix screeding compound? ( bag only )
Looks like it to me , or a latex ( bag & bottle ) which he has added water too.
Do you know what he used?
Was the floor primed correctly?

Either way it’s got all come up and it doesn’t look bonded.
Also the sand and cement screed will need a liquid dpm as it will be full of moisture.
They did it in two stages. One layer was latex bag and bottle and second I am not sure. They used ultratilefix pro level product for the first layer but not sure about the second one and other details.

The latex was done tuesday and yesterday the plumber came to install the ugh monitor and tested the underfloor heating, he left it on for a fair bit. Could that be the issue

Is the only way to take it all up and redo?
If he’s put UfH on when the latex was drying that would crack it as rapid drying.
Is it loose when you tap it. Try get a knife under the crack and see if it lifts up.
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Some area seems loose, I can press down with my finger and it does seem loose
Do you think it needs redoing (removed and reapplied)? Is that the only way?
Yes mate that’s the only way.
If you want to take a section up. Say a few inches and send me a pic I can have a look.
Builder coming over tomorrow to check and discuss. I am going to hold on before taking a section up. I will come back to you but going over it there many spots where it sounds hollow and it seems that it wouldn’t take much to remove
The sand and cement screed should be level to SR3 and solid.
Then if needed a coat of smoothing compound with the correct primer.
Then if another coat needed prime and screeding compound again.
So where we had hollow spots we took a knife and lifted. See pictures.

Basically it seems that sort of tape they use did not stay on properly in some spot.

The tape was used over crack of the first layer. The first layer is solid though.

Builder suggest to refill where the tape was?

What are you thoughts?
Never seen tape used on cracks before.

Going back to the 1st coat. Which pro level was it he used?
How long between that and the 2nd coat. You can’t put a water mix over a latex screed as it’s a higher compression strength in most cases.
Also by the pics the water mix has been mixed with far to much water and that’s why it’s white.

Imo the top coat needs removing then the bottom coat checking.

What floor covering you having?

This is what they used for the first coat. The second coat was put 4 days after the first.

First coat seems solid as far as we see.

Apart from where there is tape the second coat seems well stuck to the first.

We are having lino put on top. Would it be an issue?

I am not sure which product they used for the second coat but I will find out today.

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