UFH Liquid Screed - Cracks

24 Mar 2020
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United Kingdom

I have had my existing floor screed dug out (over block and beam) throughout the ground floor of my property and UFH and a new screed put in. The screed has been poured about 4 weeks ago and the UFH has only just this week been commissioned on its lowest temperature (manifold outlet temp about 18 Degrees).

I have noticed a couple of cracks have formed in the screed, one is in a doorway between two rooms and a second one is in the kitchen/diner room, which is a large L shaped room. The crack appears to come from the corner of the 'L' and radiate diagonally towards the outer corner (See attachment, but not to scale). The crack does not fully reach the other side of the room, however.

In both cases, the cracks are all but hairline. They are smaller in width than a credit card at their widest part. The screed appears stable on both sides and no difference in height can be seen. The screed has a foam strip around its entire length and all interfaces with walls etc. The floor build up is 100mm insulation, vapour barrier, UFH pipes clipped into insulation, 50mm screed. There is zero movement through the screed.

When the screed was laid, the screeders spent quite a bit of time vacuuming the vapour barrier around all the pipework to remove all loose material so i am happy it has been laid properly.

What i would like to know is;

* - Is this normal and something that is to be expected? The 'L' Shape room is approx 10M long along its longest side, by approx 6.5M wide so quite a large pour. Does any remedial work need to be done or should this just be left if nothing else happens?
* - In terms of tiling, how long should be left before tiles are laid? It has been a month already but i want to ensure that the screed is entirely stable before tiling occurs. Are there any other recommendations for tiling etc.?



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