Flaky screed, day 4, normal, cement fibre stuff

[finlaand]

Hi all

Had liquid cement with fibres screed poured on Wednesday this week. Avoided walking on it and all doors ect closed for 2 days, then fx followed advice to now get lots of fresh air moving over it.

Dpm, insulation, vapour layer, then this layer, c50mm.

I walked on it earlier, and very top layer, I guess 1mm maybe less, in places a bit flaky / not set. Also odd non straight crack but they see thin.

This normal? I was told so by screed guys cracks normal, and to on day 7 even though its cement screed, still a wire brush will help over top to give a key before tiles go down on day 22.
See photos.

Maybe just me as never had this stuff before but if anything I can do now, rather than wait useful to know

 

[Swwils]

The flaky surface you've mentioned, it might be laitance, a weak, brittle layer that forms on the surface of the screed as it dries. This is usually a result of an excess amount of water in the screed mix, overworking of the screed surface during application, or premature drying of the surface. It's usually not a significant concern, but it should be removed before tiling to ensure a good bond with the adhesive. The wire brush you were advised to use is typically the tool for the job.

Remember, drying times can vary. The usual rule of thumb is a drying time of 1 day per millimeter up to 40mm, and then 2 days per millimeter thereafter. However, this can be influenced by environmental conditions such as temperature and humidity, as well as the screed mix itself. You mentioned your screed is around 50mm, so waiting till day 22 before laying tiles seems appropriate.

You shouldn't have let a draft get to it, would have minimised the cracking and laitnance.

 

[finlaand]

Actually screed guys said use a 120 groit sandpaper on top, whichb I did then swotchen to simply my hand, or short brush, akd go figure all the stuff came off, the cracks were all surface deep, now gone

One issue was where excess water settled slight discolouration and slower to dry, but covering floor untimely so not an issue...

Day 16, have moisture meter (brick one I know) and it shows 22%, and humidity is c5 degrees higher than room outside this one, ill do the taped plastic square on day 20 to see if any noticeable condensation...