Curing cement before laying ceramic tiles

[Suz]

How long should cement cure before laying ceramic tiles? Screed is going down today. There will be underfloor heating if that is an issue.

Want back in house before Dec 19... wah....

Suzanne

[Andrew Gabriel]

Cement takes 4-6 weeks to reach final set (and needs to retain some moisture during this period, not enough to feel wet, but I wouldn't artificially heat it).

I would leave it as long as you can. Probably don't need full set just for tiling, but if you do it too early, I think you risk the tiles pulling away with the screed surface. (This is probably more an issue of when you start using the floor, than when you lay the tiles.)

[boltmail]

1 day per mm, officially (thats for sand/cement, rather than pourable screed which sets much faster).

The way around it is to use Schluter Ditra matting as an intermediate layer between the green screed and the tiles. Flexi adhesive under and over the matting. More expense, but you can tile as soon as it is firm enough to stand on and gives you a shot at your Christmas ambitions...

[meow2222]

can it not get tiled after you move in?

NT

[The Natural Philosopher]

Only enough so that any cracks that appear can be filled with PVA, or that was my experience anyway.

Strictly you should let it dry out thoroughly - weeks - but it will simply slow the evaporation rate from the screed by tiling it. ince te cement you will uses is pretty wet anyway, I wouldn't regard that as a major issue.

You might want to hold up grouting it though.

But really, the best tiled and DPM'ed screed still has some form of path to air, even if its a very slow one. It will dry out eventually whatever.

I would lay off heating it for a few weeks though. To let the strength build.

[The Natural Philosopher]

It's well worth dousing the floor with PVA before tiling. As much to kill any surface dust as anything.

[boltmail]

Having said that, here's another cheaper one (tile after 7 days):

http://194.223.92.131/pdf/Technical%20Data%20Sheets/B%20&%20C%20Technical%2=0Data%20Sheets/BAL_Green_Screed_Adhesive.pdf

[boltmail]

Don't do this if the floor might get wet. Use SBR if you want to prime it, not PVA. PVA is a bad idea in this application. You end up gluing the tiles to something that turns into a squidgy mush if it gets wet, which is pretty dumb thing to do when the screed itself is a much better substrate.