Help! There has been some confusion over whether we can seal our slate tiles as our screed has been only laid for 5 days, would it really be a problem sealing the tiles as we can't grout till the tiles are sealed/stain stopped. What problems would be encountered if we seal it and the screed hasn't dried????
Would appreciate answers very soon
Thanks
Martin
The advice I had from several sources when a screed was laid in my conservatory on top of a concrete base was to wait a week after the oversite concrete before screeding and then 3 weeks after that before laying slate.
You should really wait before laying the slate, never mind about sealing. Curing of the screed is mainly a chemical process, but if you are too fast off the mark in laying the tiles, I understand from a professional who did that there is a risk of the slates either lifting or cracking.
It's a case of being patient.....
.andy
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Thanks for your reply Andy. Unfortunately the slate was laid today! We received advise from Stonell that it be OK to lay the slate on the screed after only a few days as long as we don't seal them. From that advise I assume their reasoning is that they think that screed gives out moisture and as long as the slate isn't sealed and grouted moisture will be able to escape from the screed allowing it to dry- is this totally incorrect? Can we claim from Stonell if the tiles crack later? Help!!!!! Also the instructions on the adhesive and it says 3 weeks should be allowed before tiling after screed is laid! Is Stonell right or everyone else!? My builder is intending to stain stop the tiles and grout tomorrow should I tell him to wait????
Thanks
Martin
I'm surprised in a way, because they supplied my slate and were one of the sources of advice to wait three weeks. Oh well.
the curing process is predominantly a chemical one rather than a drying out one.
My concern is that the moisture has been removed from the screed artificially and the curing may not complete properly. I believe, but would need to check, that with a dryish mix like a screed, that the risk from too rapid drying is that it can crack or in the worst case crumble.
I think that that would be tough.
Three weeks is undoubtedly a conservative figure and you may get away with less.
It probably is not going to make a huge difference at this point. If the room has been artificially dried then most of what moisture there was will have gone.
I suppose what you could do is to leave the slate unsealed and ungrouted for the moment and cover it with paper or something to protect it for a week or so. Then see what happens and go from there.
.andy
To email, substitute .nospam with .gl
What is this screed? How thick is it? Those I've used to a depth of half inch you can walk on in 3-4 hours with no risk of subsequent cracking. Expensive stuff over a large area though.
None.
Screed sets as much as dries.
Slate is more or less impervious anyway. The grout will slowly leak moisture out, even if 'waterproofed'
Nothing will be harmed by having a higher floor moisture content under a semi-impervious layer, for a year or two till it all equalises :)
That IS true. My screed cracked - quite badly in places - and shrunk. That took a few weeks
Cracks can be filled believe it or not - by pouring gallons (lioterraly) of diluted PVA down them. That stabilises the screed and prevents movement.
Then use a reasonably thick bed of slate cement.
what is equalising??? :(
Thanks for your reply Andy. Unfortunately the slate was laid today! We
I think teh greatest danger is not the dampness of the screed being unable to escape, but the danger of the screed shrinking and causing loose slates etc.
I would satin stop it immediately, but hold off grouting a week or two. If a slate crack or lifts, you can replace it fairly easily. (Car body filer is a superb tile ahesive BTW, just ***ing expensive....)
1/2" aint a screed. thats a skim!
Screed is generally 3-4" You can walk on it after about 24 hours, but full strength and shrinkage builds up over a week or two.
Sorry - mean that the screed and the room humidity levels reach equilibrium.
Look never mind the damp under the slate. Its probably a Good Thing to slow the drying out of the screed anyway. The greatest danger is laying slate over an unstable structure. Or getting staining on the slate due to damp migrating upwards. But I doubt that.
I reckon you will get way with it, but, as I said last post, maybe delay teh grouting a few weeks in case a slate comes unstuck, or cracks.
Well, there's a source of confusion then. Screed in the flooring trade these days refers to the self levelling variety, which is applied to a max depth of half inch. Excellent stuff for bringing old concrete floors up to standard quickly but too expensive for levelling.
Mm. Screed in the building trade is not. That's just a self levelling skim.
I'd say your floorers have hijacked the wrong word.
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