flexible tile adhesive- on new floor screed

[zakrigby]

hey there guys ...ive just lay a S&c screed on my kitchen floor its around 40-55mm thick ...i was going to wait around a month before tiling over it to allow for proper drying ....but a few tilers i have phoned said they can tile straight over using flexible tile adhesive ....and assured me this will still allow the screed shrinkage and drying time ... how good is this flexible adhesive in an ideal world id love to be able to lay the tiles straight away .... but at the end of the day i still have my concerns over this flexible stuff ... and slightly more inclined to wait for it to dry before tiling.. the last thing i want to so is damage my screed ...

 

[AliGage]

Nonsense. I would be waiting about 8 weeks before looking to tile that.
Don't quite know how a flexible adhesive would allow you to tile it sooner. 24 hours per mm in depth is what I've always understood and gone with.

 

[nybor62]

as above im afraid , stay clear of the tilers who advised otherwise , you can get a green screed and do it sooner , but i would wait
there must be someone on here who is close to you im sure

 

[cam_low]

This is a new one on me ! !

1mm per day, grab yourself a tiler off here if you stick and advert up and give your location.

 

[Mark S]

Why do people want to take chances and cut corners?
Allow the screed to dry, 1mm per day unto 40mm, 2 days per mm after that.
Some manufacturers may claim that you can tile onto a 'green screed; but it won't achieve full strength till its 28 days old anyway.

 

[Ajax123]

1mm per day up to 40mm and 2 days per mm there over is the drying time. You have also laid the screed too thin. Should be a minimum of 50mm unbonded and 65mm floating. It should also be reinforced with either fibres or with d49 mesh.

 

[Old Mod]

[MENTION=12267]Ajax123[/MENTION] I could be wrong, and I'm sure I'll be put right if I'm not. But the way I understand it using a decoupling device allows u to lay tiles when the moisture in the screed is at 4% or less, 2% for calcium. Normally 2% and 0.5% respectively. The decoupling actually slows the drying and improves the chances of the screed staying stable and not curling or cracking.

 

[Ajax123]

@Ajax123 I could be wrong, and I'm sure I'll be put right if I'm not. But the way I understand it using a decoupling device allows u to lay tiles when the moisture in the screed is at 4% or less, 2% for calcium. Normally 2% and 0.5% respectively. The decoupling actually slows the drying and improves the chances of the screed staying stable and not curling or cracking.

Sort of yes. The issue here though is that the screed should be cured immediately following installation by covering with polythene for a minimum of 7days. This keeps the moisture in the screed and allows the cement to fully hydrate building up the screeds internal strength so that as shrinkage occurs (which is a natural function of cement based screeds) the stresses imparted by said shrinkage are balanced by the integral strength of the screed. All this relies on correct design, full compaction and correct reinforcement. Unfortunately in general the thinner the screed is the more propensity it has for curling, which is also natural, and which leads to vertical movement and possible deflection cracks. Unfortunately an uncoupling membrane will not offer any protection against vertical movement so in this instance I suspect it is not an appropriate mechanism to use. If the screed was cured (or the uncoupling mat placed very early) then it may be more appropriate. Anhydrite screeds do not curl and do not appreciably shrink so it could possibly be used as a moisture suppressant. In either case on relatively wet screeds the joints in the matting must be taped to avoid damp patches in the tiles.

 

[Old Mod]

Yeah what he said! Haha Thanks Alan.
I knew it was something like that.

 

[zakrigby]

thanks guys ill give it the proper 2 days per mm to dry...... i would put an add up but i'm doing it myself (only phoned round for advice hadn't found this place then lol) .... yeah just got my first house so money tight having to do a lot of work on it myself but place like this really help thanks again guys

 

[zakrigby]

1mm per day up to 40mm and 2 days per mm there over is the drying time. You have also laid the screed too thin. Should be a minimum of 50mm unbonded and 65mm floating. It should also be reinforced with either fibres or with d49 mesh.

yeah its bonded and reinforced with fibers its mostly 50mm just a small part where it needed to lay a little thin to level out.... its only a small kitchen with the units agains the 4 walls i was going to tile the whole floor then fit the units i thought id get the neater finish like this no awkward cuts round cupboards..or would i be best of not tiling rite to the back in case it curls a little on the thin part ..it will be hidden by units anway

 

[Ajax123]

yeah its bonded and reinforced with fibers its mostly 50mm just a small part where it needed to lay a little thin to level out.... its only a small kitchen with the units agains the 4 walls i was going to tile the whole floor then fit the units i thought id get the neater finish like this no awkward cuts round cupboards..or would i be best of not tiling rite to the back in case it curls a little on the thin part ..it will be hidden by units anway

When you say it is bonded, was the substrate abraded or shotblsted to form a mechanical key. I am being a little pedantic I realise so this is more in the manner of information rather than criticism. To be considered bonded it must be laid to a mechanically prepared substrate. If it is just laid on a concrete substrate it would be considered unbonded by the British Standards. If it is bonded that wlll limit the level of curling that can take place (bonded cement based screeds can be laid much thinner because of this). You also need to be aware of the potential mositure content in the substrate.

I think this is probably a case for ditra matting but will leave that up to you.

And tile up to the edges under the units as you then have the flexibility in the future to move stuff around if you want to

 

[zakrigby]

When you say it is bonded, was the substrate abraded or shotblsted to form a mechanical key. I am being a little pedantic I realise so this is more in the manner of information rather than criticism. To be considered bonded it must be laid to a mechanically prepared substrate. If it is just laid on a concrete substrate it would be considered unbonded by the British Standards. If it is bonded that wlll limit the level of curling that can take place (bonded cement based screeds can be laid much thinner because of this). You also need to be aware of the potential mositure content in the substrate.

I think this is probably a case for ditra matting but will leave that up to you.

And tile up to the edges under the units as you then have the flexibility in the future to move stuff around if you want to

no its not bonded no mechanical key ....... the only thing that was done was a hand key (chisel and hammer (inch spaced give or take ) and a cement slurry brushed on.... just read a topic on them mats will definitely be using them thanks for the heads up mate