MatthewPike

New concrete floor screed needs tiling

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Hi People,

 

I have a problem, long story short we laid a new concrete floor (a week ago) in the kitchen we are renovating (30m2)... all to building regs insulation membranes etc etc. Now the problem is I need to get the tiled floor down or my wife will have my guts for garters. So my solution is as follows.

1, Prepare concrete floor inc primer and pour self levelling compound MAPEI ULTIMATE LEVELLER 1210 SELF-LEVELLING FLOOR COMPOUND ( this is my area of concern as the floor will continue to shrink below) I'm aiming to only hit the low spots with this rather than a complete surface but not sure how doable this will be in practice.

2, Lay Ditra matting adhering to SLC with ARDEX AF 200 PLUS  (I'm hoping this will allow the concrete floor to continue to dry out and the shrinkage will not affect the tiles)

3, Lay Ceramic tiles with flexible tile adhesive. Kwik Flex Grey Floor Tile Adhesive

 

No underfloor heating as i'm too tight my wife says and I say that's why slippers were invented.

 

Any other solutions greatly received.

 

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Get an industrial dehumidifier and get it running ASAP. Floor moisture level needs to be dropped but move the unit around so you don’t dry and crack one area. How thick is the screed..??

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9 minutes ago, MatthewPike said:

Hi People,

 

I have a problem, long story short we laid a new concrete floor (a week ago) in the kitchen we are renovating (30m2)... all to building regs insulation membranes etc etc. Now the problem is I need to get the tiled floor down or my wife will have my guts for garters. So my solution is as follows.

1, Prepare concrete floor inc primer and pour self levelling compound MAPEI ULTIMATE LEVELLER 1210 SELF-LEVELLING FLOOR COMPOUND ( this is my area of concern as the floor will continue to shrink below) I'm aiming to only hit the low spots with this rather than a complete surface but not sure how doable this will be in practice.

2, Lay Ditra matting adhering to SLC with ARDEX AF 200 PLUS  (I'm hoping this will allow the concrete floor to continue to dry out and the shrinkage will not affect the tiles)

3, Lay Ceramic tiles with flexible tile adhesive. Kwik Flex Grey Floor Tile Adhesive

 

No underfloor heating as i'm too tight my wife says and I say that's why slippers were invented.

 

Any other solutions greatly received.

 

Don’t use Ardex 200 onto concrete 

It’s for sticking the matting to timber 

Use flexible tile adhesive with a 6 mil notch 

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26 minutes ago, PeterW said:

Get an industrial dehumidifier and get it running ASAP. Floor moisture level needs to be dropped but move the unit around so you don’t dry and crack one area. How thick is the screed..??

understood, 100mm.

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As Peter has already pointed out 

You must get the moisture content down in the floor, If it’s not dry the tiles will lift

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100mm would normally take 100 days to properly dry (and cure) so you have a while to wait. Ideally you shouldn’t get the moisture out too quickly as it will weaken the concrete - force drying after 14 days should be ok if this is only a screed but it will still take at least another two weeks with a dehumidifier to get it anywhere close to acceptable. Forcing it too quickly could also make the slab curl so be very careful and move the dehumidifier about. 
 

How big are the dips and humps that you need to use SLC..?

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On 17/11/2020 at 07:37, PeterW said:

100mm would normally take 100 days to properly dry (and cure) so you have a while to wait. Ideally you shouldn’t get the moisture out too quickly as it will weaken the concrete - force drying after 14 days should be ok if this is only a screed but it will still take at least another two weeks with a dehumidifier to get it anywhere close to acceptable. Forcing it too quickly could also make the slab curl so be very careful and move the dehumidifier about. 
 

How big are the dips and humps that you need to use SLC..?

up to 10mm in a couple of places.

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So to get SLC to flow properly, @Nickfromwales advises to get the floor sopping wet and then mix the SLC “like mother’s milk...” so an extra 6-700ml of water per mix. I would get this done now and then leave it 72 hours and start with the dehumidifier 

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Sopping wet with a mix of ( 25% ) flexible tile primer and ( 75% ) water to ‘size’ the new screed. 
Then a 50/50 mix used on a sponge to re-dampen the screed literally done as the flexible tile adhesive for the Ditra goes down. That’ll be bombproof. You should not lay tile adhesive onto a biscuit dry floor. 
The Ditra will indeed prevent the tiles from being affected, and should give up to 10mm decoupling (  @nod ? ). 

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On 16/11/2020 at 22:50, MatthewPike said:

Now the problem is I need to get the tiled floor down or my wife will have my guts for garters.

 

Sounds a harsh woman to please! When I did my bathroom.....

 

Main slab - Feb 2016

 

Wet room corner slab - April 2018

 

Tiling started - August 2018

 

😉

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3 hours ago, Nickfromwales said:

Sopping wet with a mix of ( 25% ) flexible tile primer and ( 75% ) water to ‘size’ the new screed. 
Then a 50/50 mix used on a sponge to re-dampen the screed literally done as the flexible tile adhesive for the Ditra goes down. That’ll be bombproof. You should not lay tile adhesive onto a biscuit dry floor. 
The Ditra will indeed prevent the tiles from being affected, and should give up to 10mm decoupling (  @nod ? ). 

If the floor is still drying it can still lift Even with Ditra 

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4 hours ago, Onoff said:

 

Sounds a harsh woman to please! When I did my bathroom.....

 

Main slab - Feb 2016

 

Wet room corner slab - April 2018

 

Tiling started - August 2018

 

😉

Was the slab dried out by the time you started tiling ?

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4 hours ago, Onoff said:

 

Sounds a harsh woman to please! When I did my bathroom.....

 

Main slab - Feb 2016

 

Wet room corner slab - April 2018

 

Tiling started - August 2018

 

😉

UFH on when? 

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Just now, Gav_P said:

UFH on when? 

2024

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43 minutes ago, pocster said:

2024

Sporty! Highly ambitious too I’d say. 😁

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5 hours ago, Onoff said:

 

Sounds a harsh woman to please! When I did my bathroom.....

 

Main slab - Feb 2016

 

Wet room corner slab - April 2018

 

Tiling started - August 2018

 

😉

 

I envy you guys that just crack on with it... I let things drag on and on. 

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@MatthewPike

the solution to this same problem that I’ve used a lot on fast-track commercial projects is using a liquid surface applied damp proof membrane:

https://ardex.co.uk/products/damp-proof-membranes/
it slows the moisture movement from the slab down to a level where it no longer causes a problem to the final floor finish.

....but it’s not a cheap solution.

Edited by Ian

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