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Concrete Floor levelling


Ron Avery
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Trying to make an entrance hall out of what was a cave for keeping goats or calves.  The concrete floor is very rough and uneven with a dip in the centre from the edges of up to 5cm. Any ideas on the best method of levelling this floor for laying floor tiles.  I have thought about but ruled out tiling straight on the floor with very thick tile cement in the centre but is that an option?  Would a thin skim of mortar do the trick or would that be too thin at the extremes?  The floor can be raised by any amount so a thick levelling coating is not a problem.  Are there any products in France that can be easily applied for this?  Thanks in advance
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Ron, you need a chape (aka screed en anglais). 

That is, a layer of sand and liant laid not too wet, minimum thickness say 5 cm.  Get the liant from a builders merchant (a mixture of cement and lime). Proportions of the mix are usually stated on the bags of liant.

Not sure of the area, but set up level lines around the perimeter or use level rails made from wood set at the finished level and use a straight edge to 'pull' the chape. You can embed gaines in your chape if you need to.

If the results, once it has gone off, are iffy, don't worry, you can buy ragreage form the buliders merchant to cover your sins. It mixes into something akin to custard (remember custard?), you pour it on to your chape and it sets dead level.

Then you tile using ciment colle (source as above). Don't even think about using tile cement of varying depths...you'll be sorry...

Does this help ?

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Bring it up to reasonable level with a screed of sand and cement, not forgetting to key the existing surface very well. If you don't, then pouring new mix on an old surface it could move. No bond.

Then use a self-levelling floor screed which is a two pot mix, powder and fluid. This self-levels.

Then the tile fixative.

That from my best chum who runs a large commercial flooring company: and what his guys did on a two shop-to-office conversion for me a few years ago, where the floor surface was awful and after the dividing walls were removed the levels were all over the place.

 

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Ron, if using the two-part self levelling stuff to finish off:

 mix it thinner, rather than thicker than the instructions.

Once it's hard, use a straight edge to remove any obvious tiny humps, there almost always are some.(Easier to find and remove them now than when your tile won't lay flat[;-)])

Apply PVA or similar to the surface to seal it BEFORE tiling.

FA

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Thanks, I'm a little confused now as to why I need a  sand/cement screed and then a self levelling screed.  Can't I just put a self levelling screed on top of what is there or are there thickness limitations with this stuff?  Bearing in mind it will be tiled over and any minor imperfections dealt with by a little more tile glue.

The area to be covered is L shaped 5metres x 2 metres then 1 metre by 2 metres.

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Usually the self-levelling applications states a  maximum depth of 8/10mm , certainly a lot less than the 50mm you quoted on your original post.

Its quite difficult to get a perfectly level floor , especially one of 12 sq metres , and the others are anticipating this.

However if you make a half-decent job then as you say you can make up for it with a variable depth of tile adhesive.

By half-decent I mean fluctuations of less than 10mm.

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[quote user="Ford Anglia"]Ron, if using the two-part self levelling stuff to finish off:
 mix it thinner, rather than thicker than the instructions.
Once it's hard, use a straight edge to remove any obvious tiny humps, there almost always are some.(Easier to find and remove them now than when your tile won't lay flat[;-)])
Apply PVA or similar to the surface to seal it BEFORE tiling.

FA

[/quote]

 

just a small point ....never use pva on a surface prior to tiling ....only ever use manufacturers recommended tile primers if the surface requires it.....all manufacturers guarantees on adhesives are voided if surfaces are sealed with pva as this will eventually lead to a breakdown of the bond......it seems to be a common misapprehension that pva is a universal stick everything type building adhesive, but not when it comes to tiling i'm afraid...hope this helps

 

sheldon

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Ron:

As Northender states, over 12 sq M that's quite a vast area, unless you are doing this day in and day out. Like plastering a small patch is not too hard but 12 sq Ms of wall is a demanding task.

The Self-Levelling screed works because it "Flows". There's no magic in it: gravity pulls it out as you spread it and it flows enough to reach a common level with a little bit of help from the user!

That said, to mix sufficient for 12 sq Ms is quite a task in itself!

With a reasonable wet mix of sand and muck, at least you can spread it evenly before it starts going off.

This is not a job for the fainthearted!

Best of luck.

 

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Ron

You need a screed (chape) to level it.

If you are expert you can get the chape dead flat and 'nickel', then you can lay the tiles direct, you don't even need glue if you are up there with the pros.

However, in the real world.....

pull a chape, well dosed with liant and not too wet, panique pas if it is not brilliant because you always have recourse to the magique self levelling gung....but it is very expensive and that's why prof. carreleurs don't use it or need it.

Above all don't try variable thickness glue/ciment unless you like sticky mucky wonky disasters !

You could always try your local carreleur if your courage fails...best answer if you are not sure and if the result needs to be 100%.

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This thread is very interesting to me because I have the same problem as the OP in what will, hopefully, become a bathroom. I have been looking for some time for a levelling compound but didn't know what I was looking for. Now I do - so thanks. PVA was mentioned. This is something else I have been looking for and have yet to find. what name does it go under in France?

Patrick

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[quote user="sheldonrobbo"] never use pva on a surface prior to tiling ....only ever use manufacturers recommended tile primers if the surface requires it..... [/quote]

 

Can anybody tell me a brand name of such a tile primer please?  ..... something I could get in Bricomarche or similar....... I was about to use PVA  [Www]

 

Thanks

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Racking my brains I cant remember the material we got instead of PVA but it was brill its  a stabiliser for patch mortar repairs I think but did the trick.

RE PVA it's not intended as a stick all or a coating to provide a smooth surface to substrates or a waterproofer (all common misconceptions) it's best used fairly well diluted as an agent to be absorbed by the substrate the idea being that it reduces suction from the substrate and allows the tile adhesive time to set up properly and form a bond.

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[quote user="newbiee"]

[quote user="sheldonrobbo"] never use pva on a surface prior to tiling ....only ever use manufacturers recommended tile primers if the surface requires it..... [/quote]

 

Can anybody tell me a brand name of such a tile primer please?  ..... something I could get in Bricomarche or similar....... I was about to use PVA  [Www]

 

Thanks

[/quote]

Newbiee,

Look no further than www.weber-broutin.fr  Their stuff is available in lots of places. More in tile shops and builders suppliers than Brico shops. There is a list of suppliers online.  They do a very comprehensive catalogue with detailed advice. Sadly, I find the catalogue interesting reading.

The primers are here and here

They are not as cheap as others but you only want to do it once

Danny

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  • 1 month later...
Thought I had best mention this upoon re-reading. This all rather assumes that the cave floor is a viable concrete slab or screed a beaten earth or cobble floor may want a bit more thinking about. My Cave floor (Currenty a mish mash of earth and concrete) is going to be an Insulated RC slab, I am very tight for headroom and I don't want to undermine footings. so its 200mm well consolidated hadcore blinded with 25mm sand, 1200 guage DPM turned up the face of the vertical studded wall membrane 50 mm Jablite then a 150mm RC slab. We will use a laytex screed once the dry lining is in then install an electric heating matrix under tiling. Entire floor make up inc tiling about 450mm but a job intended to last and the configuration of the vertical DPM Running to the same formation as the hard core will allow any dampness from the walls to travel freely without affecting the living area.
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I had a garage with a rough  concrete floor  converted to a bedroom 7 years ago-area23sq.metres by an english  self trained builder.

I WAS VERY SURPRISED WHEN HE SAID HE WOULD LEVEL IT WITH EPOXY TWO PACK ,

 AS I WAS A  PAINT CHEMIST IN UK AND FORMULATED THESE PRODUCTS WHICH WERE NOT ON SALE TO THE GENERAL PUBLIC.

He made an excellent job so gluestick reommendation of  a screed and when dried out the appliation of self levelling epoxy would be the best long term solution as no fear of breakdownetc.

 

 

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