Tiling uneven floor

[Mike S]

I've used some latex self-levelling compound to even out a concrete floor prior to tiling. Unfortunately the surface hasn't ended up as flat as I was hoping, with ridges left in some places where the flow ended. I had to pour the self-levelling compound from two different corners of the room (because of a slight hump in the middle of the room plus a rise in the third corner) and was unable to get things to marry up cleanly in the middle. The result is somewhat disappointing, I have to say.

I've laid some tiles out without adhesive just to see how flush they fit to the floor. Alas, in many cases there is a bit of wobble present rather than even contact across the whole surface area of the tile. Can I deal with this by varying the thickness of the tile adhesive or do I need to get the floor 100% flat before tiling, perhaps by pouring another coat of SLC?

I'm reluctant to do the latter, in case I end up with same problem as before and because the stuff is expensive. I’m tempted to see what I can do with the tile adhesive - if the worst comes to the worst and I end up with one or two cracked tiles I can always replace them - they're only cheap ones and I have quite a few spares, and it's my own property and I'm not moving out in a hurry. How quickly would a failure in a particular part of the tiling become evident and how easy is it to replace a cracked tile should this happen?

Any suggestions would be much appreciated.

Thanks,

Mike

 

[jctilingservices]

I've used some latex self-levelling compound to even out a concrete floor prior to tiling. Unfortunately the surface hasn't ended up as flat as I was hoping, with ridges left in some places where the flow ended. I had to pour the self-levelling compound from two different corners of the room (because of a slight hump in the middle of the room plus a rise in the third corner) and was unable to get things to marry up cleanly in the middle. The result is somewhat disappointing, I have to say.

I've laid some tiles out without adhesive just to see how flush they fit to the floor. Alas, in many cases there is a bit of wobble present rather than even contact across the whole surface area of the tile. Can I deal with this by varying the thickness of the tile adhesive or do I need to get the floor 100% flat before tiling, perhaps by pouring another coat of SLC?

I'm reluctant to do the latter, in case I end up with same problem as before and because the stuff is expensive. I’m tempted to see what I can do with the tile adhesive - if the worst comes to the worst and I end up with one or two cracked tiles I can always replace them - they're only cheap ones and I have quite a few spares, and it's my own property and I'm not moving out in a hurry. How quickly would a failure in a particular part of the tiling become evident and how easy is it to replace a cracked tile should this happen?

Any suggestions would be much appreciated.

Thanks,

Mike

It would depend on how far the floor is still out mate, if you are only talking a few mill here and there, using your addy to make up the defecit would be ok. try putting a level or straight edge over your floor, this will tell you how much you are out BUT double check to make sure you have no high spots, You dont want to start getting your tiles down only to run into a high spot, then ya got to start chiselling it away, making your work more harder

You cant really put a time limit on tiles cracking, just remember to twist the tiles as you bed them into the adhesive, or you could even spread your adhesive then back butter the tiles at the points where you are low

 

[Richard C]

Unfortunately the surface hasn't ended up as flat as I was hoping, with ridges left in some places where the flow ended.

Why not remove the ridges!

I've laid some tiles out without adhesive just to see how flush they fit to the floor. Alas, in many cases there is a bit of wobble present rather than even contact across the whole surface area of the tile.

The fact the tiles wobble on a bare floor is not a meaningful at all; you need to establish how much your out;
a) over the whole floor &
b) on, say a 1 ½ mete by 1 ½ metre basis but it depends on tile size

Can I deal with this by varying the thickness of the tile adhesive

You can to a certain extent & if you’ve experience at doing it but if you haven’t, it may be asking too much of your skills & the tiles could end up all over the place. For floors you should be using a quality trade cement based adhesive & a solid bed, thick bed trowel & this will give a typical adhesive thickness of around 4mm; but it can be used to fill out up to 12mm locally.

or do I need to get the floor 100% flat before tiling, perhaps by pouring another coat of SLC? I'm reluctant to do the latter, in case I end up with same problem as before and because the stuff is expensive.

Difficult to know how critical your being about the floor without seeing it but my advice would be to get the floor a flat as possible over, say, 1 ½ metre increments even if that mean having another go at the SL screed. This stuff usually works very well so it sounds as if you may have not got that quiet right 1st time around. A big factor is also the size of the tiles you’re laying; large format tiles (anything over 300 x 300mm) require a very flat tile base or you’ll get serious lipping & it will look the pits when finished.

I’m tempted to see what I can do with the tile adhesive - if the worst comes to the worst and I end up with one or two cracked tiles I can always replace them - they're only cheap

If tiles start cracking, you’ve got it very wrong. A solid bed adhesive is a must for floors, please tell me you weren’t thinking of dot & dabbing them!

 

[jctilingservices]

Richard
How do you do that, quote someone but then have it broken down into individual paragraphs, it makes answering someone much easier that way

 

[Richard C]

Richard How do you do that,

Easy

quote someone but then have it broken down into individual paragraphs,

Just copy & paste the quote paras at the begining & end of each bit you want to answer individually.

it makes answering someone much easier that way

Like this - but I've put an additional - at the end quote bracket so you can see what I've done

Richard How do you do that, [/quote-]

quote someone but then have it broken down into individual paragraphs, [/quote-]

it makes answering someone much easier that way
[/quote-]

 

[jctilingservices]

Richard How do you do that,

Easy

quote someone but then have it broken down into individual paragraphs,

Just copy & paste the quote paras at the begining & end of each bit you want to answer individually.

it makes answering someone much easier that way

Like this - but I've put an additional - at the end quote bracket so you can see what I've done

Richard How do you do that, [/quote-]

quote someone but then have it broken down into individual paragraphs, [/quote-]

it makes answering someone much easier that way
[/quote-]

i will give it a try the next opportunity i get mate, cheers Richard

 

[Mike S]

.. if you are only talking a few mill here and there, using your addy to make up the defecit would be ok. try putting a level or straight edge over your floor, this will tell you how much you are out BUT double check to make sure you have no high spots...

I'm not out by that much.. 2-5mm depending upon where I measure from.. but the floor is only 2 x 2.5 m2 overall. The problem is the shape of the floor.. although only visible when a batton is placed across it, it rises to a sort of hill in the middle, dropping down to three of the corners, but rising up again to the fourth corner. I'm not too worried about the fourth corner as it will have a shower tray on it with adjustable feet so I can deal with height differentials that way and won't have to tile all the way into the corner anyway (and even if I do any lipping will not be visible, and bedding them down properly will presumably prevent any cracking).

I've tried lowering the central hill a bit with a scraper, but am still a bit out. Also, having scraped off the top mm or so of the SLC which is super smooth, underneath it's quite rough and leaves a white chalky residue on your finger, even after being swept clean.. is that to be expected from a latex based SLC? I guess, whatever I do I'll have to prime that before adding adhesive or another layer of SLC.

Any more thoughts or comments are again most welcome.

Thanks,

Mike

 

[Mike S]

Can I deal with this by varying the thickness of the tile adhesive

You can to a certain extent & if you’ve experience at doing it but if you haven’t, it may be asking too much of your skills & the tiles could end up all over the place. For floors you should be using a quality trade cement based adhesive & a solid bed, thick bed trowel & this will give a typical adhesive thickness of around 4mm; but it can be used to fill out up to 12mm locally.

The stuff I have at the moment is Unibond all-in-one adhesive and grout.. also looks like it is thinset 3mm.. I guess from what are saying I should return it and get something different?

please tell me you weren’t thinking of dot & dabbing them!

Not quite sure what that is, but assuming you mean putting a blob of ahesive on the tiles and sticking them down like that. No, I was intending to lay them on a proper bed using notched trowel etc.

Thanks again for comprehensive reply.

Mike

 

[Richard C]

The stuff I have at the moment is Unibond all-in-one adhesive and grout.. also looks like it is thinset 3mm.. I guess from what are saying I should return it and get something different?

God don't use that stuff, only really fit for the nearest skip The good stuff don't come cheap BAL, Webber, Mapei (not the one stocked by B&Q though) etc. but you can get good prices if you bully for a discount or shop around.

Also, having scraped off the top mm or so of the SLC which is super smooth, underneath it's quite rough and leaves a white chalky residue on your finger, even after being swept clean.. is that to be expected from a latex based SLC? I guess, whatever I do I'll have to prime that before adding adhesive or another layer of SLC.

Don't prime unless recommended by your adhesive manufacturer & then use only an acrylic primer; use a flexible cement based adhesive over latex based SLC.

Not quite sure what that is, but assuming you mean putting a blob of ahesive on the tiles and sticking them down like that. No, I was intending to lay them on a proper bed using notched trowel etc.

Good man but you need a thick bed solid bed trowel; 20mm round notches, 10mm deep, at 28mm centres.

 

[Mike S]

Thanks Richard, I guess I should go for a Mapei adhesive then as the SLC and (acrylic) primer are from them. I'll take the Unibond back to B&Q.

Cheers,

Mike