Tiling onto uneven floor

[miksto]

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 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 to replace a cracked tile should this happen?

Any suggestions would be much appreciated.

Thanks,

Mike

 

[Andy Allen]

What make of S.L.C did you use.

 

[miksto]

What make of S.L.C did you use.

It was Mapei Latexplan Trade

 

[jay]

pics might help with a strait edge to show prob and as above

 

[thomas]

you could use floor adhesive as s.l.c its the cheaper option?

 

[White Room]

Just do the slc again over the top of the existing

 

[doug boardley]

you could use a ptb adhesive (pourable thick bed)

 

[steve j sharpe]

Hi Mike i would pour another s.l.c again on top.http://www.tilersforums.com/images/icons/icon14.png

 

[kaharrison9]

Self level again Mike.This time using the plastic packers used when fitting windows.There will be all differant thickness's 2mm,3mm,5mm,10mm etc.Find the highest point of the floor and with a long level work out where the dips are and put the correct packer under the level to get the same height to the highest point.
I put the packer on a blob of silicone to stop it floating when the slc goes down.
If a large floor say 30sm divide maybe into 3 and do 10sm at a time.Pour the slc and work it to the height of the packers.
Always have acheived a good result on very uneven floors this way.
Do check the thickness you can go with the slc

 

[Daz]

you could use a ptb adhesive (pourable thick bed)

I'm not sure if you are a DIY'er or Pro, but my experience of PTB is that it is not for the DIY'er.

I would have thought that another go with slc to take out the low spots would be your best course of action.

 

[miksto]

Thanks to all of you for your advice. Will probably have another go self-levelling. Should I prime the original layer first? I'm thinking perhaps to use a water-based slc this time, as presumably it will flow more easily. I was surprised how thick the orginal one was. It needed a lot of assistance and I felt I was running out of time before it started going off.

 

[thomas]

priming it is no harm,sounds like you mixed it to thick the last time you should'nt have to work it that much hence the name self levelling,but not to watery or it wont set.

 

[miksto]

Thanks Thomas. I followed the manufacturers instructions and added the whole batch of cement to the latex provided, so ratio should have been fine. Have been in touch with the manufacturer and they said I probably took too long mixing it and it was starting to go off. I was doing it alone and taking care not to add too much cement in one go, so despite having a drill paddle mixer it took about 20 mins to mix and was getting pretty thick as I added the final remains of the cement.

 

[tfs]

Pour in full bottle of latex, add half bag mix a bit and then pour rest of bag in (it realy is that simple matey)

Failing that get someone to pour it in as you mix.

SLC will move/spread/ level itself to an extent, it just needs a gentle brush with a trowel to help spread further.

If you have any ridges in the finnish and require the best possible flat finnish, rub these imperfections down with a carborundum stone. You will find one online easy emough if you can wait to get it delivered.

 

[tfs]

Also, if majority of floor is acceptable but you find you have a dip at one or two points, you can patch fill by targeting those small areas that may not be perfect.

I would prime the previous slc prior to pouring the additional layer.

I would go for a carborundum block with handle like this one here

http://www.carpetfittersshoponline.co.uk/carborundum-stone-rws071-23-p.asp