Hi there I'm looking for some tips for my Kitchen floor project...

Floor is T&G Chipboard floating floor, it creaks a little but no visible deflection. I'm planning to overlay with 12mm ply and screw every 200mm or so.

I have 405x405 12mm thick Star Galaxy Black tiles to lay but I'm most unsure about is which is the best adhesive to use.

Sorry if this has all been asked before but I've read a lot of posts already and the more I read the more confused I am. I was thinking to use one of the BAL products as they seem to have a good reputation (and used already fro some wall tiling) but which one? should I use one of the single part adhesives eg Single part fastflex? Single part Flexible, Rapidset Flexible, OR the 2 part Fastflex? I'm really confused since all seem to be compatible to what I need to do and there's no obvious choice.

Depending on the adhesive I also need some advice on how it should be applied ie size of notched trowel or solid bed thickness req'd etc.

Advice from someone who's done this type of job before would be really appreciated. Thanks.

Is your floor 'floating, (on insulation say) or screwed down on joists? If it's floating then it's a no go until you sort your floor out. Nice tiles and a shame to waste them

Chipboard is over timber joists

Originally Posted by mlinn

Chipboard is over timber joists

Ok that is different, you have a suspended floor not a floating floor.

Due to the nature of the tile you are laying, it is a good idea to make your floor as stong as possible, granite is a dense heavy material and you will be several dozen if not hundres of kilo's extra loading to your joists (how big is the floor?)

12mm ply may not add sufficient strength to cope with the load so you may be better opting for 18mm WPB ply instead. This should be screwed at a max of 300mm centres, half that would be better. make sure you seal the underside and edges first before screwing down. BAL recommend BAL Bond SBR for this. No need to prime the tiling surface.

A flexy rapidset would be fine if you lay 18mm but if anything less you need to use an S2 class adhesive such as Mapei Keraquick with lates plus or Bal Fastflex. Mapei is cheaper and easier to work with.

Originally Posted by grumpygrouter

Ok that is different, you have a suspended floor not a floating floor.

Due to the nature of the tile you are laying, it is a good idea to make your floor as stong as possible, granite is a dense heavy material and you will be several dozen if not hundres of kilo's extra loading to your joists (how big is the floor?)

12mm ply may not add sufficient strength to cope with the load so you may be better opting for 18mm WPB ply instead. This should be screwed at a max of 300mm centres, half that would be better. make sure you seal the underside and edges first before screwing down. BAL recommend BAL Bond SBR for this. No need to prime the tiling surface.

A flexy rapidset would be fine if you lay 18mm but if anything less you need to use an S2 class adhesive such as Mapei Keraquick with lates plus or Bal Fastflex. Mapei is cheaper and easier to work with.

Agree with the above, i used Mapei Keraquick on Black galaxy on a few jobs had no problems.

Keraquick is an excellent adhesive....

I would not consider anything other than 18mm ply when using granit on a suspended floor, purely because of the combined extra weight of the tile, adhesive and grout.

Firstly absoloutly make sure that the floor is solid and as deflection free as what is humanly possible, (trust me it's worth the extra work now), Prime the underside and sides of you ply with an sbr primer prior to fixing and then for me, screw your 18mm ply down at no more than 150mm centers and preferably 100mm centers.

Fix the tiles with MAPEI KERRAQUICK flexible cos this is a fantastic adhesive and then make sure you grout with a fleible grout.

Take you time and if you get stuck come back and ask again.

OK so MAPEI KERRAQUICK + Latex Plus it is then. I suppose this is preferred to the ULTRAFLEX S2 MONO single part adhesive because of the much shorter ready to use time?

Now a couple of other things that come to mind..

What thickness do I need to use? and What size notches should my trowel have to achieve the corrrect thickness?

Also is there any need to "back butter" the tile, as I've read this is required for large tiles and if so why is that required (mine are 405x405 and obviously being natural stone are flat backed)?

Thanks for all the help so far..

10 mm radius notched trowel. If you skim the back of the tile with the flat edge of the trowel, this ensures that the adhesive is binding fully with the tile as opposed to just 'on the peaks' of your adhesive troweled on the floor. Also, if your tiles are dusty the back buttering overcomes this as well.

I thought I was clear with the adhesive to use Keraquick + Latex but is this sensible for a novice? I like to take my time and I'm worried this adhesive will go off too quickly for me. Is there a slower setting / standard equivelent S2 adhesive that will have a longer open and pot time??

OR should I stick with Keraquick & Latex and just mix small quantities as I go?

Finally, about the correct trowel. does it make a big difference to use a 10mm radius(rounded pattern) trowel or 10mm notched (square pattern).

Thanks