mapei

[dotto]

Hi guys. I have seen on the web that a 20 kg bag Keraflex Maxi Mapei cost 20 pounds plus vat.
1) is it reasonable price?
2) Is it suitable for floors and walls..... on the website they say:
-suitability: walls
-area of use: walls, floors
3) also on the bag it says: 3.15mm bed thickness......but if i use it for the floor, the thickness is surely going to be more than 3mm if i use a thick bed trowel.
4) a big section of my bathroom floor is concrete, joining a small section which also is concrete however, being about 20mm narrower in depth, the difference has been made up by putting a length of 20mm thick plywood. So, would Keraflex Maxi S1 Mapei adhesive be suitable?...i mean is it going to be flexible enough?
5) Is it ok if a buy it in white for floor and walls and then i use white grout for wall tiles and grey grout for floor tiles? Thank you very much for your pieces of advice

 

[Richard C]

£20+ for Keraflex is not a bad price but I have seen it cheaper. A thick solid bed trowel (if that’s what you have) will normally give an adhesive bed thickness of 3-4mm, which is what the info on the bag is telling you & is the minimum you need for floor tiles up to 30 x 30xm; larger really needs a large format trowel & thicker adhesive bed.

Before answering any of your other questions in detail, I need to know rather more about what you’re doing regarding size/weight/type/colour of tiles you propose; if your tiling the walls what are the walls made of & are they wet or dry areas? You have a difficult tile base with two different floor substrates of ply & concrete & tiling over them without correct prep will lead to failure. I would advise you take some time out to read the Tiling Sticky & Tiling Forum archive posts before you buy any materials or do any work, then post back additional information; it may prevent you making disastrous & potentially expensive mistakes.

 

[dotto]

hi Richard and thanks for the reply. The bathtub goes against two walls: one is plastered and the other is a stud wall. The wife wants to go for mosaics. The floor as mentioned before is partly concrete and partly ply, the tiles will most probably be white and not too big as big tiles will make the bathroom look small.I read the Tiling sticky...very useful infos! I have been on Webtiles website and i don't think i have seen Mapei S2 which is what according to you i should be using.....

 

[Richard C]

I have been on Webtiles website and i don't think i have seen Mapei S2 which is what according to you i should be using.....

Sorry forget what I said; I got my S’s & C’s mixed up & confused you (& myself ). I use BAL products so am a little unfamiliar with Mapei branding. Keraflex Maxi S1 does have a C2 classification which is what I meant to refer to. Mapei do make S2 adhesives (highly deformable as opposed to flexible) but you probably won’t need one.

Plasterboard in bathrooms should be Moisture Resistand not standard wall board but even this is not a good tile base for wet areas unless tanked; far better to use a waterproof tile backer board. Plaster also has a max weigh limit (20 kg/sqm including adhesive/grout) but this most likely won't be relevant with mosaics but check the tile weight. You can get specific adhesive for mosaics but Keraflex S1 is stated as suitable for mosaics but what are the tiles made from, ceramic glass, natural stone etc? Some tile materials are also absorbent & may need sealing depending on the colour. The colour of adhesive you use will only be important if the tiles are absorbent material & of a contrasting colour.

You still haven’t said if the ply is fixed to a concrete slab or supported over joists, how thick it is or what type it is? Ordinary ply won’t be suitable either & you need WBP. Your biggest problem is tiling over two different floor materials (concrete & wood); you will need an uncoupling membrane or it will most certainly crack where the two meet, even then it may not be ideal. If it’s a concrete base with ply fixed over it, then you would be better removing the ply & leveling the whole floor off with an SLC & tile over that.

Keraflex is a single part flexible adhesive but the spec states “not suitable for wooden conglomerates” which I take to be manufactured boards & in that case it’s probably not suitable for suspended ply floors or ply over boards. As before, I use BAL products & know them well but am not that familiar with Mapei product range, there are other Mapei alternatives (Keraquick, Rapidset Flex etc) but I advise you check with Mapei.

 

[dotto]

hi Richard and thanks a lot for the reply. The ply is fixed to a concrete slab and i can not level the whole floor off as i do not have much time to wait for it to go off. I will make enquiries about a Mapei suitable product otherwise could you advice me on a Bal product suitable for the purpose? Thanks again.

 

[Richard C]

Some SLC’s can be tiled over as soon as they are set.

For the addy, you could use either Rapidset Flexible or Single Part Flexible if you need a longer pot life but if you stick with the ply/concrete floor & don’t use an uncoupling membrane it will almost certainly crack at the join & the tiles will fail.

 

[dotto]

Hi Richard thanks for the advice.....i will have a look for a SLC of fast go off time or some addy compatible with two different subfloors. Cheers.

 

[Richard C]

or some addy compatible with two different subfloors.

No such adhesive exists; even expensive elastomeric/two part epoxy based adhesives are not a substitute nor capable of compensating for an uncoupling membrane where one is required; http://www.schluter.com/6_1_ditra.aspx
if you don't use one, your tiles will almost certainly fail.

 

[dotto]

Hi Richard and thanks for the link. My bathroom is a total of 3.5m ( length) by 1.8m ( width). The whole area is concrete apart from the last 0.8m by 1.8m which has a 25mm plywood sheet screwed onto a concrete slab to bring it even with the rest of the concrete floor. 1)The fact that the plywood sheet is screwed onto a concrete slab and not on joists, shouldn't that prevent any movement of the plywood and therefore no need of an uncoupling membrane?
2)Should i really need to lay the uncoupled membrane, should i lay it across the whole floor area or just over the plywood area?
3) What kind of thin set mortar should i use to bed the membrane?
4) What sort of addy do i have to use for the ceramic tiles? Would Mapei Keraflex S1 be ok then? Thank you very much for your time

 

[Richard C]

The fact that the plywood sheet is screwed onto a concrete slab and not on joists, shouldn't that prevent any movement of the plywood and therefore no need of an uncoupling membrane?

It’s to do with differential expansion rates of wood & concrete not movement of the ply overboard itself. You can fix the ply down as much as you want, it will still expand & contract at a different rate to the concrete, it’s this which causes it to crack & fail where the two meet. You will even get the same problem with concrete if the slab is laid in two stages or at different times, good example in this thread; //www.diynot.com/forums/tiling/cracked-floor-tiles-slab-joint.314294/

Should i really need to lay the uncoupled membrane, should i lay it across the whole floor area or just over the plywood area?

Yes an uncoupling membrane needs to cover the whole floor.

What kind of thin set mortar should i use to bed the membrane?

You can use Rapidset Flexible addy to fix the membrane.

What sort of addy do i have to use for the ceramic tiles? Would Mapei Keraflex S1 be ok then?

I would go for a higher spec adhesive, Keraquick or Rapidset Flex but you should check with Mapei; I would use BAL Rapidset Flexible or SPF.

You could still have probs even with an uncoupling membrane; personally, I would ditch the ply altogether & make up the difference in floor level with a suitable SLC, using it to cover the whole floor area & then tile over that.

 

[dotto]

Hi Richard and thanks again for throwing in the possible options. How much would a sheet of 0.8m of plywood be able to expand? If it is not much, don't you think the uncoupling membrane will take care of that little movement? At the end of the day, it is designed to do that kind of job.........unless you have heard it is not really reliable. Have you ever used it or heard any negative feed back even on such a small surface? Ta.

 

[Richard C]

I’m not sure if your question is directed at the need for an uncoupling membrane or your choice of tile adhesive. Every material known to man will expand & contract in all directions with even very minor fluctuations in temperature & with two dissimilar, adjacent materials such as concrete & wood, the difference in expansion/contraction rates will be enough to crack even flexible adhesive & grout if the range of movement exceeds the elasticity of the adhesive & grout. An uncoupling membrane is designed to allow minor lateral movement in the tile base without affecting the tiles above but weather or not it will be sufficient in your case with ply abutting concrete I can't asses over the internet & an expansion joint may be more suitable; this is why I would replace the ply with an SLC. Keraflex Maxi is classed as an S1 adhesive as are the BAL adhesives I recommended but the Keraflex data sheet states “not suitable for wooden conglomerates” which I take to be manufactured timber boards (ply). It doesn’t specify suitability for use over uncoupling membranes either so you would be wise to contact Mapei for specific guidance.

There are some in the trade who swear by fitting an uncoupling membrane over any floor weather suspended timber or concrete; belt & braces!

 

[dotto]

Thanks for your time m8