Large Format Tile Adhesive - some queries!

[leighduffy]

Good Afternoon and Merry Christmas everyone, and congratulations and thanks for a very informative forum adn excellent research for all things tiling; both professional and novice.

I have read the forums with great interest over the past weeks as I begin to embark on two DIY tiling projects in my bathroom and ensuite. I was hoping I might trouble some of the more experience and informed amongst us to cast a quick eye on my plans in the hope I you may be able to enlighten me as to how suitable my plan is and any problems I can expect....



I have opted to use Mapei Keraflex Maxi adhesive for my wall tiles which are upto 300x600mm in size as many of the ready-mixed tubs specified max tile sizes of 300x300. The wall tiles will be tiled to plastered/plasterboarded stud walls, plywood boxed sections and plastered/rendered masonry walls and also used in showers. I have purchased Mapei Plaster primer and wondered if the plywood required/would benefit from any pre-treatment or primer? The Mapei Keraflex Maxi Tech Data states that it has a pot life of 8hrs with an open time of 30mins.... would somebody mind explaining the difference between these in terms how much needs to be mixed up at a time, as some of the definitions on other posts are a little confusing!



I have also purchased Mapei flexible grout and when reading the Tech Data Sheet to determine consumption I noticed that there was no entry for 2mm grout widths for 300x600x10mm tiles, the thinnest was an entry for 3mm. Do I take this as me being unable to use 2mm spaces on tiles of this size? I am sure I have seen some modern looking large format tiles with very thin grout lines in other places (hence my idea for this!) but if this will likely cause an issue I am unaware of I will increase the width.

Also, in terms of aesthetics I have some mosaic tile sheets to use as features which may have a slightly wider spacing on the gauze sheeting - in your experiences is it best to match the spacing of all tiles so they are consistent with these mosaic spacings, or could I get away with still picking my preferred main tile spacing and the difference with the mosaics would be lost to the eye? (Mosaics are approx 20x70mm.)

Am I correct in understanding that joints to internal corners and floor/ceiling should all be siliconed rather than grouted, to allow movement?



Finally, I am also to be tiling porcelain and ceramic floor tiles 450x450mm onto well-screwed-down Weyroc floorboards (*after much consideration!*).... For this I am using Topp Fix 2-part flexible adhesive but am struggling to understand how trowel sizes/shapes correlate to adhesive bed thicknesses. I believe I need a 6mm bed for the floor with 3mm for the walls and the tiles also being 'back-buttered' (just a thin adhesive covering pre-applied with straight trowel to back of tile to ensure 100% coverage - is that correct?).... but how does this correlate to the tools themselves: notched or half-moon and which size???


Sorry to bombard you guys with questions on my first post, but whilst I have some DIY tiling experience with cheap tiles / poor products I really want to make a success of this as it is my new home so want it 'tiled-to-last' with the satisfaction of achieving it myself to a good standard, so wanted to consult some experts before embarking on the project to give me every chance to make a success of it!



Look forward to hearing from some of you shortly and to getting on with the job!



Many Thanks,



Leigh.

 

[Dan]

Grout lines should be minimum of 2mm for walls and 3mm for floors. Not sure of a difference to that rule when it comes to large format tiles to be honest but perhaps there is.

Internal corners should be hollow to allow for expansion and retraction on either wall, and then the Silicon sits over the surface to cover the small gap and to finish off the job looks-wise. So you're only putting the Silicon on the surface of each tile, so if you could imagine either wall moving a few mm, the Silicon would give and flex and not actually be blocking the hole which wouldn't allow the tiles to move into it - sort of thing.

I'll let the others answer the more techie questions, I haven't tiled for years myself.

 

[beanz]

I can't give you any advice on the Mapei products, as i don't use them..

2mm spacers should be fine, but a lot depends on your choice of tile.. Tiles do vary in size and squareness (especially cheaper tiles), so you may need to adjust the size of your groutlines as you work. No need to match the grout lines with the border imho.. Don't Silicon between the tiles and ceiling, as this will cause you problems when you come to paint the ceiling.. I usually just grout it, but you could use caulk if you wanted.

With regards to pot life (amount of time it will stay useable in the bucket), and open time (amount of time it'll be ok on the wall, waiting to be tiled).. I usually start by putting about an inch of water in a gorilla tub (for adhesive), mix it up, and see how it goes.. Mix the grout in small amounts.. It goes off pretty quickly!

 

[Rookery]

Keraflex Maxi is fine for your wall tiling. Prime surfaces with Mapei Primer G. Mix approx half a bag of adhesive at a time, approx 2.5 ltrs of water, it will stay useable in bucket for most of the day. 2mm spacers are ok but 3mm gives you more flexibility. Check the weight of your tiles. Plastered surfaces have a weight limit of 20kgs per m2 in BS. I wouldnt worry about the differing joints between your field tiles and mosaics.
I wouldnt use Toppfix 2 part and definitely wouldnt tile direct to chipboard.

 

[leighduffy]

Good evening all and thanks for your early responses...

Dan, thanks for the detailed clarification of the siliconed expansion joints, I will be sure to use this approach. Also with regard the grout line thickness I would agree with you that there is no lower limit for thickness, as I have certainly seen very large tiles with very thin grout lines.... the Tech Data did not specifically forbid this but I was curious as to why the value was ommitted - perhaps as the grout consumption was so low so did not specify a figure?

beanz thanks for the advice re caulking and for the definitions of the powder lives, which will greatly help when mixing up; thanks also for the heads up on the Grout! Our tiles are not cheap, ceramics sourced from local builders merchant £15+VAT on bulk-order, and Wickes £15 per m2 so hopefully reasonably accurately manufactured.... only time will tell!!

Rookery thanks for the advice on preparing mixes, and I will reconsider the 3mm if it has additional benefits. Would you mind explaining where the additional flexibility stems from with 3mm vs 2mm spacers - is it because the Grout allows more movement when set than the adhesive? Also thanks for the weight limit warning - our ceramic tiles are fine for plaster but the porcelain a little heavy, hence the plywood boxing first- would you recommend tiling direct to this without any treatment? With regard the direct-to-chipboard tiling, I note that this is frequently deeply discussed; many seem to oppose it whilst the adhesive manufacturer advocates it.... we are limited to ply depth to keep our floor heights the same, and were recommended that too thin a ply ( less than 6mm) would actually worsen the problem by being more flimsy than the interlocked Weyrocked - do you see any viable alternative that would maintain level floors whilst avoiding the need for this??
Thanks again for the input guys,
Best Wishes,
Leigh.

 

[Rookery]

I meant that a larger grout line will help you if the tiles are a bit sizey. IE not all the same size.
Personally I wouldnt tile to plywood, I'd replace it with plasterboard, Hardie or Marmox depending on the situation.
I know of a few 1 part and 2 part 'tile onto timber' adhesives but I still wouldnt do it that way. My way is always to overboard the floor with Hardie cement board (or insulation board if UFH), screwed and glued with Keraquick, and then tile with Keraquick. Obviously the floor must be stable first. To me its much more important to get the tile installation sound rather than worry about a few mil difference to adjacent room.

 

[Andy Allen]

good advice above, providing the floor is stable, use 6mm cement boards, this wont raise the floor to much to cause any issues..

 

[beanz]

The main reason for over boarding the chipboard IMO is to remove deflection. When your floor fails, those same adhesive manufacturers will say the failure was due to deflection (unless you're planning on ripping all that floor up, adding loads of noggins, then re-laying?), not their adhesive.

 

[DHTiling]

IMO the main reason for over boarding chipboard floors etc to stabilise the floor , chipboard is not a stable material to tile directly too , as it is a particle board and IMO isn't suitable for tiling directly to , no matter what adhesives say they can be used to chipboard..

Hardibacker is to stabilise a floor ready for tiling and this is moisture issue substrates etc and not just for strengthening as hardibacker do state that is not designed to stiffen a floor but to act as a suitable substrate that is a lot more stable to to tile too rather than a timber one.

With Haribacker being a cement board then it also gives a better substrate to adhere to rather then timber..so for the OP , do take it that hardibacker is used to stiffen floors but is a product used provide a better substrate to adhere to and does not rot or is not effected by wetting etc , unlike timber..

 

[leighduffy]

thanks for the explanation guys - i'll check out hardibacker prior to starting as I hadn't realised backer boards were available that thin.
Would anybody be able to shed some light on the trowel-size / adhesive-thickness conundrum before I start?!
Also, is the convention to tile walls then floor, to minimise mess onto new tiles?
Thanks again for the information,
Best Wishes & Happy New Year,
Leigh

 

[Rookery]

I'd use an 8mm notch trowel to stick the boards down, plus screws. I always tile the floor first but others tile the walls first and some tile the walls, leaving out the bottom row, then do the floor then fix the bottom row.

 

[leighduffy]

Thanks Rookery, and would the 8mm do the wall tiles too with the floor requiring slightly larger?
Happy New Year all!

 

[Rookery]

It should/might, depending on how flat the walls are. Comb a trial area, stick a few tiles on then remove to check you're getting adequate coverage. Its good practice to skim the back of the tiles with adhesive too. You will need a bigger trowel for the floor 12mm and back skim the tiles here as well.

- - - Updated - - -

It should/might, depending on how flat the walls are. Comb a trial area, stick a few tiles on then remove to check you're getting adequate coverage. Its good practice to skim the back of the tiles with adhesive too. You will need a bigger trowel for the floor 12mm and back skim the tiles here as well.

 

[Rookery]

It might/should depending on how flat the walls are. Its good practice to skim adhesive on the back of the tiles too. You'll need a bigger trowel for the floor, 12mm min and back skim these too.