To back-skim or not to back-skim?

[Brad]

Hi all....

Firstly, thank you to all involved for answering my many questions. This is a very good forum to be on. Keep up the good work, Dave and the team. I would not hesitate in recommending this forum for both new and experienced tilers.

I am still looking for a definitive answer to the following question:

Taking into account the strength of an adhesive to adhesive bond and considering the non-porous nature of PORCELAIN tiles, is it good practice to ALWAYS back-skim PORCELAIN tiles, regardless of their size? Or is this overkill?

 

[Time's Ran Out]

I'd think that the larger the size the greater the need to ensure 100% coverage of adhesive. However your adhesive choice is also an important factor as some adhesives are aimed for large format tiles and it flows to a level to allow the maximum support required. And then again with mosaics the right sized notched trowel will provide the correct preparation without back buttering.

 

[Brad]

Thanks John. Maybe if I phrase my question this way.....

Considering the non-porous nature of porcelain, would it be good practice to trowel the wall and do nothing to the back of the tile (Given that the wall is straight and level, of course)?

 

[Alan.P]

On a wall I would back butter, on floors we normally use a pourable thick bed ( ptb ) the nature of this adhesive means that there is no need to back butter / skim, always good practice to lift a tile or 3 along the way, just to check, you would be surprised.

 

[Time's Ran Out]

Thanks John. Maybe if I phrase my question this way.....

Considering the non-porous nature of porcelain, would it be good practice to trowel the wall and do nothing to the back of the tile (Given that the wall is straight and level, of course)?

NO.
The wall may be flat and level:lol: but the back of the tile may not. You must fill all the voids before the coming together.

 

[Perry]

On a wall I would back butter, on floors we normally use a pourable thick bed ( ptb ) the nature of this adhesive means that there is no need to back butter / skim, always good practice to lift a tile or 3 along the way, just to check, you would be surprised.

Alan not sure I have ever seen you not lift a tile up I sure last time you done a floor you lifted every tile up on what was it 400 mtrs lol

 

[Tony73]

allways back butter all tiles, porcelain, stone etc. not mosaic

 

[bugs183]

Due to the non porous nature of porcelain no adhesive even if if mixed slightly wetter will be absorbed by the back of the tile like ceramic tiles. Therefore you have to back butter to make sure the adhesive is covering the whole of the tile to get the best adhesion possible.

 

[Dan]

allways back butter all tiles, porcelain, stone etc. not mosaic

That would get messy!

 

[Muse2k8]

I'm trying to imagine the fun back skimming mosaics

 

[Brad]

On a wall would you back butter even smaller PORCELAIN tiles? (thinking of bugs183 comment below)

 

[Brad]

Thanks bugs. Based on what you have said, do you back butter even smaller sized tiles? (obviously not mosaics) And would you do this for ceramic as well as porcelain?

 

[Alan.P]

Alan not sure I have ever seen you not lift a tile up I sure last time you done a floor you lifted every tile up on what was it 400 mtrs lol

Only when you weren't looking lol, sure your exaggerating a touch there though maybe half of them

 

[Tony73]

That would get messy!

Why Dan?

 

[Tony73]

i don't back butter tiles smaller than 200x250, or masaic

 

[Ian]

Why Dan?

I think Dan was referring to back skimming mosaics only, not the other tile types

 

[bugs183]

in theory you'd back butter all tiles, ceramics can absorb any moisture quickly and therefore could debond, and porcelain doesn't absorb anything and could debond too because you are totally relying on the polymers in the adhesive to stick to the tile, bit of a weird one when you think look at it.
I tend to back butter all porcelain, big, small, walls and floors, just to be on the safe side. As for ceramics, i don't back butter walls as a rule, but it is a good idea to back butter floors and wet areas, as there is a mechanical key to the tile when buttering, and it means you have fresh adhesive touching adhesive when the tile is fixed to the floor.
It doesn't take to long to do, and a belt and braces approach is better than going back to sort problems

 

[Brad]

Thanks Bugs. Good thread. I would imagine tho that if the PORCELAIN tile is small or the the wall/tile is straight and not bowed, that back-skimming would suffice as opposed to back-buttering?

 

[swanman]

Back butter every thing

ALWAYS

 

[Brad]

don't think it's always necessary to back BUTTER everything. back SKIM.....yes.