Best adhesive for tiling over tiles?

[Tony 1]

Hi, i'm sure this as been asked many times but i cannot find the answer through various posts. I am going to re-tile my bathroom with 30 x 60cm tiles. My bathroom is mainly studded walls and to take off the existing tiles i will cause too much damage to the walls so i wanted to tile over them. What is the best adhesive to use as they are big tiles and whats the best method to prep the walls prior to tiling?

Thanks

 

[PaulTheTiler]

If you are using 60x30 tiles then you really need to re-think. Tiles that size are normally made of porcelain or a much denser than normal ceramic biscuit. Either way, they have very little absorption. As the existing ceramic tiles have no absorption either, the adhesive has no-where for the moisture to go and can therefore never dry!

Add the weight factor of your new large tiles and you are asking for trouble.

I would advise stripping the old tiles off. If the plaster board is too damaged, it's really not that difficult to put up new plasterboard.


Paul

 

[Richard C]

Sometimes it’s unavoidable but tiling over tiles is not a good solution at any time & I'm with paul 100%; with tiles that size/weight, you definitely need to rethink it or it'll probably end in tears. If it’s just stud partition, pull the lot off & start again, it’s not as difficult as you might think; only use Moisture Resistant plasterboard in bath/shower rooms but in wet areas you should tank or use a waterproof tile backer board.

Make sure you do some reasearch on tiling materials as well; the tiling sticky is a s good a place to start as any.

 

[Tony 1]

Is it because of the size/weight that i cannot tile over tile even i stagger the joints or is because its porcelain onto ceramic so the tile won't stick, or is it a mixture of both?

 

[lancenotalot]

What you need to consider is the weight.What is the wall they are fixed to?
Bonding and skim,plasterbrd and skim.
Recommended weights are

20kg per sqm for plasterbrd and skim or bonding and skim
32kg per sqm for plasterbrd with no skim.

 

[Richard C]

The surface of the existing tiles has virtually no absorbtion & it can be difficult to get the tiles to grab & stay in place. Small light tiles are usually OK but consider the weight of the large tiles you’re proposing to use & you should get some idea of the problems you may have getting them to stick & stay up there long enough for the adhesive to set.

The most important thing to consider is that plasterboard will only take a total weight (tile, adhesive & grout) of 32 kg/sq m unplastered; plastered it drops to 20 kg/sq m. Yours is already supporting one tile layer, add to that the possibility the PB may not be in good condition under the existing tiles & there is a real possibility the whole lot will collapse. I don’t know how much your paying for your tiles but add onto that the cost of decent trade flexible adhesive & grout (don’t attempt it with cheap DIY shed crap) then the additional cost a of a few sheets of MR plasterboard & a tanking kit is not much extra to pay in order to guarantee the success of your tiling project; do you really want to risk it!

If you do decide to risk it, prime the surface first with an APD primer & use a single part flexible or Rapidset Flexible adhesive; don’t risk tub mix. I would leave it for at least 5 days before grouting.

 

[Tony 1]

Magic, I've took your advice and started removing the tiles and the plaster board has damaged so i will remove all that as well. When i replace the plasterboard and its ready can i use a ready mix adhesive to fix straight to the plasterboard?

 

[Richard C]

You should seriously consider using a decent tile backer board rather than plaster board, it’s far more suitable for the inside the shower cubicle. The cost difference between the two is marginal once you factor in the cost of tanking which you should do if using Moisture Resistant plasterboard.

Don’t use tub mix for tiles of that size & weight, it’s not really up to it; use a quality trade flexible powder adhesive & grout. You can tile straight onto backer board or tanked plaster board.

 

[Tony 1]

Should i use Bal primer on the new plasterboard when its put up?

 

[Richard C]

Are you tanking the PB or are you going to risk it? Either way, use BAL prime APD under WP1 or Rapidset Flexible.

 

[Tony 1]

I was going to leave the area at the bottom of the bath tiled as i just have a shower over the bath. My reason for this is because the boarding behind the tiles is the old type asbestos boarding because my boiler is on the other side of the bathroom wall. The new tiles at the bottom of the bath are going to be mosaic tiles so i thought i would be able to tile over the original tiles.

 

[Tony 1]

Final question as you have all be very helpful. I am thinking of using Gran Fix Fastset Flexible cement based adhesive with their Acrylic Bond and Primer prior to tiling. Is this ok? Is a 3mm bed thickness good enough if i also back butter the tile and what size notched trowel do i need to use.

Thanks again to everyone's advice, hopefully i can do a nice job with the help i've received from you all.

Cheers