Hi All,

Your guidance please.

Im going to be fitting some 10mm thick porcelain tiles to my bathroom.

The wall tiles are 50x600 and 100x600. 75% of the walls are plasterboard which has been sealed, the other 25% is a really well bonded glazed ceramic tile which id like to go straight over. This wall behind is a cement screeded wall unlike the others.

The floor tiles are 300x600. Im laying an underfloor heating mat laid over F Balls Flex 700 and a couple of coats of Thermacoat.

So - any suggestions on the right adhesive that would cover all this? Ive looked on the Bal site, Ardex site etc but could do with some expert help.

Also - any thoughts on a 200watt underfloor heating system as opposed to a 150watt system? The underfloor heating will be 3m2

Thanks in advance.

M

hi Mike, for your walls I'd use Mapei Keraquick adhesive, same for the floors but with the latex plus additive to give it more flexible properties

Thanks Doug ! Thats brilliant.

One other thought - should the glazed ceramics be scuffed up in any way or simply cleaned and dry?

I missed the bit about over tiling, best to remove existing tiles Mike, due to safe weight bearing issues

Hi Doug,

The existing glazed tiles are well stuck to a cement wall. The new tiles will weight 24kg/m2. Could I not scarify the tiles, prime with something and then install?

M

Hi Mike, your new tiles are going to be heavy enough on their own, putting them over the old tiles will exceed weight limits, they may look nice when finished but what if they fail?
A little extra prep now will give you total peace of mind, I would take Doug's advice mate and remove them.

Definitely good advice there. That much weight means you should def remove the old ceramic tiles; more work involved but worth the effort for sure. You'll get a better fix and most importantly, peace of mind that no-one will get killed or injured by falling porcelain tiles.

Thanks everyone. Looks like i'll be getting my lump hammer and bolster chisel out. That'll please the wife.

Once all removed can I leave a slightly scruffy background (so dont have to skim), prime and then fit new ?

Also - on the other walls which are painted plasterboard. Sand to remove paint, prime and then fit new ?

M

If you mean new plasterboard Mike you can dot and dab that into position, this will cover up any bad surfaces. If the walls being replaced are going to be exposed to water then use aqua panels or similar.

deffo don't skim Mike, is the substrate sand and cement render? hopefully it is and not a gypsum coat ie browning/bonding coat. Use a sander to try and remove the emulsion from your plasterboards, prime with an acrylic primer and use a cement based (bagged powder) adhesive

Cheers Doug. Not sure about the base behind the tiles. I guess i'll find out in a week or so when I remove.

Is the Keraquick still OK on plasterboard once primed as well as the new wall?

it is fine Mike, it's quick setting so only mix up smallish quantities at a time, don't be talked into buying tubbed adhesive, it's no good, especially for the tiles you'll be fixing

I can heartily recommend Mapei Keraflex Maxi if you're not too confident with a quick setting adhesive. It'll last in the bucket for about 8 hours

Thanks again !

Finally - the wall tiles by the bath and within the shower enclosure - I was looking at Mapei Primer S to the walls before fixing the porcelain. OK?

How about Mapei Flexcolour as the grout for all the walls (including shower enclosure) and floor?

If you are tiling inside a shower enclosure then I would use a tanking system/kit, if it’s already boarded out. As a primer (acrylic not pva) will help your tiles adhere to a wall, but will not seal the shower wall from water ingress as a tanking system does. It’s a little extra expense, (between £40 - £90ish) but if you are doing your own job you are saving money anyway, so might as well do it right first time!
Most of the leading adhesive manufacturers make them, I believe Mapei make Mapegum wps with mapei wet room kit, but I haven’t used theirs before, so not sure.
Below is a link to Weber’s tanking system, you don’t have to use their system but it gives you a good idea what I am referring to.

Tanking systems - Weber, world?s leading manufacturer of industrial mortars for the facade, tile fixing and construction markets
Totally agree with previous comments on keeping weight to minimum on walls by removing the old tiles first in this instance. Don't forget your safety glasses when chiselling them off though, you wanna be able to see your finshed job!