Advice Needed On Surface Preparation For Tiling

[K73]

Hello,

I've started a major DIY renovation of my bathroom and would like some advice on how to proceed as regards preparing the walls for tiling. To help understand my question I've attached some photos of my bathroom.

All the internal walls of my house are solid, light-weight concrete and it appears that they were plastered onto with a coarse plaster where the old tiles were and in the areas that are painted finishing plaster on top of that. I've removed the 'airing-cupboard' to add extra space into the bathroom and will block up what was the door for the cupboard with plasterboard. In the area where I'll be putting the shower I'm going to seal it with something like Dunlop shower waterproofing.

It's my intention to completely tile the bathroom but this is where my problem is. You'll see in the photos that the old tile adhesive is still on the wall and it's pretty rock-solid. I'm obviously going to have to plaster the exposed concrete blocks (this was where the old bath had been) but I'm after some advice on what to do about the areas with the old adhesive.

• Do I chisel off as much of the old adhesive as I can?
• Can I use new adhesive over the old stuff?
• Should I remove the loose adhesive and then skim the surface with plaster or can I just do the same thing with tile adhesive as I'm fixing them?

Your advice and help is appreciated

[davemulheran]

You want as smooth a surface as possible for finally tiling on to.

I personally would remove ALL loose adhesive and reskim the walls

Then once fully dry, prime the skimmed surfaces with Mapei primer G, then get tiling!

Dont forget to tank the substrates in and around the shower area before hand

[K73]

You want as smooth a surface as possible for finally tiling on to.

I personally would remove ALL loose adhesive and reskim the walls

Then once fully dry, prime the skimmed surfaces with Mapei primer G, then get tiling!

Dont forget to tank the substrates in and around the shower area before hand

Thanks davemulheran,

Since making my post I've come to the conclusion that because I've knocked a wall out too and some blocks are partly expose it's probably better to get the old plaster off and start from scratch i.e. back to bare concrete blocks. HSS do chipping hammers that would make this easier I'm just worried about damaging the blocks underneath though.

I was told I could then tile direct to the concrete blocks but looking at the mortar in the already exposed blocks it's not even. I though it might be best to bond plasterboard in the not-so-wet areas to the wall and backerboard (wrong term?) for around the shower area. I've got the added 'problem' that where the shower will be is where the old doorway for the airing cupboard (I knocked out) was.

[davemulheran]

I wouldnt start chiping anything away if it is solid. A good plasterer should be able to skim over a rough surface as long as the protrusions/cavities are not too great.

Another scenario is to reboard the entire area. Use plasterboard for non wet areas (dont get skimmed) and use a cement based tile backer board to do the wet areas. You will be limited to a certain weight of combined tiles/adhesive/grout on a plasterboard/skimmed surface I believe, so look in to if you are using large tiles.

For example I am building a wet room and am using 12.5mm marmox boards instead of plasterboards. These are waterproof and perfect for laying tiles on. See here http://www.marmoxboard.com/en/index.php ... ion-boards