Old adhesive

[timnuttuk]

Hi,

I know that most advice is to remove old adhesive from the walls before re-tilling, but I'm struggling to get it off. Softening it with a steamer helps, but still a tough job. My question is, why bother removing the old adhesive if it's stuck fast - the tiles won't fall off....will they?

Second question, is on one wall the sandy coloured concrete seems pourous, and well....sandy. If I run my hand over it, I get a layer of sand on my hand - not lots, but I'm worried the adhesive won't stick. Should I seal it before hand and if so with what?

Thanks
TimN

[wine~o]

The reason for removing the old adhesive is to get as flat a surface as possible...nothing to do with adhesion..tiling over a lumpy surface would be a bit like trying to do a 5000 piece jigsaw puzzle on a pincushion.(Sorry not the best analogy..) you are never gonna get it flat

[Rookery]

Are you sure the wall surface is concrete? It sounds like it might be render or it might be gypsum bonding coat. Render is a good surface to tile onto but bonding is not.

[timnuttuk]

How can I tell? It's about 2cm thick and it is covering the dark grey breeze block. I've chipped some of it off to fit the shower tray. It's a light brown sandy coloured material that the old tiles were stuck to.

Does that sound like render
Thanks for the replies so far!
TimN

[royaloakcarpentry]

Probably best to whack a nice clear picture in here for us because some peoples brown render is actually a dull shade of pink bonding plaster lol. That way we can be sure and advise correctly. If it is external wall then it is probably render.

[timnuttuk]

In the pic, you can see the old shower, with a couple of tiles still stuck. Below the shower is the white addy, and the brown(pink ) sandy stuff...

It's an internal wall (upstairs), but it's a 1980s house, so no partition stuff, all solid internal walls.

TimN

[royaloakcarpentry]

Looks like render to me and the fact it has been tiled directly onto would reinforce that fact, especially as those tiles have been up a good few years.

As advised, adhesive needs to come off, be skimmed over with plaster, or bagged tile adhesive if small areas.

If you skim then walls need sealing with coat of PVA allowed to dry then another coat of PVA and then skimmed when tacky. PVA needs to be watered down.

If you use bagged tile adhesive to feather out areas then it needs priming first.

Again as already advised, prime before tiling with primer that is recommended by the adhesive manufacturer. I would use and recommend a bagged adhesive. Bal, Mapei, Nicabond.

[timnuttuk]

OK thanks all!