wall preparation

[Cath]

Hi everyone. In process of having bathroom improved (shower installation over bath) and i will need to do tiling around bath myself due to budget restrictions. Need advice please!
New tiles are 24.5 x 19.5 cm and about 5mm thick. I have purchased Bal White Star adhesive and Bal SBR primer. It is a downstairs bathroom in old cottage.
When i removed the old tiles (which were only on lower area) quite large sections of thin plaster skim came off with them. I chipped away until all loose sections appeared to be off. (Areas up to 100cm x 50cm). Underneath appears to be rough sand/cement type surface. I then filled in these areas with patching plaster but am not happy with it. It appears very soft and crumbly. I think i should remove this and repatch with something stronger? What should i use please? (Plasterboarding is not an option due to it already being a very tight space). I need to get the existing wall surface in a suitable condition to take the tiles securely. Would really appreciate your advice.

 

[Boggs]

Can you post a few pictures for us please, we can then better advise. 🙂

 

[Cath]

Hi, Boggs, and thank you. Here are 2 pics of one end, first was pre patching and second is after. Hope this helps.

 

[J K Tiling Cornwall]

When you say you filled in with a patching plaster was it already mixed in a tub or powdered? If already mixed might just need a little longer to cure.
The surface behind the plaster is a cement render. Ideally I would have primed that with some dilute SBR prior to filling over. Thanks

 

[demi34]

Powder adhesive is much w, but you have to use primer first

 

[Cath]

Thank you both. It is Bartoline patching plaster (powder) applied over a month ago. Substrate was just wetted not primed, as i was advised to do, and only apply primer over this top layer, prior to tiling. So much conflicting info! Anyway i think i will remove the filler as i am not confident of it's strength given it can be scratched with a fingernail. Is there a better product i could use to fill (i've seen something called Thistle multi finish plaster that appears similar but not sure?) or would it be better to do as a friend has advised and just use extra tile adhesive on those areas? My concern about that is that the Bal white star recommends a max depth of 3mm and the bare areas are already a depth of about 1 or 1.5mm, and also whether i would manage to get the area level enough, doing that.

 

[Boggs]

I would remove the filler back to the cement render, prime the whole area with 2 coats of sbr primer, then when dried skim the areas needing filling with a standard setting cement based adhesive, like Tilemaster Setaflex.
When it’s set prime over these again and fix the tiles using the same cement based adhesive.

 

[Cath]

I would remove the filler back to the cement render, prime the whole area with 2 coats of sbr primer, then when dried skim the areas needing filling with a standard setting cement based adhesive, like Tilemaster Setaflex.
When it’s set prime over these again and fix the tiles using the same cement based adhesive.

Ok thank you Boggs. I have already bought a large tub of Bal White Star adhesive, would it be ok to skim with that?
Re the SBR, what are the dilution ratios i should use?

 

[acaciaguy]

Hello Cath. You would be better skimming with a cement based bagged adhesive - such as the one Boggs suggested. I wouldn’t skim with tubbed

 

[Cath]

Hello Cath. You would be better skimming with a cement based bagged adhesive - such as the one Boggs suggested. I wouldn’t skim with rubbed.

Ok thank you. I'll look for standard set Setaflex.
What dilution ratios for the 2 coats of Bal SBR primer, please? Or just neat?
(What is 'rubbed', btw? 🤔)
Thank you for your patience, complete novice here and anxious to get it right.