Matt emulsion paint as primer for plastered wall before tiling?

[Riker007]

I've never heard of the above method being used. I was told by an experienced builder that this is what to use. Basically 3/4 of the plasterboard walls were taken off, new plasterboard put up, then had a skim of plaster to match up to what part of the walls wasn't taken down. The plaster has had a week or so to dry, and it was literally a skim to even up the walls. Now from what I've read, people are saying different things. The tub, yes tub of ready mix adhesive (super grip stuff recommended to use by large tiling company - who also have a fleet of their own tilers) says on the back can be applied straight to plastered walls.
Anyhow, the builder has painted the walls with matt emulsion. I'm the one who is going to tile it all, and have previously had difficulties when it comes to old emulsion paint on walls. So now it has had a fresh coat of emulsion onto the plaster, is that perfectly okay or does the surface just need scratching up before tiling? I want to able to sleep at night...

 

[nybor62]

i would sand it off , some emulsions will wash off

 

[Deleted member 9966]

get rid of the emulsion paint on the plaster skim. like Rob says above, sanding will get it off or you might be able to scrub it off with a wet sponge if it's just cheap paint. buy a suitable tiling primer (not PVA or paint) to apply over the sanded plaster skim and you'll be able to tile from there.

out of curiosity, what size tiles are going on the walls?

 

[Stewart]

I would remove the paint and call this so called "experienced builder" an idiot. You need to prime the walls with the recommended primer to suit the adhesive (NO PVA). What size of tile are you putting on top of the skimmed plaster as there may be a weight issue and tubbed gear is not recommended for large format tiles.

 

[Del W]

As above

 

[finlay]

all good advice as above

 

[Riker007]

Well the tiles are 300x450, a little large for tubbed adhesive but the tiling place guarantees it will work perfectly and have no problems, its the same stuff they always use, and the tiles were bought from them , they've been in business for 40 years so I guess the tubbed stuff will be fine.
I popped in to speak to them about the emulsion problem, both their resident tiler and a visiting tiler both agreed that if I were to scratch the walls up properly, then sanding it all off won't be necessary. So my dilemma is:

a. sand it all off, then prime it with the official tiling primer stuff.

b. scatch it all up, tile straight onto wall, either with or without tiling primer.

Option A is obviously the best option, but as long as the tiles aren't going to fall off ever, then option B. Or option C?

n.b Is there not primer stuff already mixed in with adhesive?

 

[Del W]

how thick are they

 

[Riker007]

Tiles are 8mm thick, ceramic...

 

[DHTiling]

The adhesive is unsuitable for that format of tile no matter what the shop says.. 300x300 is the max size for a dispersion adhesive..

Use a standard set cement based adhesive and after paint removal prime the walls with an acrylic primer to prevent reaction with the adhesive.

As for the builder.... his excuse so he can get on with the painting i guess.. but deffo wrong advice just like the shops.