Matt emulsion scraping off wall, what's going on here..

[fixo]

I'm in the process of preparing a room for decorating and noticed that some of the existing matt emulsion on the walls (applied by previous owners) can be scraped off relatively easily (some places not so easily). See video here

The walls are paramount boarding with a plaster skim but seem to have a yellowy coating beneath the paint that is scraping off. The property is a 1990's build so I don't believe the coating is distemper paint (which I've had the displeasure of dealing with in previous properties). I've attached a close up photo of the surface beneath the matt emulsion. It's slightly dusty to touch when first scraped, but after wiping it remains dust free.

Any ideas why the existing white emulsion scrapes away from the wall in this way?
I'm loathed to prepare (sugar soap, thorough rinse, diluted first coat) and paint them without scraping it all off or stablising somehow because the last room I worked on in this property I prepared the walls, then applied 2 coats of silk emulsion which, when dry, peeled away with fingers in a stretchy rubber-like film including the matt emulsion layer that was originally there. Any ideas/thoughts on this? Thanks in advance

 

[JohnD]

is it a kitchen?

If you wet it with a sponge, does it bubble?

is the older paint silk?

 

[fixo]

It's a small bathroom, the previous room with paint issues was a bedroom. The walls have a white matt emulsion with the yellow coat of something below. I've applied a steamer to it with a scouring pad, the matt emulsion comes away quite easily with that and the yellow substance goes washy like a dust/chalk and rubs off..

 

[blightymam]

Few things going on and maybe a few reasons?

Sometimes a chalky residue can be got from old paints, I wonder if that may be the case? If it wipes off and that's the end of it, I would suspect that's all it is.

Matt paint painted over a more silk paint may not adhere that well.. Could be why it's scraping off so easily.

I also wonder if the walls were mist coated with PVA originally too, another reason the original paint isn't sticking when you gave it new coats.. In your photo, the plaster looks too clean to have had a good mist coat with paint.

 

[Tigercubrider]

I have just spent all of August trying to redecorate my through lounge.

I started in the dinning area and had exactly the same issue.

I came to the conclusion that it was old wallpaper paste that hadn't been cleaned off.
I used a window scraper and yours comes off easier than mine bloody did.

I ended up sanding areas that were revealed yellow after paper removal, some was steamed off, and sugar soap and foam centred sanding blocks used for the rest. Total pita.

It must have been put on with a trowel, some areas were really thick with it

 

[Robbie uk]

Another surface that could benefit from a coat of Zinsser Gardz. This would seal the surface prior to further coats of paint.