Hi all
I skimmed over an excisting ceiling a couple of weeks ago an now iv having to go back to patch it back in as the plaster has started to separate from the old ceiling in places, I put two coats of uni bond on first so I don't understand why this has happened as its never done this before. Can anyone shed some light on this on as to why??? Thanks

What did you skim onto mate? Painted plaster? Artex? Was your 2nd PVA coat sticky when you hit it?

Sounds like the previous finish on the ceiling was not porous. i.e. painted with a sheen or worse, oil based.

Take it all off and use a bonding agent if this is correct.

Are you sure the plaster wasn't out of date? The only time that has happened to me is when the plaster had gone off

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Professional Kitchen & Bathroom Fitters | Master Painters and Decorators | Brighton & Hove

I worked for a firm for a few weeks when my girlfriend got pregnant and they asked me to repair a ceiling so I went to the garage on the estate and knocked up some multifinish. I dropped the bucket trowel in and in the two minutes it had taken me to walk to the flat, it had gone solid and the trowel bounced. ALWAYS CHECK THE DATE!!!

It was a painted ceiling in matt paint and yes the second coat of pva was sticky so don't get why it happened the bag of finishe was in date.

The PVA was shite, or waterproof?

Did the paint come off?

Unibond do a special plasterers PVA which states that you can use it to go over paint (emulsion.)

If the paint has remained on the ceiling, I would use Wickes PBA before skimming again. I have never had a problem after using that stuff.

I'll give WBA a go then, how long should I let that stuff go off for before skimming over??

I think the instructions say 24 hours.

After closer inspection this morning I find that it isn't my skim coat coming away it's the previous coat coming away. So nothing to do with what iv done 

I very rarely use PVA any more if i can help it WBA all the way for me (thanks Trowel Monkey). I am finding most PVA today is utter crap i am trying out Unibond Original from Toolstation (as you always need to carry a tub in the van and that doesn't seem to bad for minor repairs).
I know WBA is expensive for what it is but i always explain to the costumer what i use and why and nearly all are fine with that. I know it can be a hassle getting it on the day before but worth it in my opinion as you can skim away with confidence all setting time is the same when you use WBA no sections of wall & ceiling going of at different times.
I love WBA cant you tell lol.