Plaster not adhering to plasterboard?

Doozergirl

Do you have the receipt for the plasterboard?  That'll
answer it.  

But yes, the ripple effect.  Plasterboard usually has a plain paper surface.  

It looks like you bought the board and finish on some parallel universe...most odd 🧐

paperclap

It’s reused plasterboard. It was used to board up some polystyrene insulation between the rafters in our loft.

It wasn’t wet, though. But perhaps hot and cold weather over the years has caused it to become rippled? Don’t know.

Doozergirl

Um. In the loft?  

I'm sorry to be dramatic, but are you sure it isn't asbestos millboard?!   That is the sort of place you'd find it! 

https://www.flickr.com/photos/asbestos_pix/4310329031

grumbler

Or some sort of cement board?

paperclap

Got this printed on it! Sure it’s regular plasterboard…

stuart45

The paper on the boards look damaged. The surface is probably coming away a bit as you are laying on. Use new boards.

morhen

Dilute some PVA and coat the plasterboard, once it has dried give it a second coat.  Wait until it is tacky and then put your multi finish plaster on.  If there is any doubt about the quality of the plasterboard, a large sheet is less then £20 so might be worth just buying a new sheet to use.

paperclap

Tell you what I may do.

”Pre-fill” the larger gaps (where the wall meets the plasterboard) with bonding (oh, the irony)… as MultiFinish obviously isn’t suited for any amount of depth. Think they do say it’s a 2mm limit to be fair.

Then try the PVA coat, then MultiFinish.

And if that really doesn’t work then… then, I’ll pop to B&Q, chop up a new sheet of plasterboard I’m half, and squeeze it in my car and start all over again.

Thanks one and all!