Plaster not sealed - painting second coat

greensalad

I am planning to paint the bedroom which has only ever been painted once when the extension was done in 2008. When our decorator (who is also my brother in law) did the hallway ceiling, the whole lot of paint peeled off when he applied the second coat. He explained to me that the plaster hadn't been properly sealed. It went full back to plaster and he had to scrape the whole ceiling and redo a mist coat before he could apply two coats again.

I had painted two other rooms, including the ceiling, upstairs and not had the same issue interestingly. But I just started on some prep work and am concerned that the bedroom has the same issue.

The previous owners stuck vinyl stickers all over the walls. When pulling these off they take the matt paint off and reveal what looks to me like raw plaster. 



It has no colour like a white wash, nor does it have any shinyness I'd associate with PVA. So I'm thinking it wasn't done properly. The whole extension has problems and appears to be a bit of a cowboy/cheap job so I'm not surprised. But the other walls upstairs have been fine, with the exception of the ceiling on the landing. 

I've scrapped the peeling paint off just in this area, just the stuff that was willing to come off with a filling knife, didn't go hard at it. 

I was considering putting on a very thin layer of plastering compound I have to fill in the area, then sand it down smooth.

Then I was considering applying a mist coat to the entire bedroom before I get started. My hope is this would give me enough grab for my new matt vinyl paint. My question is does a mist coat really work over the top of existing paint (two coats, I presume), to seal in plaster? Or does it only do something on raw plaster. 

I obviously desperately want to avoid having to scrape the entire room back to plaster.

rob7475

A mist coat over the top won't seal it I'm afraid. If you go at it with sanding sheets on a pole, the old paint might come off easily if it wasn't applied properly. You've then got a nice surface to start from again.

Alternatively, lining paper ove the log before repainting.

greensalad

rob7475 said:

A mist coat over the top won't seal it I'm afraid. If you go at it with sanding sheets on a pole, the old paint might come off easily if it wasn't applied properly. You've then got a nice surface to start from again.

Alternatively, lining paper ove the log before repainting.

Nooo I was hoping you weren't going to say that. 

Lining paper could work but we were planning to paint the ceiling too which would be a nightmare to paper!

rob7475

greensalad said:

rob7475 said:

A mist coat over the top won't seal it I'm afraid. If you go at it with sanding sheets on a pole, the old paint might come off easily if it wasn't applied properly. You've then got a nice surface to start from again.

Alternatively, lining paper ove the log before repainting.

Nooo I was hoping you weren't going to say that. 

Lining paper could work but we were planning to paint the ceiling too which would be a nightmare to paper!

Zinsser do a product called peel stop. I've never used it and not sure if it would be suitable for a plastered wall or not. It may be worth contacting Zinsser support to see if they can recommend a product for you

liberty_lily

Not saying it's necessarily an option for you @greensalad, but we have a similar shoddily built (by a previous owner) extension where the walls were very obviously not mist coated prior to painting. When we first purchased the house in 2018 I scraped back as much of the offending, peeling paint as possible and filled then repainted (with blooming expensive Little Greene emulsion 🙄) only to have it start peeling in other areas. Some parts of the finish plaster has come away too 😡

Now we're tackling the space properly - ie, we've removed the badly built, single-glazed frontage and replaced with oak framed, full height, double-glazed panels - we've decided the best option is to batten the walls, plasterboard and replaster the lot. We'll be taking the opportunity to add some extra insulation at the same time. 

Time consuming and fairly expensive (although we're doing all the work ourselves) but worth it imho!

greensalad

liberty_lily said:

Not saying it's necessarily an option for you @greensalad, but we have a similar shoddily built (by a previous owner) extension where the walls were very obviously not mist coated prior to painting. When we first purchased the house in 2018 I scraped back as much of the offending, peeling paint as possible and filled then repainted (with blooming expensive Little Greene emulsion 🙄) only to have it start peeling in other areas. Some parts of the finish plaster has come away too 😡

Now we're tackling the space properly - ie, we've removed the badly built, single-glazed frontage and replaced with oak framed, full height, double-glazed panels - we've decided the best option is to batten the walls, plasterboard and replaster the lot. We'll be taking the opportunity to add some extra insulation at the same time. 

Time consuming and fairly expensive (although we're doing all the work ourselves) but worth it imho!

That's interesting! I definitely feel like I need to add more insulation. It's not so bad in the bedrooms somehowe but the bathrooms are always so cold!

Unfortuantely I feel like reboarding the whole place is not a job I could do easily, due to the shape of the room. If it were a rectangle I'd consider it but it's a loft conversion and therefore has eaves... it's a totally odd shape of room!

I've got carpets booked on the 7th so have limited time, still got to paint, put in new skirtings and wallpaper the whole space!