How to prevent cove cornice paper pulling off?

[FCunningham]

Help please!
I am painting over the cove cornice. The original paint is approx 7 years old and it seems an undercoat was never used. I'm using a ceiling white. The new paint has caused bubbles to form between the paper coating and gypsum in the cornice. See attached pic. 

I tried to sand it back and have discovered it is the paper lifting off the cornice, not an adhesion issue between the old paint and the new paint. I didn't notice any issues before it was painted. 

Can anyone tell me what causes this? How do I prevent it from occurring again in other areas of the house? 
Is there any way to fix this section of cornice, other than just replacing the cornice? It runs the length of a room along wall, which is approx 4.5 meters long.

 

[MitchellMc]

Welcome to the Bunnings Workshop community @FCunningham. It's a pleasure to have you join us, and many thanks for your question about painting cornice.

I can't see any reason why painting your cornice would cause a delamination of the paper from the plaster. Perhaps this was already there, and with a fresh coat of paint, it's become more noticeable. I can't say I've come across this issue before, whether that's on a cornice or paper-covered plastered board.  

Given this isn't a commonly occurring issue, there isn't any advice I could provide that would stop it from occurring in the other areas of your home. Perhaps do a test section elsewhere to determine if this one area of the cornice is suffering from this issue. I can't see any alternatives other than replacing the cornice or removing the delaminated paper and filling the areas.
 

It might be worth cutting open one of these delaminated areas to see if there is an underlining issue. It would be odd, but could a roof leak be allowing moisture into this cornice? Water penetration is really the only time I've seen a delamination like this occur.

Please let me know if you have any questions.

Mitchell

[FCunningham]

Hi Mitchell,

Thanks for your reply. 

The cornice does not appear damp and there are no other signs of dampness on the adjacent ceiling or wall (eg no water stains and I would have expected to find that on the ceiling prior to a cornice delamination?). We've inspected the ceiling cavity and it appears OK too. I painted all 4 walls, cornice, and ceiling of this large room (4.5 x 3.4 and 2.4 high) and it has only occurred in one section. maybe I'll put it down to a dodgy piece of cornice originally and proceed with painting other rooms and see how I go. 

I'm about to remove that section of cornice so I guess that will turn up any moisture issues. 

I'll let you know how it goes.

Thanks again,

Fiona

[MitchellMc]

Bit of an unusual one, @FCunningham, and I wish I could give you a definitive answer. I'll be keening awaiting your dissection images of the bubbles as I'd love to see what is inside them/what it looks like.

On a side note, I don't think you've done anything wrong and agree that it could just be a dodgy piece of cornice.

Mitchell

[FCunningham]

If making a mess was the goal, I succeeded. 

I've removed the section of cornice. There was no moisture and no obvious difference between a 'normal' section and the section that was bubbled/delaminating. It all appears dry and is not water stained. My pics show a bubbled section where I had tried to sand it back, but it doesn't demonstrate the 'bubbles' that were underneath the sanded parts. Unfortunately, the camera just wouldn't capture it. I've sent my issue to Gyprock technical services. I'll let you know if they have any insights. 

Thanks for your help.