How to reattach large piece of plaster cornice?

[Coolaholigah]

I have seen a recent post about reattaching cornice but my repair/problem is bigger.

A 3700mm approx piece of cornice has come down. Luckily it just sagged and I could get it down in one piece it didn’t crash down and break.

Trying to find a match for the cornice has not been possible and, with recently installed wallpaper on other walls in the room under the still good cornice I would prefer not to simply rip it all out and just start again with a new cornice. It is in a granny flat so doesn’t necessarily have to tie in with the rest of the house. 

Anyway, I have tried chipping off the old cornice cement but this damages the cornice. My question essentially is, could I just leave the old cornice cement, put new cornice cement on, and put it back up? I realise the fit would not be as good so the question really is, would the bond be ok? Would sanding off the old cement be a better option? A very labour intensive option but maybe worth a try?

The cornice on the other wall (at left in photo) came down partially too. I have propped that up in the meantime so it doesn’t continue straining on the remaining bond but would new cornice cement be the best option there too?

I realise the joins would not be perfect but as it’s a granny flat I think I could live with that 

[Coolaholigah]

The photo of the cornice cement makes it look as though there is no cement on one surface. There is cement on both surfaces just I was successful in chipping off the cement on the edge at the bottom of the photo in that section. You can see the chipping at the left hand side of the upper edge in the photo

[MitchellMc]

How solidly attached is the cement @Coolaholigah? Since you're having difficulty removing it, it sounds like it's fairly well-adhered. If it's just cracked and the rest is reasonably solid, I'd be leaning toward using construction adhesive and sticking the cornice back into place. As long as the adhesive makes reasonable contact with the wall and cornice, it will do a fine job of holding the cornice in place. You could also use stud adhesive. Once you've applied your glue, you can use screws or nails to hold the cornice in position until the glue sets.

To use cornice cement, you will have to apply enough to bed the cornice into place, and it might end up being proud of the rest. As you said, this might not be so much of an issue, though.

Please let me know if you have any questions.

Mitchell

[Coolaholigah]

Thanks for the suggestions. The construction adhesive link has reviews that are not exactly inspiring. I have used a si,already extreme grab product by Sika and found it difficult to use. But it worked I suppose. Maybe the stud adhesive is a better option in that case.

what about ordinary Liquid Nails? Longer time and horrible colour but maybe easier to use?

would nailing or screwing through the cornice break the cornice though? Obviously it would make a hole to be patched. I’m more concerned about breaking the cornice though

thx for your help

[Coolaholigah]

The viscosity of the Selleys Hold Up (similar to Sika extreme grab I imagine) is what makes it difficult to use. Do you think it would be easier with an electric caulking gun? Would these thick products work with an electric caulking gun. I could hire one perhaps

thx

[MitchellMc]

Hi @Coolaholigah,

You can nail through the cornice, and it's advised to do so in Gyprock's cornice installation instructions. Of course, if you can manage to brace or tape the cornice in position whilst the glue dries, that would also work. If you are concerned about the cornice breaking, I wouldn't suggest screwing through it.

Ordinary liquid nails should be fine to use; it also comes in a clear version. An electric caulking gun would make the use of these products easier. I recently had a large caulking job, so I invested in the Ryobi 18V ONE+ Caulking Gun. It's an amazing tool that's easy to use and will make quick work of the job.

Please let me know if you have further questions.

Mitchell