How to repair crumbled away cornice?

[yyecats]

Hi!

I've read through the discussions on how to repair cornices but figured I should check because I didn't feel they quite matched what I am dealing with.

I had a lot of issues with my roof that caused reoccurring water damage and it's now finally resolved, and I'm doing mould treatments but the cornice has crumbled away as you can see from where it was just continuously wet. 

My plan (as someone with zero clue but unplaced confidence and the ability to wing it) was to use spak filler to fill the hole, sand it to make a nice cornice like shape, use an undercoat designed for mould (I even to maybe also use that before I spak fill?) and then going over with some ceiling paint and calling it a day. But now I've read that there is special cornice cement, tape, paper, etc... so just wondering about the best way to go about this. 

[JacobZ · Accepted solution]

Hi @yyecats,

Many thanks for your question and welcome to the Bunnings Workshop community, it is fantastic to have you join us.

Can you advise how soft the cornice is where the water has gotten in? 

It looks in fairly good condition, but if the cornice has lost its strength, I'd advise you to consider removing and replacing it. If you find it is soft in comparison with uncompromised cornice, it would be difficult for the repair material to bond to the cornice and it would likely crack fairly quickly.

If you are happy to go ahead with a repair, I would suggest you start by removing any of the fractured gypsum that you can see on the bottom edge using a utility knife.

Once the fractured material has been removed, you should clean up as much of the mould as you can with a cleaner such as Selleys 750ml Rapid Mould Killer Remover.

Now the loose material has been removed, I'd suggest picking up a Gyprock CSR 1.5kg DIY Rapid Plaster Repair Kit. This handy kit contains all the necessary tools and materials to carry out this repair.

Because of the small size of the repair, it's not 100% necessary for you to use the mesh tape, but it will certainly add some strength if you would like to go a little bit further with your repair.

Mix up the patch repair plaster following the manufacturer's instructions and then apply it to the damaged section using the supplied broad knife. Do your best to form it to the shape of the cornice, but don't stress if it's not perfect, once it has dried, you will need to sand it anyway, so minor alterations can be made.

Once you are happy with the shape, you can apply primer and ceiling paint as you have suggested.

Let me know if you have any further questions.

Jacob

[yyecats]

Thanks @JacobZ 

> Can you advise how soft the cornice is where the water has gotten in? 

All the soft parts have been removed so now it's pretty solid, the parts above the missing chunk don't seem to be soft at all. I see what you mean though, I will remove some more of it to make sure there is no more mould behind. 

Thanks for the response!

[JacobZ]

Hi @yyecats,

It seems counterintuitive, but the fix for most things involving plaster is to make the problem larger before fixing it. Once you're confident the mould problem is dealt with, it should be fairly simple to fix.

Let me know if you have any other questions or run into any issues as your repair progresses, I'm more than happy to assist further.

Jacob