How to repair peeling cornice?

[earthperp]

 

Hey all, I've attached a couple images of a cornice that has had its paint peeled away from a bunch of blu tack.

It doesn't seem to be more than a couple mm deep but at some point runs a meter or so.

I was going to sand the area down and use some smooth coat filler in those areas. Once dried, sand and prime it.

Is this the right way to go about it? Or will i need more course filler i.e spackling? Do I need special cornice paint for it?

So many questions! Thanks guys

[JacobZ]

Hi @earthperp,

You'll want to start by tidying up the MDF by removing any loose material and sanding any hard edges. You can use 120-grit sandpaper to do this.

When it has been tidied up, you're going to want to seal the exposed core of the MDF prior to any filling. MDF is extremely absorbent, and if you apply filler straight onto it, the moisture can swell and distort the fibres. For this, I would recommend a shellac-based primer such as Zinsser 369g B-I-N Primer Sealer Stain Blocker Aerosol. This will lock down the surface, prevent swelling, and give you a stable base for repair materials.

Once the primer has dried, the UNi-PRO 500g Smooth Coat Skim Filler will be be a great choice to fill the voids. They are not particularly deep, so there's no need for anything more specialised.

You would then follow the process you have mentioned of allowing it to dry, sanding the filler smooth, then priming and painting. You can use the same Zinsser B-I-N primer over your filler before painting.

Let me know what you think and if you have further questions, please don't hesitate to ask.

Jacob

[earthperp]

Copy that thanks Jacob. I also got some paint peeling in a bunch of spots and was hoping to fill those as well. Is that the same process? I was reading I need anti peel stuff. 

Primer, filler, primer paint? All with appropriate sanding. 

Thanks  

[JacobZ]

Hi @earthperp,

Yes, you could follow the same process, with the one main difference being that you'll want to peel the paint back until you no longer have any lifting paint.

You can use a paint scraper to peel back the paint until you no longer have lifting paint, sand the edges of the patch to remove any hard edges, then prime, coat with filler, prime and then paint.

 Let me know if you have any further questions.

Jacob

[earthperp]

Awesome mate. I spoke to a guy at the painting desk and he said to use this 4 in 1 primer. Is there a reason im using a shellac based one on the cornice but the 4 in 1 is fine for the walls? Or can I just use the 4 in 1 on the cornice as well.

A million questions i know! I appreciate your time.

[JacobZ]

Hi @earthperp,

The basic reason to use shellac-based primer as opposed to a water-based alternative is that shellac-based primers have an alcohol base, which dries extremely quickly (think hand sanitiser) and does not add excess moisture to the surface that can cause the MDF to swell. 

Truthfully, in a small quantity, a water-based primer is unlikely to have adverse effects, but in general, a shellac-based primer is much better for MDF for this reason.

Let me know if you have further questions.

Jacob