Plaster – Corner Bead Cracking?

35har1old

paperclap said:

Hi all,

Two days ago, I'd skimmed some plasterboard (boxing in).

PVA'd the day before, waited for that to dry. Then PVA'd, waited to go tacky, first coat of MultFinish on. After it had started to set, second coat on. Then, three wet trowels.

Corner beads were stapled in place.

Two boxing ins haven't cracked down the corner bead. But this one has. What gives? Could it be as simple as it had dried out too fast due to the PVA not staying on the corner bead (PVA has a tendency to drip down)? Looks like it hasn't bonded properly to the corner bead.

FYI, I'm showing two sections. One where I'd hacked some loose plaster off, another where it's still showing the crack.

Either way, what's the best way to fix? PVA again, and use MultiFinish (2 coats)? Or just fill with EasiFill? Would much prefer to use what I've got (MultiFinish!).

P.S. This is my very first time plastering (ever!), so don't kill me too much for a bad job 

Thanks!

Should have been a fine mesh bead
The bead that you have used has to much of smooth surface

stuart45

I'm not a plasterer by trade, although I've done a fair bit over the years and have never had any problems with the skim beads shown in the photos. Normally only use the mini mesh types when doing an odd angle such as a splayed reveal on a Velux.
I remember a plasterer saying if using PVA, you are better to fix the beads after PVA, as it doesn't adhere to the metal properly. 
Plaster normally sticks to metal, look at a trowel that isn't cleaned up properly.

paperclap

Live update! I'm plastering now as we speak (waiting for the second coat to set)... and my God, it is a horrible job! Not because of the MultiFinish, but because of the awkward angle! Lots of sanding after I reckon 

stuart45

Is it not a 90° angle?

paperclap

It is, but very little room to move a trowel, when going from the corner bead back in to the internal corner... if that makes sense.

Much easier to go from the internal corner to the outer corner (bead)!

FreeBear

paperclap said:

Live update! I'm plastering now as we speak (waiting for the second coat to set)... and my God, it is a horrible job! Not because of the MultiFinish, but because of the awkward angle! Lots of sanding after I reckon 

You shouldn't be sanding Multifinish - It sets very hard.

If you want a "mud" that can be sanded, I'd recommend Knauf Fill & Finish. This stuff can be wet sanded with a sponge float which doesn't produce any dust. And if you dry sand it, it doesn't take much effort. However, I wouldn't use it in a bathroom or kitchen where it can get damp.

paperclap

Ain’t got much choice I’m afraid! It’s already up and dried! 

ThisIsWeird

Give us a pic once done - we need a laff.

Er, I mean, be carefully when you sand it flat so's not to damage the galv.

If it does get scraped, you may find that - after you emulsion it - a small amount of rust stain shows. If so, then just seal it with summat - Zinsser or similar, or an oil-based primer.

paperclap

This might sound a bit crazy… but would an electric sander be too aggressive for sanding plaster? Is there a risk of loosing the plaster?

Would be ideal if I could use one, merely for the dust extraction.

ThisIsWeird

It should be fine. If the plaster loosens, you've got bigger problems