Yesterday I filled in the chases that had cables in plastic oval that I made in the wall. I used multi-finish plaster. In general it went OK, but in some of them I have some small cracks that appeared after it started to dry? I have more cracks where I tried to fill in plaster that had come loose near the ceiling.

My process was to paint in 1:5 PVA:water a few days ago and let dry. Then before plastering I painted in 1:3 PVA:water and let it go tacky before filling the channels and repairing plaster.

I'm not really sure what went wrong. Did I use the wrong product? Any ideas? Do I just need to put another thin coat on top to smooth/fill the cracks? Thanks!

You used multi to fill in the chases?

Multi is for finishing only. If the chase was anything more that a few mm deep then you should have used either bonding or hardwall to build it up first, depending on whats behind the surface. Then you could go over with multi to finish.

Thanks, I've been reading and I think that it was the wrong product (like you said) and dried too quickly.

Rookie move, I'll just either pull it out if it doesn't harden properly and try again or try to finish it off with poli-fill and sand (there is nothing in the room so dust doesn't matter).

Would it be better to take it out and do it again with bonding/hardwall and then multi-finish or level it up with easi-fill and sand?

Depends how blown the multi is, but probably yes.

Forget the easyfill and sand bit.

If behind the plaster is brick then use hardwall, if the background is anything else use bonding but do apply pva first (for bonding). Leave at least a mm or two under the surface of the adjoining plaster, key it or if still damp bring up to the surface with multi and smooth off and feather to adjoining.

Just a thought. Are you planning to re-skim the whole wall? If so you could leave it all as you've done and just apply scrim tape over the crack, just so long as the rest is holding, and then just re-skim the whole of the wall.

Behind the wall is brick, as the surface plaster is only about 2-3mm. The chases go down about 3cm into the brick. In this case I should try again with hardwall with a surface of multi-finish.

Well, that's one way to learn. Thanks for the advice.

if this was me i would drag out the multi and re-do using hardwall even if you intend to skim the whole wall.

as previously mentioned give the brick a good drink or use a pva mix if you like and bring out with hardwall until a few milli's shy, then use your multi to bring out level and feather in.

good luck

if this was me i would drag out the multi and re-do using hardwall even if you intend to skim the whole wall.

as previously mentioned give the brick a good drink or use a pva mix if you like and bring out with hardwall until a few milli's shy, then use your multi to bring out level and feather in.

good luck