Crumbly wall

by Steve

Hello, I am decorating our office and when taking the wallpaper off we discovered the wall is in really bad condition. A large amount of cracks in the wall along with big chunks of plaster and concrete have fallen off.

I just want to confirm I am doing the right thing here. I am going to coat the wall in PVA 50\50 with some sand mixed in too.

Then once fully dry the next day im going to apply PVA 1\5 to the wall and wait for it to go tacky.

Once tacky, I will apply a coat of bonding plaster to the entire wall, just like plastering.

Then when this coat starts to firm up I will apply finish plaster on top, and then a second coat once the first coat has firmed up.

Does this sound right? Am I using the right thing (bonding coat)?

Thanks guys,

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Apr 28, 2015
Patch up backing coat & skim whole wall
by: Paul

Hi Steve,

Apologies for the delay - guess you've probably had a go already but just in case:

Yes, basically you're along the right lines. The only thing I may do differently is to just apply the Bonding Coat to the deep areas needed as a patch (details here:

If the rest of the wall is fairly rough then you could also apply a thin coat of Bonding Coat plaster but more as a 1st coat of skim plaster, rather than as a backing coat (at the same time apply scrim tape to any cracks). Then as it firms up very important to flatten off any highs (ridges, trowel marks or bumps greater than 2mm need to be flattened) before starting the entire skimming process from stage 1 as normal.

PVA - The initial 50/50 mix may be a bit too strong - it ideally wants to be fairly thin so that it will be absorbed into the porous wall rather than lying on the surface. However if the wall is not at all porous then a 50/50 mix will be fine.

If the wall is porous then a 2nd coat and possibly even a 3rd coat may be needed.


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