Plaster crumbling around failed patch on brick wall

[chrissy_a]

I'm doing up a place where there has clearly been some crumbling plaster on brick and it looks like the previous owner has tried to patch it up with a combination of a cut of plasterboard and some of that wall repair gauze, however it's still crumbling and the patch clearly was not up to the task.

The blue side is plasterboard and the other side is plaster on a brick wall. What would be the best way to fix this? My first thought was to try and squirt some expanding foam into the gap to fill it up, and then cut down and smooth over with filler, but looking for some reassurance/suggestions

 

[opps]

As a decorator, I would probably go with expanding foam to begin with.

Don't forget to mist the surfaces with water first. Not only does it aid adhesion, it speeds up curing times.

After dragging out some of the foam, I would apply SBR to the old (visible) plaster.

My filler of choice would probably be a lightweight filler such as Red Devil OneTime. Not cheap but a dream to sand and allows a degree of movement. It does however dry through evaporation, so leave it for a day or two before sanding.

 

[chrissy_a]

Thanks for the advice, much appreciated

 

[chrissy_a]

I would apply SBR to the old (visible) plaster.

Sorry, is this SBR Bond or Admixture?

 

[opps]

Sorry, is this SBR Bond or Admixture?

I would go with regular SBR. Personally, I wouldn't bother to dilute it.

Wipe away any drips though.

 

[chrissy_a]

But what is regular? Searching online most products either seem to be described as an SBR Bond or SBR Admixture

 

[opps]

But what is regular? Searching online most products either seem to be described as an SBR Bond or SBR Admixture

Sorry, I see what you mean.

Sika SikaBond SBR + Waterproof Bonding Agent 5 Litre SIKASBR5 | Sealants and Tools Direct

Most of the SBR that I have purchased in the past can be used for both bonding and as an admixture.

I have only ever purchased it in 5L containers but I have seen 1L bottles online before.

 

[chrissy_a]

Awesome, thank you