Need to fill plaster back to the brick on chimney breast

[Rick Sanchez]

Part of my bathroom is fitted around an old fireplace. I am re-tiling, after pulling the tile off of this one section he plaster is knackered.

Is about 70cm high an 20cm wide, it crumbles away when you touch it. I just need a surface I can tie to, but its too big and deep for Polyfilla. Can anyone recommend the best way forward? I might just batten and plasterboard it!

 

[KenGMac]

Rick Sanchez, good evening.

As you have posted, the Plaster is shall we call it "Shot" Any attempted use of Polyfilla or similar is totally futile

Suggest you consider removing all this defective Plaster, replace with Foil backed Plasterboard on timber stud.

Why Foil backed board? to make sure no moisture from the bathroom gets into what will become a gap when you fit the stud and plasterboard, why? because the area you are about to block of was a fireplace, this in turn indicates that the masonry will be impregnated with Sulphate [a By-Product of the combustion of coal and wood]

Foil back board will halt the transference of air borne moisture vapour into the void, that will be formed when you fit the Plasterboard.

Sulphate will attack mortar, and plaster, if you form a gap between the masonry and the new Plasterboard this will eliminate Sulphate attack.

Ken.