plastering over fire/smoke damaged concrete

[johniosaif]

Hi, I am plastering a stairwell in a block of flats which was fire damaged, some of the original plaster ie bonding has blown following the fire, the concrete is now blackened from the heat and smoke.Is it ok to thistle bond it and then hardwall over this blackened area as well as the non blackened concrete..

 

[DannyMac]

I wouldn't use hardwall on smoothish concrete. Use bonding or just skim it if the shuttering is good.

If the black areas are real sooty and dusty, then you need to get most of that off before you use the "bond-it"

 

[malc]

i would dot and dab the wall if poss.
if not the soot must be cleaned off or it will bleed through your plasterwork. you may have to scrabble the concrete to remove the soot.
i would price this work very high as it is time taken

 

[DannyMac]

How about an SBR to seal the soot, followed by a bonding agent?

 

[lilharbs]

Think if it was me I would brush off the soot,then wash off with just water.then maybe sbr seal it then go as per normal.either bonding or dab it.

 

[johniosaif]

I thought the hardwall would be ok with gritted pva? I just want it to last as I get a few fire damaged jobs from a new client and I dont want to appear amateurish. I am happy enough to use bonding..just the main concern been the black bleeding through.I did pva it friday evening and will check tomorrow morning to see how it is ....

 

[lilharbs]

I know it's more on the painters side but,once the plaster is mist coated,a coat of oil based undercoat over it should stop any staining occurring.

 

[Nisus]

Stain block, bonding agent then plaster.

 

[Nisus]

Or wash the lot off first

 

[malc]

plaster will not key to soot. the soot seems to be able to impregnate concrete and brickwork that is why i would try to overboard the area, if not scrabble it out.
float with bonding on concrete not hardwall.