Preparing old wall for plastering - how much to take off?

[StephenStephen]

Hi all,

We're preparing a wall for lime (putty) plaster, and really struggling to get this layer of black stuff off - how much of it can we get away with leaving on?
Can we just score it?

Bit of history - The wall has been damp for decades (before we moved in), our new neighbours found and fixed the mains leak under their property, the wall is now pretty dry.

The layers are (from the bottom):
-lime plaster (which is quite sound)
-paint
-thin (about a mm or less) layer of black waterproof stuff
-paint

On top of that was a layer of failed render and thin top coat of plaster and paint, which we've removed.

Thanks for your advice, thoughts and suggestions.

 

[KenGMac]

StephenStephen, good evening.

Can I suggest you look @ Soda Blasting"??

 

[StephenStephen]

StephenStephen, good evening.

Can I suggest you look @ Soda Blasting"??

Thanks for the suggestion - unfortunately it wouldn't be appropriate because the plaster is softer than the black stuff.

I'm just wondering if there's been so little response to this because it's lime plaster - so I'm curious what would be the answer to how much needs to come off if it was gypsum plaster we were going to use?

 

[datarebal]

On top of that was a layer of failed render

Ask your self why it failed...
Take off all the black stuff and any paints

 

[StephenStephen]

Ask your self why it failed...
Take off all the black stuff and any paints

Thanks, yes - I guess I was (wishful thinking) hoping it failed mainly because of the (now resolved) damp.

 

[datarebal]

Well the coating probably didn't help keep things alive.
I'd hack it all off, Especialy as your going to the trouble of using lime.
Glad your not using dot and dab rubbish.