Plaster distemper!

[HS207]

Hello there, I am renovating a Victorian hall/stairway and have had the underside of the upper stairs run skimmed to match the underside of the landing. Unfortunately a 1.5 metre stretch has developed damp/distemper blotches where I did not remove the original off white smooth lath and plaster due to it appearing sound and smooth. Had I known the result I would have bit the bullet and gone for the full removal! I am now unsure whether to try to seal the plaster or have the disruption of removing it and risking an uneven joint with the landing etc.
Could anyone please recommend a resilient sealer which can offer a long term solution to this problem? Any assistance will be appreciated.

 

[Moo]

A picture* would help, as well as a bit more detail about what you were actually skimming over.
I'm no expert, but I suspect that applying gypsum to a lime (plaster/lime wash) substrate might cause the sort of problem that you've described.

* when I say 'picture' I mean, of course, Lots of Pictures. Outside, inside.... the more the merrier! PPUKers are terribly nosy!

 

[HS207]

Hi there Moo, I have tried to upload a few pictures as you have suggested, but unfortunately I have been unsuccessful in uploading them as yet. In light of this are you or any other members aware of any practical solutions to the gypsum/lime reaction that you have described? This seems to be the most likely cause of the problem. I hope to have the hall ready for decorating done in the next month and white emulsion paint would not last long on the distemper!

 

[JoceAndChris]

I would telephone Rose of Jericho. They may well suggest Claircolle. A layer of this prior to using fresh distemper worked well in our dining room.

http://www.rose-of-jericho.demon.co.uk/safety/rj5_04a.htm

Are you sure no damp is seeping in somehow?

 

[skier-hughes]

Am I right in thinking you have gypsum plaster skimmed over a lime plaster base?

 

[HS207]

Hi there Joce and Chris, I am quite sure that there is no damp involved in this case. The blotches are on the underside of a stair case and only occurred after it had been skimmed with gypsum. As I have said if I had known I would have taken all the lath and plaster down despite the dust! Or alternatively it would have been worth a sealer before the skim was applied. Thank you for the link, I will try them tomorrow.

 

[HS207]

Hello skier-hughes, yes that is the case I am afraid!

 

[JoceAndChris]

Oh dear, not great putting gypsum over lime, not a happy marriage. Best of luck with sorting it out.

Also, well done for not actually pulling down the lath and plaster ceiling. A lot of us on here are very attached to the old fabric of the building that tells the history of the house - and once it's gone it's gone. I have pulled down lath and plaster ceilings in a previous home and regret it now, nobody else is going to get to see that and have that feeling of going back in time.

Lots can be done with old ceilings, we spent a few months on one of ours here, picking off all the finishes, restoring the lime work, having new lime patched in, and then distempering. It looks great.

Not meaning to be harsh on you as I haven't got the full picture but a lime repair would have been better.