Plaster popout problem with non hydrated quick lime

[Carlo]

Hi. I have recently acquired a villa in Greece and I have a plastering problem I would like to share with this community hoping for some advice on how to deal with it. I have been experiencing many pop outs in the plaster. The result is a crater which must be filled and painted. I typically get around 80 every season. The problem tends to occur more in the winter when there is more humidity. I believe that the quick lime used in the process was not properly hydrated so it tends to expand whilst absorbing humidity causing an expansion of the plaster and hence the pop out. Is there any paint solution I can apply to the walls to eliminate this problem like a one way sealant to allow the walls to expel humidity but not absorb it? Many thanks for your help.

 

[BrummieTrev]

Hi Carlo, is there any pattern to this popping? is it all over the building? at different heights? how far apart do they occur? are all the failures the same in size? does it fail back to the brick/stone background or is it just the top coat? When did the failures first happen? did you PAINT the building when you aquired it or is it lime wash? Possible reasons could be, inadequate re-inforcement in the mix (hair), some kind of timber dowels incorporated in the substrate which expand and contract at a different rate to the brick or stone, masonary paint used instead of lime wash causing trapped moisture to freeze up in the winter and cause the render to blow. Its possible the damage is done in the winter and becomes apparent throughout the year, the material will only drop once all the hair or fibres have rotted causing it to let go. Try and put some answers to the above questions and ill try and narrow it down a bit more.

 

[flynnyman]

Welcome trev where have you been hiding?

 

[BrummieTrev]

Hi mate thank you, I dont get involved much as you can see, this is my first post /reply. lol. Im a lime plasterer, i do modern aswell but my main work is all lime, lath and plaster, fibrous cornice and in-situ work.

 

[lilharbs]

That's gotta be the most in depth and questioning post ever let alone by a newbie.give that man a mug.

 

[Carlo]

Hi Trev,
Thanks for replying. See my answers below:

Hi Carlo, is there any pattern to this popping?

>It seems to be happening in the winter when I don't have any heating on..it's OK in the summer and autumn months

Is it all over the building? yes


at different heights? yes


how far apart do they occur?

variable

are all the failures the same in size? 2mm to 2cm Circular shape


does it fail back to the brick/stone background or is it just the top coat? Top coat I believe


When did the failures first happen? First winter


did you PAINT the building when you aquired it or is it lime wash? standard emulsion paint

I think there are bits of lime in the plaster (not seasoned properly?) and the expand when they absorb humidity in the winter. Would be advisable to paint the wall with water tight paint or is that a bad idea? Any inputs here would be greatly appreciated

Thanks

carl