- Thread starter cozzie81
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I don't know if it would. If it ain't broke comes to mind
I would be a tiny bit curious that if you removed a bit of render at the base, if the stonework was damp behind it or not, just because I'm nosey.
So I removed a tiny piece of the plaster in one bedroom & placed it in a cup of vinegar, there was a few bubbles & it's definitely making a fizzing sound when I brought it up to my ear.
Could be wishful thinking on my part but it's definitely not as smooth as cement render either, but maybe it was just a poor job.
It looks like it might be brown, at least on the back? Is the top bit of the small lump paint?
If brown I believe it will be most likely gypsum of some kind. Any hairs in it?
Lime plaster fizzes fairly actively and obviously, not just when you hold it up to your ear.
And sometimes cement mixes did have lime added for perceived benefits of flexibility so it isn't quite a black and white test
If brown I believe it will be most likely gypsum of some kind. Any hairs in it?
Lime plaster fizzes fairly actively and obviously, not just when you hold it up to your ear.
And sometimes cement mixes did have lime added for perceived benefits of flexibility so it isn't quite a black and white test
Well I've had another plasterer look at the gable wall as that one is the most exposed to the elements. While no obvious damp is present as suggested on here it doesn't necessarily mean there isn't damp in the stone work.
Unfortunately the kicker is he believes that that there could be significant damage to the stone wall if the thick cement render is removed. He has suggested that maybe leave well enough alone on the external wall & to remove the internal gypsum to at least leave the stone dry out that way.
Any thoughts?
Unfortunately the kicker is he believes that that there could be significant damage to the stone wall if the thick cement render is removed. He has suggested that maybe leave well enough alone on the external wall & to remove the internal gypsum to at least leave the stone dry out that way.
Any thoughts?
Stevers
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If the render has been on there for any length of time, then it's very likely that lime will have been added to the cement mix simply as a plasticiser. If it has always been rendered then the stonework wasn't ever intended to be exposed to the elements and it's weather resistance and appearance are likely to reflect that. If it's been painted then all bets are off as to what was used and what difference that makes.
We've never seen a photo of the outside of this house so it's very hard for us to judge whether it's the sort of stuccoed town house that would always would have been rendered.
I would say it's definitely a cement rendered. It's probably on about 50 yrs or more, was also painted at the bottom section, very unattractive!
I am conscious of the possibility of the damp not actually being visible. So I am going to remove the internal gypsum & see whats going on.
What are people's thoughts on removing internal gypsum to allow any moisture that may be present to dry out.
I was thinking of installing 5mm aerogel with lime plaster internally which is vapour permeable but will help raise the surface temp to reduce the possibility of interstitial condensation. Also add single room MVHR to further reduce stagnant air & to provide ventilation.
I am conscious of the possibility of the damp not actually being visible. So I am going to remove the internal gypsum & see whats going on.
What are people's thoughts on removing internal gypsum to allow any moisture that may be present to dry out.
I was thinking of installing 5mm aerogel with lime plaster internally which is vapour permeable but will help raise the surface temp to reduce the possibility of interstitial condensation. Also add single room MVHR to further reduce stagnant air & to provide ventilation.
Cubist
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Having in recent days seen a suggestion - in a reply to another thread here - that an external cement based render and an internal gypsum plaster could somehow induce the disintegration of the (likely) lime mortar bonding between the bricks/stones of the walls, it may be a very good idea for you to investigate further by removing some of the interior plaster. If the lower reaches of that external wall are found to be almost bone dry and there is evidence of the bonding mortar in effect collapsing to dust or otherwise losing its grip on the surrounding masonry then that would seem to provide some direct evidence in support of the central hypothesis. If on the other hand you find some degree of dampness in those lower reaches of the wall, that would then support the typical understanding of moisture becoming trapped in the fabric of the wall to then rise to perhaps extraordinary heights.
Either way its a good idea to explore further indoors. Given the time of year, deferring exterior work until sunnier weather in Ireland would also be wise.
Either way its a good idea to explore further indoors. Given the time of year, deferring exterior work until sunnier weather in Ireland would also be wise.
Yes I'll keep an eye out for that, thanks Cubist.
IF, as I am extremely hopeful of, there is no obvious damage or dampness internally after I remove the gypsum do you have any opinion on my suggestion of then installing Lime render internally to allow moisture that may penetrate the external cement render to pass through the fabric. While also looking at ways to prevent excess moisture entering the wall internally.
Based on cost and advice & granted it's far from the perfect solution, this seems to be my best option at the moment without doing extensive damage to the external wall but still having a level of breathability & control.
IF, as I am extremely hopeful of, there is no obvious damage or dampness internally after I remove the gypsum do you have any opinion on my suggestion of then installing Lime render internally to allow moisture that may penetrate the external cement render to pass through the fabric. While also looking at ways to prevent excess moisture entering the wall internally.
Based on cost and advice & granted it's far from the perfect solution, this seems to be my best option at the moment without doing extensive damage to the external wall but still having a level of breathability & control.
Stevers
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Not convinced. I was under the impression that the idea that cement renders and gypsum plasters can damage lime mortars was somewhat disputed in that thread. The 'lesson learned' from a very experienced tradesman wasn't all it seemed at face value!
Cubist
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I thought the assertion was quite firmly made in the comment about render and plaster 'sucking the moisture out of the masonry and mortar'. I'm certainly not convinced but if theres any evidence to support the claim I would love to hear it.Not convinced. I was under the impression that the idea that cement renders and gypsum plasters can damage lime mortars was somewhat disputed in that thread. The 'lesson learned' from a very experienced tradesman wasn't all it seemed at face value!
Stevers
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I might have misunderstood, but the sticking point appeared to be sucking the moisture out while somehow keeping it damp!
Cubist
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I understood bone dry and then differential movement effectively grinding the mortar to dust.
LadyArowana
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Prudish? or Poorish? I can see how either might apply, if the house was left naked of its render or the effect that old houses have on the wallet, but neither quite seems to fit the circumstances
Cubist
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I think you have to slur the consonants and bite down on the vowel to get the real feel for the highland terminology.