Breathable Plaster

Hi everyone.
Unique job this one. I don't want to discuss damp proofing or stopping damp as this is not going to happen.
This is a listed public hall that is built into a cliff in the Victorian times.
Lime plaster is not necessary for the listed side of things.
The customer is asking for a breathable plaster as the wall is against the cliff.
This means it will always get damp. the idea is to take back to the mortar and use breathable plaster and paint so it can always dry out from ventilation.
We are not sure if the part I'm talking about is a 1980's add on. The sand render looks like cement based which would lead me to believe that it is 1980's.
The plaster skim is white though with a slight pink tinge.
what would you guys think is the best product bearing in mind I am a time served plasterer but I've never touched lime.

Huge advance Thanks
James

Well I know what @JessThePlasterer would recommend, Limelite render, followed by their skim.

essexandy said:

Well I know what @JessThePlasterer would do to Limelite render, followed by their skim.

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Flotsam&Gypsum said:

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No idea what you are trying to say here, was thinking the shakey face was because you are scared of Jess!.......lol

Limelite system.....sealer, backing & skim

KingCharlesTheTurd said:

Limelite system.....sealer, backing & skim

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Looks like this limelite is the stuff to use then
The customer did not want me to remove the float coat(looks like sand and cement)
So, as they have asked for breathable can I just use the limelite skim over this background?

first of all, lime-lite is a company and they offer a range of products.
Second: they do not seem transparent about their products, I don't know what's in them and in what ratio's.

What you want to achieve with your plaster is improve the convective drying capacity of the wall: the more efficient the wall is at drying itself out, the more successful it will be. More info about this here:



Lime mortar is likely the best way to go. Mix it yourself so that you know what you're applying.

Buying random bags of product rarely guarantee the result that is most appropriate.

currymunster said:

No idea what you are trying to say here, was thinking the shakey face was because you are scared of Jess!.......lol

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Woods said:

first of all, lime-lite is a company and they offer a range of products.
Second: they do not seem transparent about their products, I don't know what's in them and in what ratio's.

What you want to achieve with your plaster is improve the convective drying capacity of the wall: the more efficient the wall is at drying itself out, the more successful it will be. More info about this here:



Lime mortar is likely the best way to go. Mix it yourself so that you know what you're applying.

Buying random bags of product rarely guarantee the result that is most appropriate.

Click to expand...

in an ideal world i'd love to strip it back and start fresh with a better system but my hands are tied by the company that owns the hall. at the moment they have just asked for breathable plaster.
If, as I suspect, it is of 1980's construction then the sand and cement render will have some vapour or DPM behind. there was talk of another part having a fibre one that had failed.
I will email and see what I can persuade.

currymunster said:

in an ideal world i'd love to strip it back and start fresh with a better system but my hands are tied by the company that owns the hall. at the moment they have just asked for breathable plaster.
If, as I suspect, it is of 1980's construction then the sand and cement render will have some vapour or DPM behind. there was talk of another part having a fibre one that had failed.
I will email and see what I can persuade.

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tricky situation... perhaps this case should be approached more like a basement?
look into this: https://www.coreconservation.co.uk/plaster/rinzaffo-mgn/

So this plaster is vapour open but liquid closed. I have not yet worked with this product myself but they have videos illustrating that it indeed stops liquid flow/capillarity. In terms of vapour opennens, I don't know how it performs. But if the pore structure distribution is right, the convective drying capacity should be ideal in theory.

This company claim they got this knowledge passed down to them from old masons working in Venice.

It kind of depends how wet the wall gets... I think a regular lime plaster could work, but if that cliff is really wet and could in some conditions even make the lime plaster "leak" due to the sheer amount of moisture, perhaps a feebly hydraulic lime with volcanic ashes would be better...

The problem is that there is very little scientific research being done in this area so you'll have to wing it a little.

If the wall is not soaking wet, I would go for the regular fat lime plaster (no NHL!!)

if the wall is soaking wet, then maybe a feeble hydraulic lime would be a bit more prudent