Limecrete - Is there any point?

[tvrulesme]

I'm the proud new owner of a Grade II Listed building with a mountain of damp issues. We have a very lengthy remediation plan including exterior masonry paint removal, french drains, re-plastering with lime plaster etc etc.

We have a concrete slab in the kitchen which needs replacing because the levels are all over the place (and it's a recent addition) so my natural instinct was to go down the breathable route and use limecrete. Reading forums it seems to be the Marmite of building materials so I was hoping science would give me a helping hand but reading on Historic England's website they state:

"Proposals often include the replacement of an existing floor with some form of insulated concrete or ‘limecrete’ ground bearing slab. It is a widely-held belief that if an impermeable ground bearing slab is installed in an old building, ground moisture will be ‘driven’ up adjacent walls. Although there are numerous references to this phenomenon, both in technical and product literature, they tend to be anecdotal and unsupported by scientific evidence"

They also point to some research being done by Bath university here:
limecrete-vs-concrete-study

Which concludes "Preliminary results obtained from modelling and laboratory tests suggest that NHL5-based limecrete was marginally more effective than a concrete slab in transferring moisture."

Considering it is not just marginally more expensive, harder to find those with the skills to use it, much longer in drying times and weaker than concrete is there any real point in terms of benefit to the building itself?

I honestly really want to be convinced that it's the way to go but other than people who have had it installed and have dry rooms which could have also been made dry with use of concrete I find no real evidence....

 

[billymultifinish]

The purists will fight for it tooth and nail. There’s no real advantage. And you can strengthen it by adding fibres and/or more lime.

 

[The Hobo]

I'm the proud new owner of a Grade II Listed building with a mountain of damp issues. We have a very lengthy remediation plan including exterior masonry paint removal, french drains, re-plastering with lime plaster etc etc.

We have a concrete slab in the kitchen which needs replacing because the levels are all over the place (and it's a recent addition) so my natural instinct was to go down the breathable route and use limecrete. Reading forums it seems to be the Marmite of building materials so I was hoping science would give me a helping hand but reading on Historic England's website they state:

"Proposals often include the replacement of an existing floor with some form of insulated concrete or ‘limecrete’ ground bearing slab. It is a widely-held belief that if an impermeable ground bearing slab is installed in an old building, ground moisture will be ‘driven’ up adjacent walls. Although there are numerous references to this phenomenon, both in technical and product literature, they tend to be anecdotal and unsupported by scientific evidence"

They also point to some research being done by Bath university here:
limecrete-vs-concrete-study

Which concludes "Preliminary results obtained from modelling and laboratory tests suggest that NHL5-based limecrete was marginally more effective than a concrete slab in transferring moisture."

Considering it is not just marginally more expensive, harder to find those with the skills to use it, much longer in drying times and weaker than concrete is there any real point in terms of benefit to the building itself?

I honestly really want to be convinced that it's the way to go but other than people who have had it installed and have dry rooms which could have also been made dry with use of concrete I find no real evidence....

if u have sand and cement on walls [you are calling concrete ] get rid of it then speak to some old school boy about limework

 

[limeplastering]

I'm the proud new owner of a Grade II Listed building with a mountain of damp issues. We have a very lengthy remediation plan including exterior masonry paint removal, french drains, re-plastering with lime plaster etc etc.

We have a concrete slab in the kitchen which needs replacing because the levels are all over the place (and it's a recent addition) so my natural instinct was to go down the breathable route and use limecrete. Reading forums it seems to be the Marmite of building materials so I was hoping science would give me a helping hand but reading on Historic England's website they state:

"Proposals often include the replacement of an existing floor with some form of insulated concrete or ‘limecrete’ ground bearing slab. It is a widely-held belief that if an impermeable ground bearing slab is installed in an old building, ground moisture will be ‘driven’ up adjacent walls. Although there are numerous references to this phenomenon, both in technical and product literature, they tend to be anecdotal and unsupported by scientific evidence"

They also point to some research being done by Bath university here:
limecrete-vs-concrete-study

Which concludes "Preliminary results obtained from modelling and laboratory tests suggest that NHL5-based limecrete was marginally more effective than a concrete slab in transferring moisture."

Considering it is not just marginally more expensive, harder to find those with the skills to use it, much longer in drying times and weaker than concrete is there any real point in terms of benefit to the building itself?

I honestly really want to be convinced that it's the way to go but other than people who have had it installed and have dry rooms which could have also been made dry with use of concrete I find no real evidence....

Welcome to the forum.
We replace a awful lot of floors in lime. What you will find in almost all circumstances damp will transfer from the concrete slab and up your walls.. I have seen really bad cases of this and am in fact starting one next week so will posts some pictures up.
A floor normally of this age would be tiles laid on earth over time these get damaged and often replaced in a concrete slab.
What you really need to consider is what your looking to have as your finished floor as this will be the huge thing to worry about.
Hope this helps

 

[tvrulesme]

if u have sand and cement on walls [you are calling concrete ] get rid of it then speak to some old school boy about limework

Thank you. Yes I agree with the walls and this makes complete sense to me. The floor, not so much.

 

[tvrulesme]

Welcome to the forum.
We replace a awful lot of floors in lime. What you will find in almost all circumstances damp will transfer from the concrete slab and up your walls.. I have seen really bad cases of this and am in fact starting one next week so will posts some pictures up.
A floor normally of this age would be tiles laid on earth over time these get damaged and often replaced in a concrete slab.
What you really need to consider is what your looking to have as your finished floor as this will be the huge thing to worry about.
Hope this helps

Agreed if a DPM is not correctly installed but if I follow Kingspan plans with DPM folded up the wall to just beyond the floor layer this can't happen can it? In the scenario you mention above replacing with limecrete it seems to me that it is the GEOCELL aggregate below the limecrete which prevents the moisture from getting to the slab in the first place which does the work, not the limecrete itself. Have I misinterpreted this?

In terms of finished floor we are currently looking at either wood or limestone (yorkstone) flags with UFH below in screed. Both breathable, but then not sure if this is relevant if I have a DPM and a vapour barrier as part of the makeup

 

[Tinytom]

Agreed if a DPM is not correctly installed but if I follow Kingspan plans with DPM folded up the wall to just beyond the floor layer this can't happen can it? In the scenario you mention above replacing with limecrete it seems to me that it is the GEOCELL aggregate below the limecrete which prevents the moisture from getting to the slab in the first place which does the work, not the limecrete itself. Have I misinterpreted this?

In terms of finished floor we are currently looking at either wood or limestone (yorkstone) flags with UFH below in screed. Both breathable, but then not sure if this is relevant if I have a DPM and a vapour barrier as part of the makeup

It’s my understanding if you lay a dpm under your concrete floor the moisture that is rising will rise the adjoining walls instead of through the floor slab, so by putting a membrane down you would be making the issue worse, I’m not sure how you would tie this in with ufh though, I’m presuming it would be a good thing as it would help to dry any damp.
Your kingspan plan your referencing will most likely be for a modern house of cavity wall construction.
Is your house solid stone or brick?

 

[tvrulesme]

It’s my understanding if you lay a dpm under your concrete floor the moisture that is rising will rise the adjoining walls instead of through the floor slab, so by putting a membrane down you would be making the issue worse, I’m not sure how you would tie this in with ufh though, I’m presuming it would be a good thing as it would help to dry any damp.
Your kingspan plan your referencing will most likely be for a modern house of cavity wall construction.
Is your house solid stone or brick?

It's brick. I'm not sure I totally buy this, especially if perimeter insulation is used between the slab and the wall of the house which would prevent thermal bridging. There would have to be some pretty significant ground water inside the perimeter of the property to push past the edges of the slab and up into the walls wouldn't there?

Also considering I will be removing exterior masonry paint, repointing with lime, removing internal gypsum plaster, replacing with lime plaster, using breathable paint, creating an external french drain to take away surface water outside and lowering the exterior ground levels surely that would be able sufficient to allow the water from under the floors to evaporate nicely?

 

[limeplastering]

Agreed if a DPM is not correctly installed but if I follow Kingspan plans with DPM folded up the wall to just beyond the floor layer this can't happen can it? In the scenario you mention above replacing with limecrete it seems to me that it is the GEOCELL aggregate below the limecrete which prevents the moisture from getting to the slab in the first place which does the work, not the limecrete itself. Have I misinterpreted this?

In terms of finished floor we are currently looking at either wood or limestone (yorkstone) flags with UFH below in screed. Both breathable, but then not sure if this is relevant if I have a DPM and a vapour barrier as part of the makeup

Hi i think you have misunderstood geocell is basically glass the purpose of this is mainly insulation and bulk. If you use a Dpm the moisture will push from the slab up the walls to around a meter high even if you have lime plaster on the wall it will get damp and you will be forever decorating.
In my personal opinion I would stay well clear from a wood floor it will absorb all moisture and buckle I have seen it loads of times.
You need lime I can’t really understand why you wouldn’t it’s not much more you just need to find the right person for the job.
Where are you based may be some one on here who can help?

 

[Bagrat]

Agreed if a DPM is not correctly installed but if I follow Kingspan plans with DPM folded up the wall to just beyond the floor layer this can't happen can it? In the scenario you mention above replacing with limecrete it seems to me that it is the GEOCELL aggregate below the limecrete which prevents the moisture from getting to the slab in the first place which does the work, not the limecrete itself. Have I misinterpreted this?

In terms of finished floor we are currently looking at either wood or limestone (yorkstone) flags with UFH below in screed. Both breathable, but then not sure if this is relevant if I have a DPM and a vapour barrier as part of the makeup

 

[Bagrat]

Kingspan is a forbidden word when it comes to the lime gurus ! How dare you lol

 

[Tinytom]

It's brick. I'm not sure I totally buy this, especially if perimeter insulation is used between the slab and the wall of the house which would prevent thermal bridging. There would have to be some pretty significant ground water inside the perimeter of the property to push past the edges of the slab and up into the walls wouldn't there?

Also considering I will be removing exterior masonry paint, repointing with lime, removing internal gypsum plaster, replacing with lime plaster, using breathable paint, creating an external french drain to take away surface water outside and lowering the exterior ground levels surely that would be able sufficient to allow the water from under the floors to evaporate nicely?

So if your going to all the hassle of doing the rest of the job properly why not commit to this part too?
I don’t think your fully understanding the way that moisture/water moves through a property, we aren’t saying it’s going to come through your kingsoan concrete visqueen slab, imagine a glass of water filling from the bottom up, you put a credit card in the middle it would come up the sides

 

[tvrulesme]

Hi i think you have misunderstood geocell is basically glass the purpose of this is mainly insulation and bulk. If you use a Dpm the moisture will push from the slab up the walls to around a meter high even if you have lime plaster on the wall it will get damp and you will be forever decorating.
In my personal opinion I would stay well clear from a wood floor it will absorb all moisture and buckle I have seen it loads of times.
You need lime I can’t really understand why you wouldn’t it’s not much more you just need to find the right person for the job.
Where are you based may be some one on here who can help?

Thanks a lot. Yes my lack of understanding is exactly why I posted the question on here. Please don't get me wrong, this is not an attack, just a frustration that the evidence is not readily available. The problem I have is the statement "You need lime". Why? Where is the science that tells me why that would be the right solution? It's not provided by Historic England who state it is "... unsupported by scientific evidence".

I was originally all for Limecrete until reading an old post here pistonheads-forum. I have yet to see anyone explain why limecrete is the way to go. Also you note "you just need to find the right person for the job". If it's such a wonderful option, why not lots more tradespeople trained in it's use and singing it's praises? It's been around long enough and it's not as if we're lacking in historical buildings with damp in this country?

Will definitely stay away from wood floor now though. The existing floor had done just that.

 

[Retired Spread]

I'm the proud new owner of a Grade II Listed building with a mountain of damp issues. We have a very lengthy remediation plan including exterior masonry paint removal, french drains, re-plastering with lime plaster etc etc.

We have a concrete slab in the kitchen which needs replacing because the levels are all over the place (and it's a recent addition) so my natural instinct was to go down the breathable route and use limecrete. Reading forums it seems to be the Marmite of building materials so I was hoping science would give me a helping hand but reading on Historic England's website they state:

"Proposals often include the replacement of an existing floor with some form of insulated concrete or ‘limecrete’ ground bearing slab. It is a widely-held belief that if an impermeable ground bearing slab is installed in an old building, ground moisture will be ‘driven’ up adjacent walls. Although there are numerous references to this phenomenon, both in technical and product literature, they tend to be anecdotal and unsupported by scientific evidence"

They also point to some research being done by Bath university here:
limecrete-vs-concrete-study

Which concludes "Preliminary results obtained from modelling and laboratory tests suggest that NHL5-based limecrete was marginally more effective than a concrete slab in transferring moisture."

Considering it is not just marginally more expensive, harder to find those with the skills to use it, much longer in drying times and weaker than concrete is there any real point in terms of benefit to the building itself?

I honestly really want to be convinced that it's the way to go but other than people who have had it installed and have dry rooms which could have also been made dry with use of concrete I find no real evidence....

@Casper

 

[Casper]

@Casper

You two owe me rent.

 

[Cockney]

You two owe me rent.

Morning Wee Baldy!!
You self taught skimming chancer.

 

[Casper]

Morning Wee Baldy!!
You self taught skimming chancer.

Your missus chucked you oot then? Lol

 

[limeplastering]

Thanks a lot. Yes my lack of understanding is exactly why I posted the question on here. Please don't get me wrong, this is not an attack, just a frustration that the evidence is not readily available. The problem I have is the statement "You need lime". Why? Where is the science that tells me why that would be the right solution? It's not provided by Historic England who state it is "... unsupported by scientific evidence".

I was originally all for Limecrete until reading an old post here pistonheads-forum. I have yet to see anyone explain why limecrete is the way to go. Also you note "you just need to find the right person for the job". If it's such a wonderful option, why not lots more tradespeople trained in it's use and singing it's praises? It's been around long enough and it's not as if we're lacking in historical buildings with damp in this country?

Will definitely stay away from wood floor now though. The existing floor had done just that.

View attachment 67324

Lime allows moisture to pass through it where as sand and cement doesn’t which will trap all the moisture.
The reason you can’t can’t a straight forward answer or explanation is due to the isn’t one! Every single old property is built different the is so many variables water tables cellars ground make up type of soil and so on.
It’s not as easy as you make to learn this I’m 5th generation and as my dad taught me you never stop learning!
Through years of my own job experience working on listed buildings is a tin of
worms one problem will more then likely undercover 3 other ones!
With these houses you can’t cut corners it will come back to haunt you do things properly and keep things simple I think things like ufh and wood floors are not the way to go as it’s not how the building was constructed and not intended to be used .. this is what causes most problems inappropriate materials such as a dpm.
I hope this helps but talking from experience in digging up 100’s of concrete floors and hacking of 1000’s of meters in sand and cement off walls I really hope for your own sake you do it!!

 

[Bagrat]

Lime allows moisture to pass through it where as sand and cement doesn’t which will trap all the moisture.
The reason you can’t can’t a straight forward answer or explanation is due to the isn’t one! Every single old property is built different the is so many variables water tables cellars ground make up type of soil and so on.
It’s not as easy as you make to learn this I’m 5th generation and as my dad taught me you never stop learning!
Through years of my own job experience working on listed buildings is a tin of
worms one problem will more then likely undercover 3 other ones!
With these houses you can’t cut corners it will come back to haunt you do things properly and keep things simple I think things like ufh and wood floors are not the way to go as it’s not how the building was constructed and not intended to be used .. this is what causes most problems inappropriate materials such as a dpm.
I hope this helps but talking from experience in digging up 100’s of concrete floors and hacking of 1000’s of meters in sand and cement off walls I really hope for your own sake you do it!!

Can’t disagree with anything you say but if he is to follow everything by the book it will cost him thousands ?fromm floor flooring to paint . Sometimes we’ll probably nearly all the time it’s always dictated by cost .

 

[limeplastering]

Can’t disagree with anything you say but if he is to follow everything by the book it will cost him thousands ?fromm floor flooring to paint . Sometimes we’ll probably nearly all the time it’s always dictated by cost .

That’s true but listed buildings are not the same as new buildings you can’t just do what you feel like you this is why they are listed.
If your looking to buy a listed property you don’t get a choice you get told what to do and if you chance it without permission you will probably get a fine a customer of mine got a 50k fine a few years back put that in to comparison of doing a 5k floor ( which they would make you re do if you get caught any way! )
Budget doesn’t really come it to play when you hit the listed world if you don’t have the money don’t buy it and if you have a budget double it because you don’t know what your going to find eg some one who has used concrete on the floor!!

 

[tvrulesme]

Lime allows moisture to pass through it where as sand and cement doesn’t which will trap all the moisture.

According to the professors at Bath University who did the scientific study entitled "Comparing the moisture permeability of limecrete and concrete floor slabs" this is incorrect.

I quote "Preliminary results obtained from modelling and laboratory tests suggest that NHL5-based limecrete was marginally more effective than a concrete slab in transferring moisture.""

https://purehost.bath.ac.uk/ws/portalfiles/portal/203983214/Phillips_et_al_2019.pdf

Please note I am specifically referring to the floor slab here. I have no intention of using gypsum or any other cement based product on the walls

 

[Monkey Boy]

If there is only marginal moisture coming up then that can be the difference between damp and dry

 

[limeplastering]

According to the professors at Bath University who did the scientific study entitled "Comparing the moisture permeability of limecrete and concrete floor slabs" this is incorrect.

I quote "Preliminary results obtained from modelling and laboratory tests suggest that NHL5-based limecrete was marginally more effective than a concrete slab in transferring moisture.""

https://purehost.bath.ac.uk/ws/portalfiles/portal/203983214/Phillips_et_al_2019.pdf

Please note I am specifically referring to the floor slab here. I have no intention of using gypsum or any other cement based product on the walls

Unfortunately this is based on a test in a lab.
As I said in my other post every single job is different design make up of build materials earth make up and so on its not as easy as yes or no.
I’ve seen 650 year old property become damp due to a alter in the water table from new build houses on the other side of the road I’ve seen property get damp because the neighbours cut down 2 oak trees.
One thing I do know when I dig up a damp concrete slab and replace it with lime it eventually drys and is no longer damp!
With out being rude I would strongly suggest you forget your ufh and invest the money in a appropriate floor system the is
no point in having warm feet if your plaster looks like s**t and is falling off the wall

 

[tvrulesme]

If there is only marginal moisture coming up then that can be the difference between damp and dry

Hmmmm, pushing the point a little here I think. Look at the table below. Surely we should all be going for bare clay...

What I find worrying is that the limecrete industry seems to be pushing the permeable, breathable nature as unique to limecrete but this is not factually correct. DPM aside, given the study above there seems to be no reason why a concrete slab would not perform equally well at allowing moisture through. So back to the question, is there any real point in Limecrete.

Come on Limecrete, show me the science.....

 

[limeplastering]

Hmmmm, pushing the point a little here I think. Look at the table below. Surely we should all be going for bare clay...

View attachment 67348

What I find worrying is that the limecrete industry seems to be pushing the permeable, breathable nature as unique to limecrete but this is not factually correct. DPM aside, given the study above there seems to be no reason why a concrete slab would not perform equally well at allowing moisture through. So back to the question, is there any real point in Limecrete.

Come on Limecrete, show me the science.....

Here is a bit of science for you in pictures

 

[limeplastering]

Hmmmm, pushing the point a little here I think. Look at the table below. Surely we should all be going for bare clay...

View attachment 67348

What I find worrying is that the limecrete industry seems to be pushing the permeable, breathable nature as unique to limecrete but this is not factually correct. DPM aside, given the study above there seems to be no reason why a concrete slab would not perform equally well at allowing moisture through. So back to the question, is there any real point in Limecrete.

Come on Limecrete, show me the science.....

Correct bare clay is the best way to go only problem not many people really go for that look

 

[tvrulesme]

Here is a bit of science for you in pictures

That's not science. Far too many variables in those pictures to prove that the concrete slab is the key factor to blame. You'd need to remove all the variables. Any number of explanations for that damp

 

[tvrulesme]

Unfortunately this is based on a test in a lab.
As I said in my other post every single job is different design make up of build materials earth make up and so on its not as easy as yes or no.
I’ve seen 650 year old property become damp due to a alter in the water table from new build houses on the other side of the road I’ve seen property get damp because the neighbours cut down 2 oak trees.
One thing I do know when I dig up a damp concrete slab and replace it with lime it eventually drys and is no longer damp!
With out being rude I would strongly suggest you forget your ufh and invest the money in a appropriate floor system the is
no point in having warm feet if your plaster looks like s**t and is falling off the wall

You make a good point here. Nothing quite like experience.

My only counter is that a poorly laid limecrete slab is as useless as a poorly laid concrete slab. Just look at the infamous Grand Designs episode for proof. Given the permeability I suspect that all things being equal if you had replaced those damp slabs with correctly laid concrete the effect would have been the same. Yet clearly going against my own rules as I can't prove with science..,..

 

[limeplastering]

That's not science. Far too many variables in those pictures to prove that the concrete slab is the key factor to blame. You'd need to remove all the variables. Any number of explanations for that damp

Wrong I’m afraid the property has been completed renovated with lime plaster 2 years ago the is no render or paint externally and has been completely repointed in lime the guy knows it’s the floor he was quoted to do it and didn’t you can’t see in the pictures I posted but the gaps in the wood floor are huge.
Your looking for science when really what you should be asking for is case study’s so I will post some up when I find them or go to one later in the week.
You can’t put science on a changeable factor every case is different

 

[limeplastering]

You make a good point here. Nothing quite like experience.

My only counter is that a poorly laid limecrete slab is as useless as a poorly laid concrete slab. Just look at the infamous Grand Designs episode for proof. Given the permeability I suspect that all things being equal if you had replaced those damp slabs with correctly laid concrete the effect would have been the same. Yet clearly going against my own rules as I can't prove with science..,..

That’s true the job is only going to be as good as the person doing it you need to get some one with experience like my self the is way to many people who will just have a go at it

 

[tvrulesme]

That’s true the job is only going to be as good as the person doing it you need to get some one with experience like my self the is way to many people who will just have a go at it

Replying to my own very old post because it took me ages to get to this point. Finally got my Limecrete floor down which was very exciting. Thought I'd share a few pics



These will be finished with Limestone tiles. Just wondering if you use any breathable sealant and if you could recommend one @limeplastering ?

 

[BryanJ]

 

[raytheplasterer]

lime screed NHL 5 with crushed glass insulation ?

 

[tvrulesme]

lime screed NHL 5 with crushed glass insulation ?

Yes I followed this.

 

[raytheplasterer]

seemed the best option, always have admiration for people who invest the time, energy and money into keeping these old buildings alive for the future, too many cowboys around ruining them.