Lime Nazis won’t like this!
Discussion
I'm surprised that they're concluding that sand:cement is more breathable than lime*, but in fairness I've been banging on at the lime-huggers for ages on here to try to get them to understand that 'breathability' isn't binary, and that even if lime mortar is more breathable, it still has a pretty high vapour resistivity, when measured against the bandwidth of building materials, overall.
* The figures I've seen previously from tests by organisations such as the BRE suggested cement mortar is about half the figure of lime mortar.
* The figures I've seen previously from tests by organisations such as the BRE suggested cement mortar is about half the figure of lime mortar.
It's not just about the breathability though, is it? It's also the risk of damage to existing lime mortar, stonework and historic, often hand-made, bricks due to inappropriate and indiscriminate use of too much cement. We've had to get rid of cement rendering and pointing over ironstone and bricks in different parts of our house. The cement render slapped on had totally buggered the old bricks, ironstone and mortar.
QuickQuack said:
It's not just about the breathability though, is it? It's also the risk of damage to existing lime mortar, stonework and historic, often hand-made, bricks due to inappropriate and indiscriminate use of too much cement. We've had to get rid of cement rendering and pointing over ironstone and bricks in different parts of our house. The cement render slapped on had totally buggered the old bricks, ironstone and mortar.
This one from the real estate nightmare thread made my teeth itch, to mix threads. OPC mortar pointing is f
king what is presumably limestone.QuickQuack said:
It's not just about the breathability though, is it?
So why pretend that's the reason for using it?We've got clowns on here who would have you believe that you need to use limecrete for ground bearing floors (where no matter how vapour permeable the material is, the only direction water vapour will be travelling is in)
Nobody is saying that there aren't situations where it is appropriate to specify lime products, but as with any material you need to understand how and why to use it, not adopt it as a cure-all snake-oil just because it was the only solution available in the past.
Edited by Equus on Tuesday 30th April 20:42
An interesting experiment, a few thoughts:
The more commonly used sand cement mixes 3:1 & 5:1 fared worse than the NHL 3.5. Which reinforces the widely accepted general view that lime-based mortars are more breathable.
If the sand cement mix was to have a plasticiser admixture added, as is also common, then it is likely to be even less permeable due to lower water cement ratio.
One of the other key benefits to lime mortar beyond breathability is its lower Young’s modulus vs cement mortar I.e its ability to accommodate movement in the masonry. Rigid cement mortars and renders crack letting in moisture, but prevent it from escaping.
It’s important to keep in mind that NHL is a different kettle of fish to hydrated lime - being Naturally Hydraulic (at 3.5NHL grade, moderately hydraulic) the limestone source contains some silica/alumina and so NHL has properties somewhere between Hydrated Lime and Portland Cement. NHL will historically have been used for more exposed locations. Properly old buildings with soft stone will be better served by slaked/hydrated lime, a sample of which would have been interesting to see included in the test as it is what purists would think of when thinking of lime.
The more commonly used sand cement mixes 3:1 & 5:1 fared worse than the NHL 3.5. Which reinforces the widely accepted general view that lime-based mortars are more breathable.
If the sand cement mix was to have a plasticiser admixture added, as is also common, then it is likely to be even less permeable due to lower water cement ratio.
One of the other key benefits to lime mortar beyond breathability is its lower Young’s modulus vs cement mortar I.e its ability to accommodate movement in the masonry. Rigid cement mortars and renders crack letting in moisture, but prevent it from escaping.
It’s important to keep in mind that NHL is a different kettle of fish to hydrated lime - being Naturally Hydraulic (at 3.5NHL grade, moderately hydraulic) the limestone source contains some silica/alumina and so NHL has properties somewhere between Hydrated Lime and Portland Cement. NHL will historically have been used for more exposed locations. Properly old buildings with soft stone will be better served by slaked/hydrated lime, a sample of which would have been interesting to see included in the test as it is what purists would think of when thinking of lime.
T1547 said:
An interesting experiment, a few thoughts:
The more commonly used sand cement mixes 3:1 & 5:1 fared worse than the NHL 3.5. Which reinforces the widely accepted general view that lime-based mortars are more breathable.
If the sand cement mix was to have a plasticiser admixture added, as is also common, then it is likely to be even less permeable due to lower water cement ratio.
One of the other key benefits to lime mortar beyond breathability is its lower Young’s modulus vs cement mortar I.e its ability to accommodate movement in the masonry. Rigid cement mortars and renders crack letting in moisture, but prevent it from escaping.
It’s important to keep in mind that NHL is a different kettle of fish to hydrated lime - being Naturally Hydraulic (at 3.5NHL grade, moderately hydraulic) the limestone source contains some silica/alumina and so NHL has properties somewhere between Hydrated Lime and Portland Cement. NHL will historically have been used for more exposed locations. Properly old buildings with soft stone will be better served by slaked/hydrated lime, a sample of which would have been interesting to see included in the test as it is what purists would think of when thinking of lime.
you'll upset the textbook experts with factual posts like that.The more commonly used sand cement mixes 3:1 & 5:1 fared worse than the NHL 3.5. Which reinforces the widely accepted general view that lime-based mortars are more breathable.
If the sand cement mix was to have a plasticiser admixture added, as is also common, then it is likely to be even less permeable due to lower water cement ratio.
One of the other key benefits to lime mortar beyond breathability is its lower Young’s modulus vs cement mortar I.e its ability to accommodate movement in the masonry. Rigid cement mortars and renders crack letting in moisture, but prevent it from escaping.
It’s important to keep in mind that NHL is a different kettle of fish to hydrated lime - being Naturally Hydraulic (at 3.5NHL grade, moderately hydraulic) the limestone source contains some silica/alumina and so NHL has properties somewhere between Hydrated Lime and Portland Cement. NHL will historically have been used for more exposed locations. Properly old buildings with soft stone will be better served by slaked/hydrated lime, a sample of which would have been interesting to see included in the test as it is what purists would think of when thinking of lime.
Frankychops said:
T1547 said:
An interesting experiment, a few thoughts:
The more commonly used sand cement mixes 3:1 & 5:1 fared worse than the NHL 3.5. Which reinforces the widely accepted general view that lime-based mortars are more breathable.
If the sand cement mix was to have a plasticiser admixture added, as is also common, then it is likely to be even less permeable due to lower water cement ratio.
One of the other key benefits to lime mortar beyond breathability is its lower Young’s modulus vs cement mortar I.e its ability to accommodate movement in the masonry. Rigid cement mortars and renders crack letting in moisture, but prevent it from escaping.
It’s important to keep in mind that NHL is a different kettle of fish to hydrated lime - being Naturally Hydraulic (at 3.5NHL grade, moderately hydraulic) the limestone source contains some silica/alumina and so NHL has properties somewhere between Hydrated Lime and Portland Cement. NHL will historically have been used for more exposed locations. Properly old buildings with soft stone will be better served by slaked/hydrated lime, a sample of which would have been interesting to see included in the test as it is what purists would think of when thinking of lime.
you'll upset the textbook experts with factual posts like that.The more commonly used sand cement mixes 3:1 & 5:1 fared worse than the NHL 3.5. Which reinforces the widely accepted general view that lime-based mortars are more breathable.
If the sand cement mix was to have a plasticiser admixture added, as is also common, then it is likely to be even less permeable due to lower water cement ratio.
One of the other key benefits to lime mortar beyond breathability is its lower Young’s modulus vs cement mortar I.e its ability to accommodate movement in the masonry. Rigid cement mortars and renders crack letting in moisture, but prevent it from escaping.
It’s important to keep in mind that NHL is a different kettle of fish to hydrated lime - being Naturally Hydraulic (at 3.5NHL grade, moderately hydraulic) the limestone source contains some silica/alumina and so NHL has properties somewhere between Hydrated Lime and Portland Cement. NHL will historically have been used for more exposed locations. Properly old buildings with soft stone will be better served by slaked/hydrated lime, a sample of which would have been interesting to see included in the test as it is what purists would think of when thinking of lime.
Equus said:
QuickQuack said:
It's not just about the breathability though, is it?
So why pretend that's the reason for using it?We've got clowns on here who would have you believe that you need to use limecrete for ground bearing floors (where no matter how vapour permeable the material is, the only direction water vapour will be travelling is in)
Nobody is saying that there aren't situations where it is appropriate to specify lime products, but as with any material you need to understand how and why to use it, not adopt it as a cure-all snake-oil just because it was the only solution available in the past.
Edited by Equus on Tuesday 30th April 20:42
The problem is that most people can't grasp more than one basic technical concept in a given field, even if they're working in that field. As a result, they latch onto the simplest explanation they can understand and use that as the reason for all their future advice and decisions. Others who will be able to understand it in the future are only at the beginning of their learning curve and simply don't know enough, but they don't know that they don't know, similar to Dunning-Kruger but about knowledge rather than capability. Some go further and become active snake oil salesmen because they stand to make a profit out of it, but then you get that in every walk of life.I specified it for our house as a result of the damage caused by the cement render and pointing applied over original lime pointing, ironstone and bricks in a 280+ year old house. Restoration using original period techniques and materials seemed the most sensible for our situation. Breathability almost certainly played a part in some of the damage caused to the walls, but it wasn't the only reason; as we both know, it's much more complicated than that in those circumstances. I am not a builder, architect, traditional craftsman or a materials scientist, but I had enough sense to follow the expert advice I was given.
Would you not think that using cement based mixes in historic buildings is risky, especially where people don't fully know or understand the properties of the existing materials and how they may react with cement?
QuickQuack said:
I had enough sense to follow the expert advice I was given.
The problem is that many sources of freely available 'expert' information (particularly on the internet) at best have skin in the game, often as manufacturers/suppliers of lime-based products, or at worst are outright charlatans (PistonHeads naming and shaming precludes me, but if you owned what the Planners might refer to as a heritage asset, in the form of your house, then there are companies out there that might seem a credible source of expert information who I wouldn't trust to believe if they told me water was wet).
Clearly, there are situations where cement-based products are not appropriate (external work on properties that were built using lime mortar), but there are equally instances where use of lime based products is just a slow, expensive waste of money (limecrete floors in most instances) and others still where the use of non-lime based products is neither as harmful nor inappropriate as the 'experts' would have you believe, if handled correctly (eg. insulated dry-lining using composite gypsum plasterboard/PIR), and where the benefits of such products outweigh their disadvantages.
Equus said:
The problem is that many sources of freely available 'expert' information (particularly on the internet) at best have skin in the game, often as manufacturers/suppliers of lime-based products, or at worst are outright charlatans (PistonHeads naming and shaming precludes me, but if you owned what the Planners might refer to as a heritage asset, in the form of your house, then there are companies out there that might seem a credible source of expert information who I wouldn't trust to believe if they told me water was wet).
Clearly, there are situations where cement-based products are not appropriate (external work on properties that were built using lime mortar), but there are equally instances where use of lime based products is just a slow, expensive waste of money (limecrete floors in most instances) and others still where the use of non-lime based products is neither as harmful nor inappropriate as the 'experts' would have you believe, if handled correctly (eg. insulated dry-lining using composite gypsum plasterboard/PIR), and where the benefits of such products outweigh their disadvantages.
so you're saying dry linking and gypsum is better than just a straight forward lime plaster?Clearly, there are situations where cement-based products are not appropriate (external work on properties that were built using lime mortar), but there are equally instances where use of lime based products is just a slow, expensive waste of money (limecrete floors in most instances) and others still where the use of non-lime based products is neither as harmful nor inappropriate as the 'experts' would have you believe, if handled correctly (eg. insulated dry-lining using composite gypsum plasterboard/PIR), and where the benefits of such products outweigh their disadvantages.
Interesting…
Many moons ago (early eighties) I owned and renovated a timber framed house where most panels originally wattle and daub had been replaced by brick.
There was also an extension from 1716. All bricks were either soft reds or tudors.
The pointing was a mess of all ages - most of it in a very hard cement sand mortar and I had to redo the lot.
There was a drastic shortage of lime at the time and I turned to SPAB and the county historic buildings expert for advice and both said use a 10/12:1 sand cement mix with a tiny amount of plasticiser. Still had enough strength but soft enough to allow movement and “breatheability”.
It still looks good today - no more spalled bricks, no effervescence.
The pointing I removed had been weathered struck and I was advised to go sack rubbed. This also makes a difference to the way it performs.
Many moons ago (early eighties) I owned and renovated a timber framed house where most panels originally wattle and daub had been replaced by brick.
There was also an extension from 1716. All bricks were either soft reds or tudors.
The pointing was a mess of all ages - most of it in a very hard cement sand mortar and I had to redo the lot.
There was a drastic shortage of lime at the time and I turned to SPAB and the county historic buildings expert for advice and both said use a 10/12:1 sand cement mix with a tiny amount of plasticiser. Still had enough strength but soft enough to allow movement and “breatheability”.
It still looks good today - no more spalled bricks, no effervescence.
The pointing I removed had been weathered struck and I was advised to go sack rubbed. This also makes a difference to the way it performs.
Equus said:
Frankychops said:
so you're saying dry lining and gypsum is better than just a straight forward lime plaster?
I'm saying that that in some situations it can be, yes, absolutely: it can offer some advantages that traditional lime plastering can't.Frankychops said:
in houses with modern construction and methods.
No, in houses with solid wall construction (which, almost by definition, are not going to be modern construction and methods).Note that I'm saying in some situations.
You seem to be asking or expecting me to say that 'dry lining with gypsum plasterboard is better than lime plaster' (full stop).
That would be just as absurd as saying that lime plaster is always better than dry lining.
Taking such a black-and-white stance is a sure sign of a fanatic, so I'm guessing you're exactly the sort of Lime Nazi that this thread is aimed at. I'm further guessing that because you are sniping at 'textbook experts', you have little grasp of the complexities involved, so are sticking to blind dogma.
Equus said:
No, in houses with solid wall construction (which, almost by definition, are not going to be modern construction and methods).
Note that I'm saying in some situations.
You seem to be asking or expecting me to say that 'dry lining with gypsum plasterboard is better than lime plaster' (full stop).
That would be just as absurd as saying that lime plaster is always better than dry lining.
Taking such a black-and-white stance is a sure sign of a fanatic, so I'm guessing you're exactly the sort of Lime Nazi that this thread is aimed at. I'm further guessing that because you are sniping at 'textbook experts', you have little grasp of the complexities involved, so are sticking to blind dogma.
No, I was just after you expanding on your statement. can you give an example in a historic, solid wall house where it'd be better? Note that I'm saying in some situations.
You seem to be asking or expecting me to say that 'dry lining with gypsum plasterboard is better than lime plaster' (full stop).
That would be just as absurd as saying that lime plaster is always better than dry lining.
Taking such a black-and-white stance is a sure sign of a fanatic, so I'm guessing you're exactly the sort of Lime Nazi that this thread is aimed at. I'm further guessing that because you are sniping at 'textbook experts', you have little grasp of the complexities involved, so are sticking to blind dogma.
I'm a lime fan, not a fanatic. i'm pleased to say I use the correct material where needed, with practical experience. My house has lime and gypsum/cement.
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