Many years ago I declined a full facade repointing job in St. Margarets on a large old house. The client demanded weather struck cement pointing like the other houses in the street and I refused. I argued that as the current custodian of this old house she should repair and maintain using the original lime mix. We could take a sample and send it off for analysis and mix recipe. I drove past there a few months later and it had all been done with a strong grey cement based mortar.
I live in an old cottage and since moving have taken a keen interest in lime versus cement discussions. I came across a research paper fron a UK university which essentially concluded that when a weak sand cement mix was tested against limecrete it performed almost identically iin terms of pourosity (breathability), tensile, flexural and compressive strength. So I am in two minds about using lime. Repointing the stonework - definitely lime but for the slab / screed, sand cement mix is just going to be much easier and more convenient. There are two layers of concrete as the existing slab so they are going to be excavated.
Thank you for making this video, and spreading your knowledge to the masses. I own a masonry contracting business in upstate NY, USA. And, i am on a mission to help save the historic masonry structures crumbling and deteriorating due to mass portland cement repairs due to widespread ignorance of the incompatibility of portland and lime over the course of the last century.... I was wondering if I could link to this video on my website and in an upcoming blog post on the subject also for my site. It's quite frankly the most informative, while Still being interesting and explained well and simply enough for anyone to understand regardless their knowledge, or lack thereof, or building or material science. If you want to look at my site first before deciding I will gladly send you the link, i just feel strange about posting it in your comments section, as I am not trying to promote it or spam your channel. It's a great channel and I respect and appreciate your hardwork and willingness to spreading your knowledge! Best regards, Anthony
Hi, please do. It is a major issue over here in the UK, we see far too many properties inappropriately repointed or repaired with OPC. Building owners do not know the difference and sadly many contractors don’t either.
Basic stuff but so important to understand the difference between two fundamental building materials and how they can protect and in equal measure harm a building if used incorrectly.
This is an excellent video, thanks for posting. I moved into a 1930 bungalow and found damp issues in walls, we had the foam cavity wall insulation removed which was soaked and checked air brick ventilation etc. Through the winter the house still smelt and was extremely cold I believe due to wet walls. The house was poorly repointed many years ago with cement so I am considering having it completely repointed, and expecting the original mortar to be lime I tested with vinegar but it does not fizz. The builders who have quoted say cement or a 5-1-1 mix is the normal and has been used forever. After seeing your expert video I wonder what would be your views on this?
@@pthompson044 cavity walls work very differently to solid walls. So long as the mortar mix is weaker than the brickwork you should be good to go. If you have very soft bricks, stick with lime.
An amazing explanation of such an important topic. Thank you for sharing your knowledge. The thing I still don’t understand and it’s been 9 years now of exploring the lime is which lime to use. In your opinion on my Victorian terrace house can I mix up some NHL 3.5 with sharp sand and this will be fine for repointing or should it be NHL 2? Or maybe building sand is best. Some say sharp sand though 😆. Also is NHL (natural hydraulic lime) the correct lime to use for repointing? Is it the case that any lime is fine because of its breathable properties and as long as it’s not cement it will keep those solid walls happy? If you are able to answer this comment that would be amazing. Thank you. Genuinely brilliant video though and I have subscribed. Thanks again
Concrete / Cement Render - a killer of walls in older properties. Not to be confused with Roman Cement Render which was popular in the mid 1800's - very hard but very much a lime based breathable material!
Great vid for me as someone only just starting to learn about this stuff. One question: How can cement mortar be beneficial to say a newer building? Many thanks
Here in the UK I posit that portland cement was not readily available (to buy commercially) in all areas until the 1920s or thereabouts. What would you say to that hypothesis Sir?
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Many years ago I declined a full facade repointing job in St. Margarets on a large old house. The client demanded weather struck cement pointing like the other houses in the street and I refused. I argued that as the current custodian of this old house she should repair and maintain using the original lime mix. We could take a sample and send it off for analysis and mix recipe. I drove past there a few months later and it had all been done with a strong grey cement based mortar.
I live in an old cottage and since moving have taken a keen interest in lime versus cement discussions. I came across a research paper fron a UK university which essentially concluded that when a weak sand cement mix was tested against limecrete it performed almost identically iin terms of pourosity (breathability), tensile, flexural and compressive strength. So I am in two minds about using lime. Repointing the stonework - definitely lime but for the slab / screed, sand cement mix is just going to be much easier and more convenient. There are two layers of concrete as the existing slab so they are going to be excavated.
interesting, too much bickering on forums and not much in the way of quanifiable research it seems.
I expect it was comparing to NHL rather than traditional slaked lime. NHL continues to harden after 30 days.
Thank you for making this video, and spreading your knowledge to the masses. I own a masonry contracting business in upstate NY, USA. And, i am on a mission to help save the historic masonry structures crumbling and deteriorating due to mass portland cement repairs due to widespread ignorance of the incompatibility of portland and lime over the course of the last century.... I was wondering if I could link to this video on my website and in an upcoming blog post on the subject also for my site. It's quite frankly the most informative, while Still being interesting and explained well and simply enough for anyone to understand regardless their knowledge, or lack thereof, or building or material science. If you want to look at my site first before deciding I will gladly send you the link, i just feel strange about posting it in your comments section, as I am not trying to promote it or spam your channel. It's a great channel and I respect and appreciate your hardwork and willingness to spreading your knowledge! Best regards, Anthony
Hi, please do. It is a major issue over here in the UK, we see far too many properties inappropriately repointed or repaired with OPC. Building owners do not know the difference and sadly many contractors don’t either.
Basic stuff but so important to understand the difference between two fundamental building materials and how they can protect and in equal measure harm a building if used incorrectly.
again, thank you for sharing such interesting information.
This is an excellent video, thanks for posting. I moved into a 1930 bungalow and found damp issues in walls, we had the foam cavity wall insulation removed which was soaked and checked air brick ventilation etc. Through the winter the house still smelt and was extremely cold I believe due to wet walls. The house was poorly repointed many years ago with cement so I am considering having it completely repointed, and expecting the original mortar to be lime I tested with vinegar but it does not fizz. The builders who have quoted say cement or a 5-1-1 mix is the normal and has been used forever. After seeing your expert video I wonder what would be your views on this?
@@pthompson044 cavity walls work very differently to solid walls. So long as the mortar mix is weaker than the brickwork you should be good to go. If you have very soft bricks, stick with lime.
An amazing explanation of such an important topic. Thank you for sharing your knowledge. The thing I still don’t understand and it’s been 9 years now of exploring the lime is which lime to use. In your opinion on my Victorian terrace house can I mix up some NHL 3.5 with sharp sand and this will be fine for repointing or should it be NHL 2? Or maybe building sand is best. Some say sharp sand though 😆. Also is NHL (natural hydraulic lime) the correct lime to use for repointing? Is it the case that any lime is fine because of its breathable properties and as long as it’s not cement it will keep those solid walls happy? If you are able to answer this comment that would be amazing. Thank you.
Genuinely brilliant video though and I have subscribed. Thanks again
If the exterior was brick and pointed in lime, would a sand and cement render internally also cause problems in a traditional solid brick wall?
Less of an issue, but still undesirable
What do you think of all the chimney pots that have been repointed using cement motor.
I doubt whether any of the builders use the lime mix.
I doubt so too. It will still be an issue. Thank you for your comment
Concrete / Cement Render - a killer of walls in older properties.
Not to be confused with Roman Cement Render which was popular in the mid 1800's - very hard but very much a lime based breathable material!
That’s the difference between hydraulic lime and non hydraulic lime.
Why don't we just use lime mortar instead of cement to render?
That’s the thing, on solid walled historic houses, we should.
Do you learn all of this on a Bsc Building Surveying?
No not at all unfortunately. Most pathology knowledge is learnt self study post degree.
Great vid for me as someone only just starting to learn about this stuff. One question:
How can cement mortar be beneficial to say a newer building?
Many thanks
Newer buildings are designed differently, so cement is suitable for modern applications.
Here in the UK I posit that portland cement was not readily available (to buy commercially) in all areas until the 1920s or thereabouts. What would you say to that hypothesis Sir?
Yes and therein lies the issue. So many properties built with lime and repaired with cement as it become more commercially available.
What if you put cement on the inside and lime on the outside?
You are still preventing moisture vapour transfer and this can lead to issues.
@@westonesurveyors8139 nuts! 🙃
Yeah just build the whole wall out of hot mix earth mortar and brick in English bond…. Will last 200 years no fuss