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christianb
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Hi Michael,
The terminology relates to the relative abilities of the limes to set under water.
NHL2 = feebly
NHL3.5 = moderately
NHL5 = eminently
The actual numbering, on the other hand, relates to compressive strength. As such, 2 tends to used mostly for plastering work, 3.5 for general pointing, and 5 for more extreme external uses. Indeed, it is the latter that the underwater foundations of Tower Bridge are built upon (it sets under water and is as hard as modern concrete). How hydraulic a lime is depends upon its relative purity (5 having a higher mineral content and thus the least "pure").
It should be pointed out, though, that lime putty (which can be created from hydrated lime) is preferable for interior plastering - or at least combined with some NHL2.
Hope this helps.
The terminology relates to the relative abilities of the limes to set under water.
NHL2 = feebly
NHL3.5 = moderately
NHL5 = eminently
The actual numbering, on the other hand, relates to compressive strength. As such, 2 tends to used mostly for plastering work, 3.5 for general pointing, and 5 for more extreme external uses. Indeed, it is the latter that the underwater foundations of Tower Bridge are built upon (it sets under water and is as hard as modern concrete). How hydraulic a lime is depends upon its relative purity (5 having a higher mineral content and thus the least "pure").
It should be pointed out, though, that lime putty (which can be created from hydrated lime) is preferable for interior plastering - or at least combined with some NHL2.
Hope this helps.
Penners
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Shows how wrong you can be.
I thought your thread was about an Anthony Minghella film.
I thought your thread was about an Anthony Minghella film.
Feltwell
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Penners said:
Which one, Atonement?
I wondered if it was a sequel to Truly, Madly, Deeply - so we were thinking along similar lines. A lovely film.
Penners
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Yes, if you like mawkish, weepie, chick-flicks. :xFeltwell said:
Feltwell
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Bah Humbug!
Many thanks for your responses. I must admit that having looked at this website for perhaps a couple of years now; I still get very confused when it comes to hydrated and hydraulic lime and in which situations to use them.
Now that spring has sprung, I need to address a bit of re-pointing on my house and whilst looking through this website for some inspiration I came across a couple of links which I think were written in collaboration with The Old House Store.
The first link gives a nice clear guide on how to re-point a wall
http://www.periodpropertyshop.co.uk/acatalog/Repointing.html
And at the bottom of that page, there is a second link which advises you on which lime mortar to use.
http://www.periodpropertyshop.co.uk/acatalog/LimeGuide.pdf
It’s that second link which uses the terminology Feebly, Moderately and Eminently as well as Coarse stuff.
As Christianb has explained, these are all grades of hydraulic lime (NHL- Natural Hydrualic Lime) with the above terminologies referring to their ability to set under water and the numbering referring to their compressive strength.
My problem is that I’m sure over the past couple of years that various posts on this site have advised me to use Hydrated lime or a lime putty and well graded sand mix for my re-pointing. Dose this mean that the PPUK/OHS links are expressing a different school of thought or am I just not getting it? As Chritianb also points out, NHL 3.5 tends to be used for general pointing.
If that’s not confusing enough, The second PPUK/OHS link also looks at the hardness of your brick and the exposure of the property when selecting your mortar. OK I’m not right on the sea edge but I am in a coastal town in a fairly high elevation so I guess I’m fairly exposed. The property is early 19th Century, solid 9” brick walls and whilst I would describe the internal face of the wall as soft brick, the outer fair face brickwork seems relatively hard to me with very little deterioration.
Help please!
Now that spring has sprung, I need to address a bit of re-pointing on my house and whilst looking through this website for some inspiration I came across a couple of links which I think were written in collaboration with The Old House Store.
The first link gives a nice clear guide on how to re-point a wall
http://www.periodpropertyshop.co.uk/acatalog/Repointing.html
And at the bottom of that page, there is a second link which advises you on which lime mortar to use.
http://www.periodpropertyshop.co.uk/acatalog/LimeGuide.pdf
It’s that second link which uses the terminology Feebly, Moderately and Eminently as well as Coarse stuff.
As Christianb has explained, these are all grades of hydraulic lime (NHL- Natural Hydrualic Lime) with the above terminologies referring to their ability to set under water and the numbering referring to their compressive strength.
My problem is that I’m sure over the past couple of years that various posts on this site have advised me to use Hydrated lime or a lime putty and well graded sand mix for my re-pointing. Dose this mean that the PPUK/OHS links are expressing a different school of thought or am I just not getting it? As Chritianb also points out, NHL 3.5 tends to be used for general pointing.
If that’s not confusing enough, The second PPUK/OHS link also looks at the hardness of your brick and the exposure of the property when selecting your mortar. OK I’m not right on the sea edge but I am in a coastal town in a fairly high elevation so I guess I’m fairly exposed. The property is early 19th Century, solid 9” brick walls and whilst I would describe the internal face of the wall as soft brick, the outer fair face brickwork seems relatively hard to me with very little deterioration.
Help please!
christianb
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Hi Michael,
Lime putty mortars are the starting choice. If your property is unexposed and constructed of "soft" stone, there's no reason to use anything else. The next logical choice, of course, is NHL2, but it really isn't that much different to putty except in its being slightly less workable (putty is a joy to use in comparison) and a mite tougher. For a building which takes a fair bit of weathering, go with NHL3.5. Grade-5, on the other hand, is totally unnecessary in this case and will set like metaphorical concrete and be much harder than your brickwork in a couple of years.
The thing to remember is that the mortar really should be sacrificial to the stone. But at the same time you don't want it to erode rapidly. You could use some 3.5 mixed with a bit of putty for workability.
Others may have a different view, but for exterior work that's what I'd go for. And either way, you'd still be avoiding rock-hard OPC!
C.
Lime putty mortars are the starting choice. If your property is unexposed and constructed of "soft" stone, there's no reason to use anything else. The next logical choice, of course, is NHL2, but it really isn't that much different to putty except in its being slightly less workable (putty is a joy to use in comparison) and a mite tougher. For a building which takes a fair bit of weathering, go with NHL3.5. Grade-5, on the other hand, is totally unnecessary in this case and will set like metaphorical concrete and be much harder than your brickwork in a couple of years.
The thing to remember is that the mortar really should be sacrificial to the stone. But at the same time you don't want it to erode rapidly. You could use some 3.5 mixed with a bit of putty for workability.
Others may have a different view, but for exterior work that's what I'd go for. And either way, you'd still be avoiding rock-hard OPC!
C.
christianb
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michael said:
Sounds pretty dandy to me!
Excellent. I can now get on with the job. Thank you.
One last question. Would it be ok to have a different mix for re-pointing the inside face of the building where there is no exposure and the bricks are much softer i.e. 1 lime putty to 3 sand for the inside and the mix stated above for the outside?
One last question. Would it be ok to have a different mix for re-pointing the inside face of the building where there is no exposure and the bricks are much softer i.e. 1 lime putty to 3 sand for the inside and the mix stated above for the outside?
When you mix, make sure that you bash the hell out of the mixture. It makes it a lot easier to use.
I mix in an ordinary cement mixer but don't find this does a good enough job by itself. Before use, I fill half a tub and use a paddle mixer (<£10) + geared SDS drill (<£40) to really give it a good going over. This makes the mixture a lot sticker and easier to spread.
I find that mixing dry first and then adding water gives the best result though as you are using putty you may have to experiment a bit with this. Be careful not to put too much water into the mix. It takes a lot lot longer than cement to come to its final consistency so mix, mix and mix again before adding additional water. I would suggest starting with a 3/4 load in the cement mixer on your first attempt so that you can add more lime / sand when you put too much water in...
I would very much use just lime putty + sand for inside. It is the better thing to use (I believe) and will keep in a tub forever if you want to mix a large batch. The NHL mixture wont.
I mix in an ordinary cement mixer but don't find this does a good enough job by itself. Before use, I fill half a tub and use a paddle mixer (<£10) + geared SDS drill (<£40) to really give it a good going over. This makes the mixture a lot sticker and easier to spread.
I find that mixing dry first and then adding water gives the best result though as you are using putty you may have to experiment a bit with this. Be careful not to put too much water into the mix. It takes a lot lot longer than cement to come to its final consistency so mix, mix and mix again before adding additional water. I would suggest starting with a 3/4 load in the cement mixer on your first attempt so that you can add more lime / sand when you put too much water in...
I would very much use just lime putty + sand for inside. It is the better thing to use (I believe) and will keep in a tub forever if you want to mix a large batch. The NHL mixture wont.