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Anonymous
Guest
Yes, NHL.5 is a very strong set, far too strong to use with worn and friable stone or brickwork. Use the NHL3.5 instead for your chimney.
Sue
Sue
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A
Anonymous
Guest
Ah, that's a description problem then, by well graded I mean a good mix of a lot of varying size pieces of sharp aggregate. It should all be sharp, nothing smooth in there because the lime can't bind to the smooth pieces, whereas sharp angles are excellent to adhere too.
Some of the pieces can be 2-3mm even, provided there are lots of progressively smaller pieces in with it. This gives a good looking mortar and also a good base for the binder to firm up on.
Sue
Some of the pieces can be 2-3mm even, provided there are lots of progressively smaller pieces in with it. This gives a good looking mortar and also a good base for the binder to firm up on.
Sue
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Anonymous
Guest
Earlier in the summer, when I was still optimistic about how much I would get done this year, I bought a bag of hydrated lime, tipped it into a bin and mixed it with water. I've stirred it with a garden fork every so often and it looks like a a good thick pancake mix. Since we have already had a couple of decent frosts (had to scrape the car windscreen this morning!) I guess it is time to move the bin into the garage. From my description does the putty sound OK? I've probably got too much water in the bin, so can I pour off most of what is above the settled putty? Since we are promised a return to more average winter temperatures for this year, how sensitive is the putty to freezing?
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Anonymous
Guest
I think it might be best to leave it in the bin without stirring it. You won't have done any harm but now leave it alone to settle. It will settle into a putty that gets stiffer and less watery with age. All the spare water will remain at the top and become quite clear. When you come to use it you can just tip the tub up and pour it off. Keep this limewater to return to the tub to cover what you don't need. You can't have too much water in the tub. When mixing with the aggregate you will need little or no extra water.
About this time last year Evelyn was issueing weather warnings and I raised the question of weather frost could damage putty in a tub. I said I couldn't think of a physical reason why it should and said I'd leave a tub out to find out. We had a mild winter and it never froze. So much for the empirical approach. I'll try again this year.
Yes, Sue, you're right. I don't think I described 'well graded' very well. It's a term which really only makes much sense if combined with the sieve figures though.
About this time last year Evelyn was issueing weather warnings and I raised the question of weather frost could damage putty in a tub. I said I couldn't think of a physical reason why it should and said I'd leave a tub out to find out. We had a mild winter and it never froze. So much for the empirical approach. I'll try again this year.
Yes, Sue, you're right. I don't think I described 'well graded' very well. It's a term which really only makes much sense if combined with the sieve figures though.
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Anonymous
Guest
Great find, Sue. I've added it to my Favourites for future reference.
I've not seen that particular article before, but I've certainly read about the problems with using cement to guage lime mortars.
I've not seen that particular article before, but I've certainly read about the problems with using cement to guage lime mortars.
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Anonymous
Guest
Thanks for that. Your chimney restoration was most impressive.
It sounds as though NHL3.5 is just the job for both soft brick and soft sandstone chimney stacks.
From what I've read, the moderately hydraulic lime mortars would need 3 to 4 weeks to cure sufficiently to resist frost.
If I do the work now I will be taking a risk with the weather. I am tempted to defer it until spring.
We're at a similar lattitude - how late in the year was it when you repaired your stacks? Just out of curiosity.
Ian
It sounds as though NHL3.5 is just the job for both soft brick and soft sandstone chimney stacks.
From what I've read, the moderately hydraulic lime mortars would need 3 to 4 weeks to cure sufficiently to resist frost.
If I do the work now I will be taking a risk with the weather. I am tempted to defer it until spring.
We're at a similar lattitude - how late in the year was it when you repaired your stacks? Just out of curiosity.
Ian
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Anonymous
Guest
I've checked the date stamp on the photographs and they show that the two rebuilt chimneys were done 1-3 October, and the other 4 chimneys were re-pointed after that up to the 12th Cotober. We did use hessian to cover everything, and we put some boards around the scaffolding to keep the wind off. I think we left it all covered for a good week before we dismantled that part of the rig.
The haunching/flaunching was done in a weak 1x2x9 mix of white cement, lime and sand. It's fairly easy to chip off, which it will be when the s/s liner needs replacing in a decade or so perhaps. Most of it is in contact with the steel plate, not the brickwork.
The haunching/flaunching was done in a weak 1x2x9 mix of white cement, lime and sand. It's fairly easy to chip off, which it will be when the s/s liner needs replacing in a decade or so perhaps. Most of it is in contact with the steel plate, not the brickwork.
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Anonymous
Guest
Thanks for all the replies. It is a case of do a fix now and do it again next year in the larger job.
I'm still not sure what to go with. I think I found a supplier of NHL fairly locally so I might get a bag of 3.5 and do it with that. Interestingly, I've had a load of conversations with lime company people and the local conservation. They all recommend that any re-pointing work is done 1 part NHL 3.5 : 3 parts sharp sand. The house is mainly engineering brick with some sandstone. We do have an issue with the chimney stack as well (brick) and in all conversations with the above people I have been told to use NHL 5 as the area is so exposed.
This seems to contradict what some of you are saying here. Also, the lime companies I spoke to didn't advocate the use of putty quite as keenly as some of you do, even though they were makers/supplies.
Still a bit confused, but getting there!
I'm still not sure what to go with. I think I found a supplier of NHL fairly locally so I might get a bag of 3.5 and do it with that. Interestingly, I've had a load of conversations with lime company people and the local conservation. They all recommend that any re-pointing work is done 1 part NHL 3.5 : 3 parts sharp sand. The house is mainly engineering brick with some sandstone. We do have an issue with the chimney stack as well (brick) and in all conversations with the above people I have been told to use NHL 5 as the area is so exposed.
This seems to contradict what some of you are saying here. Also, the lime companies I spoke to didn't advocate the use of putty quite as keenly as some of you do, even though they were makers/supplies.
Still a bit confused, but getting there!
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Anonymous
Guest
Thanks again, #51 for that useful information. It's all very well me reading the text books, but it is a great deal better to be able to benefit from your first hand experience, and successful results.
You protected your work very well by all accounts. I will make sure that I do the same, whenever I do my chimney. It also looks like you just got the work done in time, and were also very lucky with the mild weather last year.
The worst scenario for fresh mortar (and this goes for c****t too) appears to be heavy rain that saturates everything followed by a sharp frost. I'd imagine that the water freezing in the mortar would pretty much destroy it, leading to an unstable structure.
Perhaps some sort of temporary roof could be rigged over the stack to keep the rain off, in additition to hessian etc?
Then again, the NHL needs water present in order to cure, so you've got the risk of frost damage anyway once we're deep into Autumn.
I think I'll heed Evelyn's words of caution and leave it 'til spring now.
You protected your work very well by all accounts. I will make sure that I do the same, whenever I do my chimney. It also looks like you just got the work done in time, and were also very lucky with the mild weather last year.
The worst scenario for fresh mortar (and this goes for c****t too) appears to be heavy rain that saturates everything followed by a sharp frost. I'd imagine that the water freezing in the mortar would pretty much destroy it, leading to an unstable structure.
Perhaps some sort of temporary roof could be rigged over the stack to keep the rain off, in additition to hessian etc?
Then again, the NHL needs water present in order to cure, so you've got the risk of frost damage anyway once we're deep into Autumn.
I think I'll heed Evelyn's words of caution and leave it 'til spring now.
A
Anonymous
Guest
Since tha article, (1999) the Smeaton Project results have been published.
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Anonymous
Guest
the current vogue for using hydraulic lime has arisen largely to creative marketing; it has been stated that all historic mortars were hydraulic.... this is largely due, in my opinion, to the contaminates within aggregate (read 'pozzalanic material') rather than the nature of the limestone. 'inclusions' within the aggregate will produce a much softer mortar than that produced by todays hydraulic material.... also remember that the grade of hydraulic is only 'entry level' strength so 'feebly hydraulic' may well be 'moderatley hydraulic.... this is especially important in areas where quicklime came from chalk and produced a softer mortar. one of the recent d*nhea* publications refers to the improved binding of resultant mortars where less water has been used in the slaking process - the only difference between non-hydraulic hydrate and putty (aside from cost) is the amount of water added to the quicklime in the slaking process - more for putty, less for hydrate.... so hydrate is best? - at least comparable - probably. i have used dry hydrate for years and experienced no failure.... i do not agree therefore with the widespread use of 'modern' hydraulic lime or the misconception that putty is better than hydrate............ cat amongst pigeons!!
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Anonymous
Guest
I know this is rather 'off thread' but can anyone suggest how one should translate ' NHL 2.5 etc. ' to a French builders Merchants ? ' Lime = Chaux' is no problem but the sacs I have looked at here give no indication as to the proportions used and the, usually knowledgeable , staff look blank. Anyone know where I can access a list of 'DTU' (National Standards ) descriptions ? Thanks.
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Anonymous
Guest
Ask a Frenchman
Olivier's e-mail is:
labesseolivier@yahoo.fr
Olivier's e-mail is:
labesseolivier@yahoo.fr