Repointing walls – a factsheet awaiting your contributions
2nd August 2006 at 23:04 #778963
That’s excellent! A really good guide. If the French masons are doing it that way then it sounds good to me.
How much sand is in a bucket? Presumably the bag of lime is the 35kg weight? And approx how much hydrofuge do you add?
Knowing the measures will help us to get the mix just right.3rd August 2006 at 19:00 #778964
thebeansParticipantJoined: 11 May 2006Location: Cantal, AuvergneTotal posts: 289
The bucket is a standard size french builders bucket (not the larger size you sometimes see) i think they hold about 10 litres of water. The lime is 35kg. I think the brand we use is called saint astier, it might be regional i am not sure. It comes in a blue sack or a green. The blue is very white and the green more of a dull white, not so bright. The hydrofuge is 70ml to 35kg, i normally aim towards 100ml just because its easier.
ps. Just level the sand in the bucket off flat with the top.
So one morning they awoke & found themselves many miles from home... My oh my, what had they done!!!3rd August 2006 at 19:13 #778965
Thanks … just what was needed for the calculations.6th October 2006 at 20:36 #778966
anonymousParticipantJoined: 23 Mar 2012Location: N/ATotal posts: 751
I work with a French artisan who is a specialist in the use of Chaux (lime) and we have just finished pointing the outside of a converted barn.
We used St Astier lime which is indeed regional – based at St. Astier I suppose. I live in Haute-Vienne, but work in Dordogne, and (by sheer coincidence) passed next to the plant on the way to Bordeaux last week.
We used a St. Astier lime called “Tere chaux”. which is slightly hydraulic (NHL2). As the name implies (from Terre i.e. earth), this is intended to be used over supports such as Torchis (earth and straw). Anyway, my boss says it’s good for surfaces that may be subjected to some movement (it’s a fairly soft lime). I guess that’s why he chose it for pointing the old barn. Other types of lime could, I’m sure, be used with success. Have a look at the St.Astier website (http://www.c-e-s-a.fr/).
We also used a liquid waterproofer (impermeabilisant) which comes in sachets (add 1 per mix). You’d probably find it easily enough from the likes of Point P. Tell them it’s for an “enduit” or “crepi”.
The sand we used was, I suspect, just whatever they had at the local builders merchant at the time. Be sure to get as much as you need to finish the job, as their next batch might be a different colour. Another thing we did, possibly not essential, was to add 2 buckets of ‘sable argileuse’ (sand with a lot of clay in it) to every mix. It may not be easy to get hold of.
The resulting mix was wonderfully sticky and pleasant to use. I forget the exact dosage of sand/lime, but this info is printed on the bags of lime anyway, so you can’t go far wrong.
The old mortar was removed with pneumatic chisels (small and light) and a large industrial compressor (hired). It may not be cheap but you will get the job done much faster and save a lot of hassle, unless you are doing a very small area. I find the electric hammer chisels are very tiring to use and, on a previous job, seen even Makita chisels ruined after several weeks of daily use.
The stones were then cleaned using a pressure washer. This also helps clean out the joints and moistens the wall in preparation for the mortar.
To apply the mortar, I flicked it on using a small diamond shaped trowel, as I found this helped to get the stuff well into the joints. You can apply it ‘normally’ though by pressing it on with a trowel. Don’t be sparing, just try to leave the bulk of the bigger stones showing through. It’s OK to cover up completly most of the stones, but not under a super thick layer!
Don’t bother trying to re-use the mortar that falls. It may be dirty, you waste time, and anyway there will inevitably much more waste later on when you brush the dryish mortar off. It may seem that a lot of mortar falls to the floor but, with practice, the vast majority will have stuck to the wall.
Once the mortar has dried a bit you can start to brush the excess off. You may be able to do this on the same day or you may have to wait until the day after. It will depend – I expect – on the weather, how damp the wall, and how thick the coat is. I used 2 grades of scrubbing brushes. One hard (steel bristles) one softer (brass bristles). Brush vertically or diagonally to remove the mortar and reveal the stones. Once found, brush the mortar off the stone. The emphasis is brushing the stones, not the mortar, but in practice a bit of both is required. Finish with a softer brush, the type you normally use with a dustpan for sweeping up.
As an aside, the Chaux aerienne that you buy in sacks for decorative finishes has already been ‘slaked’ with water and will not generate lots of dangerous heat when used. You can, so I’m told, still buy Chaux Vive which then has to be extinguished in water, then filtered, etc. It may be an interesting exeriment but probably isn’t worth the trouble.
We also use lime called “Chaux Aimos” which comes in buckets and has the consistency of Creme Fraiche. It’s very pure, very white and makes a very economical limewash paint when mixed with water. It can also be used as the basis for other inerior decorative finishes and easily coloured with pigments.
People may instinctively reach for sacks of cement when renovating, but your old barn was probably built without any cement!7th October 2006 at 08:44 #778967
Tremendously useful! You write with an air of genuine experience that will give confidence to anyone reading. Thanks for that.
I have also used a pneumatic chisel for cleaning out joints and can vouch for its efficiency.18th October 2006 at 18:48 #778968
We need to repoint the sides of a stone wall after having knocked an opening through it. We plan to use chaux hydraulique and sand but would like to know if there is any special technique to mixing it up – or is it just like making cement in the mixer?
Kate & Ron
~ in vino veritas ~18th October 2006 at 18:56 #778969
If you look back over the previous posts above I think there are several references to mixing, which i think you can do manually or in a mixer, according to your preference. Don’t take my word for it though!18th October 2006 at 19:13 #778970
Hi Finlay – I have searched the forum and the internet in general but not found anywhere where it says how to mix it in a mixer. I had heard that you can’t add water to the chaux – it must be other way around – but maybe that’s for a non-hydraulique grade? Can I assume then that you mix the chaux and sand together and then add water until it is of the right consistency. How long will this take – I’ve heard it can take up to 30 minutes to mix – is this right?
~ in vino veritas ~19th October 2006 at 07:54 #778971
petercherryParticipantJoined: 02 Sep 2005Location: Derbyshire & La CreuseTotal posts: 40
I’m not an expert at mixing Chaux, but when I use a mixer, I firstly put water in to clean it, then add some sand, then some cement. I would assume that you just substitute the cement for the chaux i.e. not actually putting it straight into the water. I would suggest measuring in buckets though to get the mix consistent ..
Peter19th October 2006 at 16:13 #778972
looking_dreamingMemberJoined: 03 Jun 2006Location: N/ATotal posts: 3
I would do sand and lime first then water. You want quite a dry mix with lime mortar – and it needs more knocking up than concrete would. You can easily overwater it.
I dont use a mixer, just mix by hand. I do say 3 sand 1lime, 3sand, 1 lime, and so on until I have the quantity right, just helps the mixing donw like that then add a little water.
Of course if you use putty rather than dry lime you might not need any water – but the mixing will be harder.19th October 2006 at 18:28 #778973
Thanks both – we’ll give it a go tomorrow!
~ in vino veritas ~1st November 2006 at 21:52 #778974
misterMemberJoined: 01 Nov 2006Location: N/ATotal posts: 3
Hi, first time poster – so be gentle with me! I’ve just returned from France having employed a local artisan to reconstruct, in stone work, a collapsed wall / window and repoint the front and rear of the building. I admit to knowing little about traditional building techniques and am somewhat in the hands of this builder ( who came recommended by a number of local people ). He has used a combination of sand plus ‘Calcia Technocem 32,5 Ciment Gris multi-usages’ and ‘Calcia Baticem 12,5 Ciment a Maconner’ to rebuild the collapsed wall, and repoint the stone work ( which I believe is granite ). Having read on this forum, and others, the importance of using lime mixes on old buildings, I am beginning to wonder whether this chap has used the right materials! Nowhere on any of the Calcia bags does it clearly state Lime ( or Chaux ), and I’ve been unable to find any definitive information online. I am worrying unnecessarily? I would very much welcome the advice of anyone who has used these Calcia products.1st November 2006 at 22:12 #778975
peakeMemberJoined: 21 May 2004Location: Plouasne, Dept 22 & abit further East than JennieTotal posts: 228
Welcome to TF, try this site it should give you all you need to know1st November 2006 at 22:30 #778976
misterMemberJoined: 01 Nov 2006Location: N/ATotal posts: 3
Peake, hi, thanks for your prompt reply. I’ve had a look at the link you kindly posted, but with my limited French I am still not very clear!2nd November 2006 at 13:01 #778977
georgeParticipantJoined: 29 Jul 2003Location: Kent & 72Total posts: 1
Peake, hi, thanks for your prompt reply. I’ve had a look at the link you kindly posted, but with my limited French I am still not very clear!
There is an english language version, just click on the flag at the bottom of the page
George (Kent & 72)