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Pointing stonework


annie
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Hi Ok

                  I find Renocal mixed 3.5 / 1  will give you a better finish than just pure lime  ...the colour is dictated by the sand unless you fork out for the pre mixed stuff

    [IMG]http://i83.photobucket.com/albums/j311/daveolive/render/PDR_0110.jpg[/IMG]

   Dave

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[quote user="Théière"]

Hi not ok,

Renocal = 2/3 chaux + 1/3 ciment the expensive way and gives you a worse mix of both worlds don't use it.

I could spend an entire evening finding loads of links to Not add ciment to chaux........

http://www.lime-mortars.co.uk/articles/cement-and-lime-mortar

 

[/quote]

 Hi Ok

   With only  42 years of working with Welsh stone buildings and only  7 years with French ones I kowtow to your knowledge

                             Dave  

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I use Renocal, mixed at between 2:1 and 3:1 depending on exactly what aspect of the finish I'm aiming for. The less sand the whiter the finish, but I prefer a more off-white/creamy look. The product is on the list of recommended mortars specifically intended for the restoration of old buildings, national treasures. It was recommended to me by my own builder. It is expensive but I find it very easy to work with as it has a plasticiser added, so it's ideal for a dedicated amateur like myself. To sum up, if it's used by the local French artisans, it's good enough for me. If I didn't do the job myself but got someone else to do my pointing the odds are that I'd get the same product applied anyway.
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Of course, renocal is popular in deux sèvres due to its promotion by the large Calcia Italcementi operation at Airvault.

But any company producing chaux products with an italian background is bound to be good.

Renocal is a good product for inexperienced artisans and amateur chaux enthusiasts and will give good to excellent results even for a neophyte.

http://goo.gl/k80d5

http://www.ciments-calcia.fr/NR/rdonlyres/AEDBD14C-90A1-4AAD-B969-35430058E3C7/0/Chaux.pdf

Depending on use I will use products produced by Calcia, Lafarge and St Astier as suitable.

I have just completed some 100 m2 of internal pointing and enduit in a 17th century barn and for this I used exclusively a St Astier Tradilege Natural Hydraulic Chaux mainly because at Leclerc in parthenay it was almost € 4 a pocket cheaper than similar products from Calcia and Lafarge.

As to colour there are two possibilities, one to add a natural earth colorant to the mix when the colour of the sand is of little effect or to lift the "laitance" gently from the surface just before the initial "prise", either with a soft brush or a sponge, to reveal the natural colour of the sand contained in the mix.

Sand colours will depend on the local supply but for example, sand from la loire is light coloured, sand from la vienne is slightly yellower, sand from the cher is beginning to have a slight reddish tinge. A sand with a granulometric size range les than 2mm will be more amenable to a common 2-4mm size range. Do not use under any circumstances that which is called a "sharp" sand.

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Hi Pacha,

 

I am intrigued as I would have imagined that coarse / sharp sand would have been what was used in the construction of our buildings...certainly the the mortar where it has dislodged is very 'gritty' and I would have imagined sharp sand would have lent more 'body' to the mix?

Are you recommending 'soft' sand and if so why?

Cheers...

Mac

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Hi Ok

                       the size of the sand  should be a % of the gap you are trying to fill .

                                                                    Dave

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[quote user="BIG MAC"]

Hi Pacha,

 

I am intrigued as I would have imagined that coarse / sharp sand would have been what was used in the construction of our buildings...certainly the the mortar where it has dislodged is very 'gritty' and I would have imagined sharp sand would have lent more 'body' to the mix?

Are you recommending 'soft' sand and if so why?

Cheers...

Mac

[/quote]

By sharp sand I was thinking of something like this

[IMG]http://www.wickes.co.uk/content/ebiz/wickes/invt/220112/Sharp-Sand_medium.jpg[/IMG]

The OP with internal work is likely to be doing "pierre apparente" rather than "rejointement" ( pointing in english). Where you live the local available stone tends to be schist with its longest dimension laid horizontal and a repointing technique will be used. Other areas of france have for example in La Vienne a tufaceous rock which is laid similar to schist but the repointing is done with a local clay with the material between the stones left some 2 cms from the outer surface to protect it from the rain. The "moellons" of deux sèvres are irregular in shape and irregular in size and lend themselves to a "pierre apparente" technique where the smaller stones are concealed allowing the larger more aesthetically pleasing stones to stand out. Any attempt to point this irregular material results in a fussy christmas pudding texture to the wall. The core material of a wall varies from a clay to a clay-sand-lime mixture. The quality of the lime used is very variable as it was made in a simple vertical lime kiln with charcoal; often the slaking process on site was very rudimentary.

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Hi ok

               Failing to find a Wicks in France  I tend to use 0-2 for the render and 0-8 for the pointing ,you can the sieve out the larger stone for the pointing 

.... Dave

[IMG]http://i83.photobucket.com/albums/j311/daveolive/P1000283.jpg[/IMG]

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[quote user="BIG MAC"]

Hi Pacha,

 

I am intrigued as I would have imagined that coarse / sharp sand would have been what was used in the construction of our buildings...certainly the the mortar where it has dislodged is very 'gritty' and I would have imagined sharp sand would have lent more 'body' to the mix?

Are you recommending 'soft' sand and if so why?

Cheers...

Mac

[/quote]

Pointing/building with lime requires a good mix of sand to produce the strongest yet flexible mix, sharp sand is one of the constituents but by itself hasn't enough fines to produce the best work.

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  • 3 weeks later...

That's what I thought Theiere....I would have thought that small stones would have been wedged in the larger gaps and the 'pointing' flushed over much the same as in the UK. The stones employed in this way provide a mechanical strength  not achievable in a lime mortar alone. Cheers

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