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External pointing


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I did look through old posts but they seemed to all refer to internal pointing. I am about to start on pointing the external walls of our 400 year old Languedoc Mas. I have researched as much as possible and through lots of conflicting information. However I need to start and therefore just want any last minute advise.  I am going to use a soft sand and chau mix of 3 to 1, put in by hand and brushed finish a couple of hours later. I am open to suggestions as to changing this, what do you think?

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Wils, I’ve done almost exactly as you describe over the last

couple of years – although in summer, so I can’t speak about the “time of year”

aspect mentioned in the other posts.

Our Mortar was the original stuff and pretty soft, so raking

out was done with an angle grinder and finger rake – although in places where

concrete had been used as mortar, I used a vibrating drill. The joints were

then hosed out and kept wet.

I used a 3:1,  #2  Sand to chaux mix,( I’ve used #4 sand too, but

on balance prefer the look of the # 2) but with a plasticiser,  bought from the UK,  added. Brushing off was done with a  copper brush at anything from 30 mins to 2

hours after applying, based on drying time. Its wasteful, without doubt, but so

far I’ve spent around €1500 on materials, including €1000 on scaffolding,

compared to €14k from a local company, so I can afford some waste. I’m also re

using some of the brushed off mortar to recover a pounded earth floor in an out-house

The results are just what we wanted in terms of maintenance,

and appearance.  

Get plenty of pairs of good rubberised gloves!

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One of the plus's of lime work over cement, is lime can be collected when brushed off and re used because the cure is slower so you can save even more [I]

Was the plasticiser really necesssary, lime is stickier than cement, only used a plasticers (soap not fairy liquid ) when using a mortar gun.

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Plasticiser makes the mix flow easier, normally needed for cement brickwork to make the mix fatty or is that phat nowadays. [:)] Lime work can use soap, milk or animal fat like tallow to aid its properties and to reduce dusting.

Hydrofuge, makes a mix waterproof, is that necessary on a breathable, sorry previously breathable lime mix?

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I read about using it in Joe Laredo's book " Renovating & Maintaining your French home",

Being a bit of a belt and braces man, thought it was worth doing. The bottle says Hydorfuge mortiers et betons-impermeable dans la masse les mortiers, betons,enduits et chapes. Ameliore la resistance au gel.
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French limestone houses have been and will around a lot longer than Joe Laredo, maybe there is a specific reason for adding the hydrofuge.

Limestone construction allows water to be evaporated away at a high rate (breathable) if you use an additive that prevents this then water may be trapped in the lower levels leading to the degradation of those stones and a costly repair.  People forget that the mortar is meant to be sacrificial and therefore softer than the stones otherwise the mortar doesn't erode over time the stones do and that is much harder and more expensive to repair.

I can understand using hydrofuge with cement because cement holds on to water much longer and in the case of swimming pools etc there is a definite need to block the water from penetrating form either the outside or inside the pool or tiles, pebble, plaster/paint finishes will flake and peel.

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Tradi Blanc, like so many of these mixes contains cement as well which makes a gauge mix and gives the poor qualities of both materials.

Cracking on lime work can be due to the background not being damped down sufficiently so the sucking back causes the mix to dry to quickly and therefore shrink or by too rapid drying from the front in warm or windy weather so a tarp or sacking should be hung over the fresh work.

They may also contain plasticisers to make them flow better from render/pointing guns so calcium stearate etc can be added to reduce the water content which can also reduce the shrinkage cracks.  Unlike cement minor cracks can be re wetted and rubbed to fill the cracks.

Cement based products should never be re wetted so the wastage of material can also be higher as said in the previous post, collect the lime mix which is brushed out/ misses the target [:)] and re use.

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Tradi blanc maybe a cement mix with lime mortar, but its a good concession, if you don't want to use pure lime-mortar....i've used both pure and mixed on pointing and the pure will always work "crack" to some degree depending on humidity, sun exposure etc etc....The amount of cement in Tradi is quite low, around 10% which avoids cracking, it also gives a really nice finish....sure, i cant say what the pointing will look like in 50yrs time, but I've pointed locally in 2004 and it hasn't moved or degraded in any way. I think the lime mortar route is good if you want to be a puritan and you really know what your doing and have the time....in any-case, last time i used chaux-blanche i brushed down 12hrs later to re-seal all the cracks. I'd also go for a fine grain sand, this gives a nice regular finish, respect the quantity of water written on the product you choose, don't over water and over all, make the stones stand out when you brush, if not you see only render and a few stones.....but hey, like they say in French, les goûtes et les couleurs!!!
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  • 2 months later...
Tradi Blanc, by Saint Astier, or if not "Renocal", cheaper but not as good. Or if you are a puritan, Chaux blanc by Calcia or again St Astier.

White sand or the colour you want to use...fine grain.

I usually go for 1 tradi, 2 sand....mix it well, not too liquid!!! a sort of plastic feel.

The Tradi will go off quite quickly (depending on weather conditions), so be ready to brush with a nice assortment of wire brushes.....
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And remember, you want to work around the stones, to make them sit out very slightly from the wall...make sure all the little holes are filled....i jet spray with my aggressive "Kacher" nozzle for stone work, which gets the stones nice and clean....if you're really fussy, you could sand blast, but that's adding a considerable cost.

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It's your wall Big Mac so your choice but chaux blanche from Galcia can contain white cement. St Astier pure chaux and the sand of your choice but a well constructed chaux wall would use mortar with a good range of mix grain sized sand, that's the strongest and most hard wearing and the way I was trained to do it.

Default to St Astier for information.  Using too finer sand increases the amount of water due to the surface area of each grain so also causing higher evaporation which means shrinkage cracks. Like wise using it too wet will have the same effect. It should be a workable consistency, putty or dough like.

Protect the new surface with a plastic sheet from wind, sun or rain to reduce the rapid evaporation of the new mortar and prevent cracking although with chaux you can re work the mix to close any cracks because the set is slower unlike cement included products.

The work of polishing the surface to expose the stones is all that is need to clean up the stone work but don't use anything steel, as that will cause rust marks to a appear.

Pre wetting of the wall is essential prior to starting as the wall will suck out the water from the mix otherwise.  Push the mix in hard to make sure of no voids and less shrinkage issues.  Using a mix without cement means you can save money and material because you can re use, re wet any material that falls out or misses the target. You mustn't re wet cement or it will be weak.

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of course, as said by another commenter - its up to you:

I do the following, have done for around 13yrs and have never had any problems, each to their own however:

- pick out all old mortar from wall, often with jackhammer

- jet spray clean with special power jet

- humidify just before pointing

- start to point with either St Astier Tradi or pure Chaux Calcia (its up to you)

- push in well to really fill all gaps and holes

- trowl back any big excess just after you have finished

- let the area start to go off, but not too hard

- test an area with your brushes and if good, begin to brush back. The mortar should be neither to soft, nor too hard. You should not leave grooves in the joints with your brush.

- clean up the face of the stones if they are a little covered

- recuperate any mix for later use if you are using Chaux pure.

hope this helps.....
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  • 2 weeks later...

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