Pointing a stone wall

Many older French properties will contain at least some stone walls, often they have been rendered or plastered over or have been covered in timber cladding. It is well worth exposing some of them as they add a lot of character and warmth.

Chipping of the old render in this case was easy, it was very loose and came of with hand tools mainly.

Repair any big cracks with mortar before you begin and using a lime based mortar push the mixture into the gaps, get it all the way in. It's best not to have raked out too much of the joints, 3cm is enough.

It's a slow and tedious process, but it's not difficult, the lime and sand mixture remains workable for a long time.

Keep the wall very moist, this will help the mortar to adhere and stop it drying out too quickly which can result in cracks.

After a few hours you can use a wire brush or wet paint brush to smooth out the pointing.

The mortar will have a green tinge to it for some days to come due to the lime content, it will eventually dry out and become the same colour as the sand you used.

I prefer only to do this to interior walls as I like to insulate the others.

This is a nice and easy DIY project, cheap to do too. Make sure you wear gloves though, the lime is corrosive!

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Probably at least 4 or 5cm. Depends on the state of the existing mortar too. Remove whatever is loose and get as much as you can pushed in there.

James,
What would the minimum depth be to get a decent finish?

Hi Jo

It's the same mix that I used here when I rendered a wall.

James

Hi!

For future reference... please would you tell me what the French lime product is called? Also, which sort of sand would you recommend? My building has been pointed on the front facade, but only a third of the way up!!!

Another thing... I'm not good with heights!!! Is there anyone out there who would consider a work exchange? I have two really nice bed and breakfast rooms, I practice Sports Therapy, and I'm a great cook... things to consider in exchange?!!! Thanks!

Thanks Clare, you can also mix pva in with the mortar as I did here, although it does diminish the breathability of the wall. Would love to see some photos if you have any?

James

Love pointing as it transforms the place. I agree about the gloves as well. I have used lime and tradifarge and prefer the latter. I also seal ours with a 5 part water to 1 part pva and brush it on as this stops it shedding after. good work

Excellent, hope your project goes well!

Nice one James, just what I need to read and see, stone wall lime pointing demystified! Thanks.

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You can buy it ready mixed (mortier) and you will find many products to do this (have a look at www.weber.fr), just ask at your pro builders merchant, but it's much cheaper to mix it yourself, 1 part lime to 3 parts sand. Don;t hesitate to ask if you have any questions!

Is the lime/sand mixture sold ready-mixed in sacks? What is it called, please? You have explained it so well that I may try it. Nice post. Thank you.

I have done this on a couple of walls in my house, which is pierre apparente on the outside. I have also done lime plastering but that is more time consuming. Has anyone tried panelling?

Thanks! I have a free slot in 2023 I think :)

When you've finished your place James do you want to come and do ours? You're doing a great job.

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We live in a high 'calcaire' region, some of our internal walls have a white fungus type growth and the stone underneath is crumbling in places. Has anyone any idea what to do about this? I brush it off but it forms again.


Hi! So impressed by your description, that I'm about to test my skills (68 year old grandma!) on a tiny garden wall first. Any tips to get outdoor stonework clean of black lichen-like staining in places? Wire-brushed it, scrubbed it with Anti-Mousse, still looks dirty against new pointing.

We have this on our fireplace, and would also be interested in any advice. I'll upload a pic when my camera is charged.

When buying lime for work on houses built with lime mortar or clay, you must make sure the bags you buy have NHL before the number: NHL 5 . NHL 3.5 and NHL 2. Bags marked HL or FL are not suitable for work on these types of houses, because they have white cement added. Their use if for modern buildings. The specs were revised about 5 years ago, and companies selling supposed NHLs with a "Z" following the 5 and 3.5 were forced to drop the "N". The "Z" stands for added cement. NHL 5 is for supports, 3.5 for lighter supports, pointing and renders. 2 is for renders, both internal and external. There is a 4th lime which isn't hydraulic: chaux aérienne. In Eire and the UK it is called Hydrated lime, and mostly used for limewash. It will not set in the presence of water, as do the NHLs. In the UK and Eire, hydrated lime is often mixed into a cement mortar to soften it, and some expat 'Calais" builders mistakenly use the lime off the shelf, here in France, which isn't the same, causing severe damage to the older housing stock. The reason cement mortar shouldn't be used on the older houses, is because it has the same characteristics as steel: it expands and contracts. This causes cracks and tensions, which disturb the older masonry. Cement mortars are also extremely dense, and cause a build-up of moisture in the older walls. By the same token, it causes problems, when used to point, which results in the surrounding stone-work to decay. Saint-Astier, CESA, based in the Dordogne, makes probably the best quality NHL Natural Hydraulic Lime. They do make a ready mixed NHL 2 mortar, which comes in a choice of pastels (for external appearance) but have one for plain work. Really speaking, NHLs should be 1 lime to 2 or 2.5 sand. I have written a book on the subject: A beginner's guide on the use of lime in building. 10% of it can be downloaded free, which will give you plenty to think about. It is in eBook and hard copy formats. Vincent Flannery

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We only get this on the fireplace. None of the exposed stone walls have it at all.

Your work looks great James. When I asked for this 'pierre apparent' to be done by the builders who were renovating my holiday home, they looked at my me like I'd gone quite mad! They used some sort of spraying machine that did all the new pointing in a fraction of the time. I'm really happy with the result, they did a great job.