Rendering a stone wall for less than €17 (Yes, seventeen!)

Sorry to push Tiez Breiz again. but I hosted a course of theirs on sand a couple of years ago (and got some rendering done for free as a consequence). It is really worth testing your local sand with different proportions of lime before you start. Put little tests on a wall or on some chip board, and leave to dry. Say dinner plate size, 1.5 cm thick. Too much lime and it is too hard, too little and it's too crumbly, too much clay content and it cracks as it dries. The tutor made me get samples from local quarries and his chosen and successful mix was 3 parts washed sand, 3 parts unwashed sand (which had to be sieved to get the sand out) and 1 part lime. Obviously more sand to lime is cheaper. The clay in the unwashed sand is contributing to the mix. The tutor brought samples of other sands and challenged the professional masons on the course to assess the sands and produce successful mortars. A granite sand mix was 2 sand to 1 lime, since there was no clay content, and a very low proportion of fine sand. The application is also significant. I used what had been a nice workable mix on walls for pointing a slate floor, but it was too soft and wore away.

Their publication:

1 Like

Yes, same mixture for outside.

PVA might well work, give it a try on a small patch first. :)



Would this lime mixture be exactly the same for outside work ? ...I have a small area where I could practise this next Spring.

Internally, I have a utility room which I think has been lime rendered...badly, I think as it sheds a lot of sand & dust, which I keep having to sweep up. Would a coat of dilute PVA be a good enough way to stabilise the surface ?

Thanks, Hilary, Dordogne.

Lime plaster/render is good for the fabric of the building as it will allow the wall to breathe not trapping in moisture. Boarding over it with plasterboard (BA13) would work fine if it was done correctly and ventilated. If the wall is particularly damp then that should be addressed in either case.

Very helpful -and very detailed -well done.

From what I understand from the comments - the railed 'plac a plac' method/system is not friendly to the environment of humans - some form of lime plaster straight on to the walls is better -is that correct?


1 Like

Thanx James as always Spot On!

1 Like

It's an enduit de finition. Presumably an enduit de finition fin et lisse a la chaux. I did it on my mud/hemp walls which otherwise looked like mushroom painted woodchip. The mix was 2 vol of sieved sand - less than 2 mm, there is a fine white sand (0/2)available from a quarry near me, to 1 vol lime (CL90). You mix it quite sloppy, let it mature for an hour or two, apply with trowel. I lime washed after.

Sand is apparently necessary on mud/hemp because it moves more than lime hemp, so you might get away with just limewash, painted on, troweled smooth, but I'd want to test.

We are looking at lime and hemp insulation for our the internal stone walls of our house - I would like a smooth finish - like a topcoat skim in lime plaster - anyone know how I ask for this in French?

please bear in mind that the over 40% of the heat loss on old building can be infiltration (leakage) which is why new"double glazing" has such an effect - not because the glass is so good but the leakage is much reduced. The difference one may get from a lot of insulation on walls might not be very much in relative terms. Controlled air for open fires via tubes/ducts if a good bet.

Simplest way in France is Hemp and Lime plaster on the inside or a Mineral insulation system eg Multipor outside or inside In reality a 60cm + wall built of stone and coated with a proper lime plaster inside and out with a breathable paint has a good insulation value most walls tested were cement plastered and damp which accounts for the bad values If you look at the true figures you will find that it is more eco friendly to install a proper eco heating system than to ruin the house and you health with all the petro cem products The Scottish court service did extensive testing on their buildings and found that the prewar building preformed better

Thanks Edwards. I'm hoping the dampness is a temporary problem. The previous owners covered over an old external door with a sheet of plasterboard. The door was ill fitting and let all the elements into the space between the door and the plasterboard (they didn't fill it with anything). It seems to have been absorbed into some of the wall. Or the combination of that with the crumbling pointing outside. Anyway, I'm hoping once a window is properly fitted where the old door was, and the stonework pointed outside, the problem will be overcome.

How do you recommend insulating stone walls Edward?

Valerie I would not dry line my worst enemies house approx 33% of dry lined houses have toxic mold growing behind the dry lining You have to do away with the source of damp on the outside You can get away with the wrong plaster inside a house if you have the right plaster or pointing on the outside Look up Toxic Mold

Hi Edward, I've removed our link as we don't allow that. So is my NHL 3.5 okay in environmental terms or could I do better?

Can you supply your products to France?



Our company is Traditional Lime Co Ireland. We are the agents for St Astier in Ireland All Natural Hydraulic Limes are different anyone who tells you that their lime is the same has a very limited knowledge of limes As all the limestone deposits vary so does the lime Contrary to popular belief CL90 is not the most eco friendly a 3.5 NHL is If anyone needs advice on Limes Mortars or Paints please feel free to contact me

This is what I used Edward

Hi Edward - is that your company? I have a (vague!) idea you do something similar?

I've normally worked with what used to be called Chaux aerienne pour les batiment (CAEB) now CL 90, occasionally, for greater hardness, Chaux hydraulique NHL 2, 3.5 or 5. This site explains,, and it's true that some hydraulic limes have cement added. I buy from Point P.

The reason I wanted to know the exact spec on the bag to see if it was a true natural lime or a Lime OPC mix When we tried to get local masons to work on our house everyone of them swore they only used Lime but when asked which one it turned out to be a Lime OPC mix labeled Chaux for good english specs on lime go to

Good to remember that Alex. Ask locals who use traditional materials. Here near the Dordogne river it is April to early May then again October to beginning of November for all external work and never indoors when it is over 35° and totally dry. It naturally varies place to place. We took so many notes about details like that, that we should get it right. The fine sand for the inside finish is a good tip, it will join the other notes.