Re-pointing cellar interior wall - advice please

Our French friend bought his from a Brit builder who packed up and went home, so I had no idea it was a UK tool. He paid €25 for it! Now I wonder where he keeps it? I think it has made a few people green with envy around here because the vast majority of buildings are local lime whether medieval or finished last week. Traditional the buildings were held together basically with mud, but modern work like lining and insulating makes the stuff vulnerable and a few heavy rains... So people are always re-pointing and rendering but this really does cut the time and effort down. The compressor is also good for blowing out the old pointing and dust, so when we start the outside then we'll buy one and hope we are still good friends with that bloke. Then we can play with his toy.

The grey muck was for a nasty blue breeze block wall that was part of his neighbour's wall when he bought his place. He tried filling the cracks and crack mortar then put a coat on so that he could render it. That is when PnuPoint would not play.

We use a pure lime mix (5%DHL) with a complicated mixing method developed over a number of mixes to give a smooth even mix that flows well. I wouldn't let any cement near my stone walls,certainly not in render or pointing as it makes the pointing too hard and risks cracking the stone if the wall moves (as they all do).

I already had a compressor (but they are not expensive) but the Pnupoint did cost about £300 as I recall. I think they are a bit less now. They will ship to France.

The key to success is getting the mix right, unless you do this it is not easy to get the mortar to flow well and this slows things down a lot.

We have limestone of about the same hue as you big sandy coloured patch. Most local river sand matches it to a tee. Thrown in mortar and the top cover over the stones works best thrown for us too, so we work together. She throws, I work in with the longue du chat, she throws I use the smallest pointing trowel, then again with a small round tipped trowel and then the top dressing on by throwing with a large trowel then smoothing straight over. Takes kilos off rapidly and sleep is bliss after a day doing that job! Guess what we are doing next Sunday? Only two more sessions and then we are done, both walls.

Yes, it is a great method, we would use the same but this present bit of work doesn't justify buying a compressor. Hope you are using a nice lime mix, when I helped a friend doing it your way it was great but some of the other work using conventional grey cement mortar he was doing blocked the PnuPoint. Copper bristle brushes are used most commonly here, but a devil to find despite every other person having one... They never remember where they buy them.

Looks good!

We have done quite a lot of repointing. Using a trowel is very slow and hard work.

I use a PnuPoint device which is rather like a very large cake icing device. You fill it with the pointing mix (which needs to be exactly the right consistency - I can send you the detailed instructions for this. Then the PnuPoint is connected to a low pressure air line (you do need a compressor as well) and you just feed the mix into the joints at quite a high speed. Leave it for a couple of hours and then smooth off with a small Langue du Chat rowel and then a light brush with a soft brush. Results below after first injection of mortar and finished result.

Some recipes here

I tried UK style application of mortar with throwing it French style to "plaster" a stone wall. The thrown mortar cracked less as it dried. Luckily with lime mortar you can always smooth over the cracks the next day. I'm not sure if throwing makes so much difference for pointing, and the masons I watched mostly pushed it in with small trowels, after raking out loose stuff and thoroughly wetting out the wall.

Some mortar mixes with lime and different local sands below. The lower part of the wall has an enduit de terre![](upload://eWNgDUhvPuYSEtybyUw00Pr71DF.JPG)

As Brian said, go for a lime mortar be it a batard or not. I’m currently sorting out a damp problem in a front entryway, probably turning it to pierres apparantes after years of it having been abused with cement based products that rectified nothing, just made it worse. In UK people tend to re-point by placing the mortar in the joint via a trowel or small tool. Many craftsmen in France say you have to throw it at the joint to make sure it penetrates as far as possible, sort of like like a harling technique. I’ll be using NHL 3.5/sand for the re-pointing.

You need a chalk-lime render and pointing. Three parts local river sand (sable cru), to one part a mix of a mix of white cement and chalk, you can but a mix (bâtard) or mix roughly half each white cement to chalk. I would treat a cellar like an exterior wall and thus use chaux hydraulique, which perspires less than the other kind chaux aérienne.

Look at this diagram. The external render is probably disproportionately thick. For that out layer just reduce the cement to about one third of the mix to two thirds chalk.

We are doing it at present. In our attic on an exterior wall but inside and the chimney stack and wall which both needed serious repointing and is a slow job with the carpenter in laying floors and putting in the superstructure for insulation. However, it is a trowel job repointing, then using a large trowel to throw the outer render on and then smooth it.

Very satisfying job for when you wish to shut off your mind for a while.

We have done quite a lot of repointing both inside and out. I use a Pnupoint pointing gun which fills the joints right to the back and is really great for filling larger voids which often occur at corners. The joints need tidying up after about an hour or so. Throwing the mortar against the wall wastes an awful lot and makes a mess on the floor. I waste very little and sweep up about half a bucket of waste for about 6 sq metres of repointed wall. The mix is critical if you use the Pnupoint as it has to flow into the joints but not be too sloppy or it will fall out.

Hello Mr Blackmore,
Would you be kind enough to advise me on a mix for the pnupoint?

I will be using Tradifarge, sand, and a dose of sikalatex in the water.

Thank you so much in advance.


Hi Richard

The key to success with the Pnupoint is getting the mix right. I can’t emphasise this enough. My instructions are precise to the point of being obsessional but they are based on my experience and I found that if I didn’t follow them precisely the mix was likely to clog the nozzle. Its important to make sure you sieve out any lumps as they will block the nozzle.

For awkward locations I made a special nozzle using a length of 15mm copper tube bent into a slow curve and fitted to one of the plastic nozzles for the Pnupoint. This allows you to point into awkward corners and underneath arches where the standard nozzle won’t work as the body of the Pnupoint needs to be kept more or less vertical.

I tried various plasticisers and found most were not very good. In the end we use soap, either shredded ordinary white bar soap or, more conveniently, powdered soap for washing wool by hand. Details are in the notes.

You wlll find quite a lot of my thoughts also on the link to this thread which might be helpful.

I have attached the latest version of the notes.

You may find it difficult to get it right at first but if you persevere I am sure you will be pleased with the Pnupoint.

Remember to keep the pressure quite low. I added an adaptor to my compressor to allow fine adjustment of the pressure. About 1-1.5 Bar with the compressor running and the valve of the Pnupoint closed is a good place to start. It drops to about 0.8 Bar once you pull the trigger, Adjust to get about the right rate of flow to suit you, regulate the flow by short pulses on the trigger if its a bit too fast sometimes which allows you to run it a bit faster if you have a void to fill or a wider or deeper gap.

Good luck.


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Thank you so much Mike.

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Hi Michael. Would you mind sharing your notes with me regarding your pnupoint mortar mix. I’m using it to repoint some brickwork that has existing cement and sand joints. Your advice will be greatly appreciated.
Regards Tony.

Hello Tony and welcome to the forum.

If Michael does not respond… there are lots of other who doubtless will chime in…:relaxed::relaxed:

Are you talking about a French property ?? … just being nosy (in a friendly way) :relaxed::relaxed:

Hi Tony

My mix is designed for stone and doesn’t use any cement. You might be OK using cement as long as the bricks are fairly hard but the quantities might need to be adjusted. The key to using the Pnupoint is to get the mix very smooth with no lumps at all and just the right consistency so that it flows nicely but isn’t too slopyso it falls out of the joints.

I have attached the latest version of the notes.

Bon courage.



Michael Blackmore - Contact Using Hop

(Attachment mb notes for using pnu-point (april 2013).24-4-2013.doc is missing)

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Unfortunately SF rejected my email because of the attachment. If you PM me with your email address I can send it to you.


Michael Blackmore - Contact Using Hop

Hi Michael, I’m new here. I’m not sure how I can private message you.