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pointing random granite stone wall.


Alfa

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We're off next week for a week of ecstasy and seafood (abandoning Portsmouth for Morbihan !).

However: work needs to be done !!!

My task for the week is to point our rear wall which is random granite stones held together with the silt from the local river (Blavet). I understand the physics involved - the soft mortar enables the stone to move if necessary - but I'm not knowledgeable about the process of pointing such a structure.

The house is 125 years old and I want to do it right - I've searched extensively and have gleaned excellent info (much of it from this forum) on what to use as far as material is concerned but I could do with some advice on it's application.

  1. Do I make the mix the same consistency as standard mortar ?
  2. Do I clean off the (inevitable) mess whilst wet or wait 'til it dries ?
  3. Can this process be accomplished after lunch considering the influence of the exquisite shellfish and Muscadet available locally ?

I'm not too bad with bricks and cement based mortar but pointing random granite is all new to me and I really do want to do the old pile justice.

Any tips/secrets would be much appreciated.

Alfa.

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Hi

When we did this, it was using a product called - at the time - Durex (sorry). I believe that they've now found a more felicitous name. You mix it up more or less to the same consistency as mortar. Don't try to do much more than a sq metre or two at a time. The reason will become clear later.

Brush out the interstices of the stones to a depth of about 2-3 cms or so. Then wet the cavities a bit. Now slop the glop into the cavities, ending up with it rough finished (fingers) and quite a bit proud of where you want it to be finished. You have to think of trying to end up as if the stones are sticking up out of a more or less plane surface (your jointing) only a trace below the face of the stone. Don't panic about making it all too even at this stage.

Once you've filled in your metre or two, go away and leave it - anything from 2-6 hours depending upon how exposed to the sun and wind it is, and how hot the sun is. It's a mistake to try to repoint in the rain. Every so often, come back and check. To tidy it up you'll need a wire brush. You need to wait till the mortar just brushes away nicely without clogging up the brush. Don't wait until it's so hard that it won't come off at all. This delay can be quite variable, and there's nothing worse tham trying to finish off under the gun, so to speak, which is why you really shouldn't try to do too much at a time.

Anyway, when the mortar is of the right dryness, brush it back with the wire brush until the wall surface looks right, slight variations in level are fine, but try - as I said before - to end up with the feeling that there IS a level from which the stones are just proud.

After you've brushed off the excess, leave it until the morning, and srart again. You can take stains off the surface with a good hard brushing with the wire brush. It's slow old work, but very satisfying.

Best of luck.
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  • 2 weeks later...

hiya

the mix is actually pretty simple... use two and half scoops of (sharp) sand to one scoop of chaux and add water to make a reasonable moist mix... not too sloppy... personally, i'd not use any cement at all plus the chaux / sand mix will give you the creamy finish that i'd assume you'd look for / require. besides which, chaux is important as it allows the natural stone to breathe (thats why its used here).

then work it in bit by bit in between the stone using a normal two trowel process and as it's drying, either wire brush it or use your fingers to achieve the finish you want

- one major tip however is whatever you do, wear gloves as chaux is horrid stuff and will dry your hands out in no time at all...

its slow going and like your previous respondent said, do a few square metres at a time... its very satisfying and actually one of the jobs i most enjoy!

however, after lunch of shellfish and wine... hmmm... well, i'd recomend starting early morning and rewarding yourself with the shellfish and glass of the well chilled when the boss congratulates yu on your hard wrk!

best wishes

neil - brantome (24)

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hiya

the mix is actually pretty simple... use two and half scoops of (sharp) sand to one scoop of chaux and add water to make a reasonable moist mix... not too sloppy... personally, i'd not use any cement at all plus the chaux / sand mix will give you the creamy finish that i'd assume you'd look for / require. besides which, chaux is important as it allows the natural stone to breathe (thats why its used here).

then work it in bit by bit in between the stone using a normal two trowel process and as it's drying, either wire brush it or use your fingers to achieve the finish you want

- one major tip however is whatever you do, wear gloves as chaux is horrid stuff and will dry your hands out in no time at all...

its slow going and like your previous respondent said, do a few square metres at a time... its very satisfying and actually one of the jobs i most enjoy!

however, after lunch of shellfish and wine... hmmm... well, i'd recomend starting early morning and rewarding yourself with the shellfish and glass of the well chilled when the boss congratulates yu on your hard wrk!

best wishes

neil - brantome (24)

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