Pointing old stonework.

My son has a cottage in Scotland about 150 years old which he is bringing back to life. The structure is a solid wall built about 24 inches thick built with what I would refer to as, random stone and lime mortar. Many of the joints have fallen out over the years and it is allowing water to work its way through it. His local builder has suggested raking the joints out, pointing the gaps with sand and cement and then pebble dashing the walls with a sand and cement mortar.
I looked up some solutions offered for this problem and found suggestions such as repointing the wall with a natural lime mortar because sand and cement mortar may not adhere to the original lime mortar.
I have a number of questions:
1. Would sand and cement with plasticiser work as a pointing agent and not conflict with the original natural lime mortar?
2. I remember seeing bags of lime back in the 1950s which was used with cement and sand to create mortar. Is that sort of lime the sort that one uses to make lime mortar?

Im no expert but if its that old, you need to replace like for like. So a lime and sand mortar. As the wall will need to breath. Someone whos better at lime will comment more.

Have a read

http://www.stastier.co.uk/nhl/guides/ptgnhl.htm

Use a lime based mortar.

Many thanks for the advice. I served an apprenticeship as a Bricklayer in the early 1950s when Lime Mortar had stopped being used being replaced by bagged lime mixed with cement and sand. However, I was lucky enough to see the construction of Nuffield College Oxford as a boy and I watched them actually slake lime to create lime mortar.
I will now be able to advise my son to tell the chancers who suggested repointing the building in sand and cement to take a walk and if necessary I will dig my tools out and do the job myself hoping to avoid the Scottish Midge season.

Well said, BML. Don't let them (or cement) anywhere near it!

You can either slake your own lime if you know how or else buy it from all sorts of people e.g. Mike Wye (although they are at the far end of the country in Devon), Ty Mawr (Wales) and lots of others on google. Sort the causes of dampness and let it dry out naturally.

Definitley replace like for like and avoid cement like the plague.

I'm in a similar situation (100+ year old random stone cottage) but not quite at the rebuild stage yet - just some repairs.

If the stone is in good nick, then you can probably repoint. This would be the preferred route from a conservation point of view - do as little as you need to. And a random stone wall freshly repointed in lime looks fantastic.

If the stone is in poor condition and building is in an exposed location (i.e. soft sandstone rubble) then you could always repoint in lime then lime render to give the stone protection from the elements.

A good supplier for lime products & tools in Scotland is http://www.masonsmortar.co.uk

Go on a on a basic lime training course - give the Scottish Lime Centre a call, these guys are fantastic: http://www.scotlime.org/.

I'd start with their basic pointing course, this is a great introduction and he'll be able to go back and look at the building with a totally different eye.

If you can't make it onto a course, then take a look at these DVD's: http://www.themasterstroke.com/

You don't need to slake any lime for this job - slaking will produce lime putty which is not very durable and only really suitable for internal work (at least in a Scottish climate). You would use bagged natural hydraulic lime powder which is available in a range of strengths depending on the situation. Mix with appropriatley selected sharp sand and you have your basic lime mortar.

One of the most important things with lime is preparation and initial looking after. Lime is a lot more expensive then cement so the last thing you want to do is make a mistake - that's why even a basic training course is essential. A few hundred spent on training is a drop in the ocean when you think of the time and money you're going to spend.

Could ramble on all day about it, let me know if i can help any more.

Cheers,