See also articles on specific techniques for repointing stone walls, and materials – lime, sand etc – to use.
A pointed wall is dry, naturally well insulated, and provides protection against the insects and small animals that will otherwise enter your house through the walls. Old unpointed walls can look nice and rustic, but that doesn’t make them funny to live with when you have an invasion of flies in the house and a heating bill twice as high as it should be.
They are also dusty and grimy, and impossible to keep clear of cobwebs etc. So I assume that you will at some point want to tackle the task of pointing them.
Specific techniques will vary according to your location since the type of stone available locally determines the building process used. The broad principles will always be the same however.
The first time I pointed a wall, I carefully researched on the internet and in books, and learned that I should remove all visible stones less than about six centimetres across, and also that the final result would look better if, where two large stones touched each other, I created a groove. Fascinating I am sure but having watched the mason at work I am now taking a more free and easy (and hopefully traditional) approach – if a stone is small and loose it comes out, otherwise it stays. And no effort to carve grooves between large rocks, which is frankly a complete waste of time and effort, and has no visible effect on the finished product.
I have assumed that the wall to be pointed is structurally sound. If it is not, you will need a mason to repair it before you start. Underpinning and subsidence are beyond my knowledge and in any case are rarely tasks to be tackled by even the most enthusiastic amateur.
It is worth remembering that lime should be used rather than cement for all jointing type work, be it floor tiles or the stonework of the walls of the house. There are several reasons for this, including (in no particular order):
- The manufacture of cement is very environmentally unfriendly
- Lime can breathe better than cement so is better for the building, but will still prevent rain and water entering the building
- Lime doesn’t crack or shrink in the way that cement does, and will automatically fill any little cracks that do appear, so lasts better
- Cement is very hard and extremely difficult to remove from old rocks and tiles, hence the next time these are worked on they will probably need replacing rather than simply cleaning, if lime has been used it can be removed quite easily
- A cement mix will tend to be harder than the tiles and stones, so these can crack if any slight movement of the structure takes place. A lime mix is softer that the tiles and rocks so will not cause this problem.
You can see that I am not a big fan of cement. To be fair to cement, the Renocal I refer to below is mostly lime but does contain a small amount of white cement. It is quite common for a small amount of cement to be added to lime to give it a bit more strength. Never grey cement, always white cement.