How to Repoint a Stone Wall
A step-by-step guide to repoint an old stone wall
In 2002 we bought an old stone farm house complex in Limousin, South West France and over the years renovated it to create a gite and Bed and Breakfast business. This entailed a great deal of renovation and repointing of the walls which were made from 'moonstone' or stone from a giant meteorite that landed in the region near Rochechouart. Since then we have moved on to new projects, but still in Limousin.
The techniques shown here are tailored to the local style of building and we kept a keen eye on regional variation and traditional techniques but much of what I outline below can be adapted to any stone walls. My aim is to explain exactly how to repoint an old wall.
Why point stone walls?
There are several reasons to point walls and they include:
- Making the house weatherproof - stopping water anddamp getting into the wall
- Stopping insects and animals nesting and living in the walls
- Making the house look attractive
Maintaining local traditions and techniques
Use this as a guide to re-pointing in Limousin, France and you can follow it exactly. If you're in another region or another country, do please take a little time to find out about your local area, the traditions, local materials and regional styles. Your planning department will help you. Keep your eyes open and look for examples of good practice.
'Monsieur' Batiments de France (this is what one local builder called them) are a group of architects whose job it to preserve the traditions of the local architecture. They helped us most by specifying the colour of the chalk which matched almost exactly the colour of the render on the adjacent barn. Builder's merchants also keep a book with the regional colours in it. For our second house we took a sample of the original mortar and found the closest match. The pointing in our second house was much more yellow than the first.
In our area the pointing is flat and as near as possible on the same plane as the stones. You'll find other variations in the way the mortar is applied and finished. Please do carry out your homework.
Our First Project
Our farm house in Limousin
The farm house we bought in Limousin had been rendered - I suppose to give it a nice, clean, 'modern' look. The photo below shows it at it's best but in reality it looked tired, stained and old-fashioned. We removed the rendering, sandblasted the walls, dug out old, loose pointing and re-pointed the whole building.
Before - the house had been rendered
After - The finished product
Stones from the meteorite
Tools and Materials
Tools you will need to repoint a wall
- Wheelbarrow, container or cement mixer
- Spade if using large quantities
- Wire brush
- Small pick and perhaps an electric drill
- Safety goggles
- Something to spray water, either a garden sprayer or a smaller hand sprayer
- Scrubbing brush to clean materials
Materials you will need to point a stone wall
- Builder's sand (dry)
- Coloured chalk* See below for more discussion
- Stone and/or old clay roof tiles to fill gaps
A note on the importance of the right materials to make the mortar
All my experience of making the mortar for stone walls has been in France and the materials certainly have different names in French than English. I am also uncertain if there are similar materials in the UK or other countries, but the rules will be exactly the same. You need to make a soft lime mortar so tell your planning officer or builder's merchants what you would like to do and let them advise you on the materials. The 'recipes' seem to be somewhat complicated - here's what Cathedral Communications has to say about lime mortars.
Do not use cement
In France they have only one word - Chaux or chalk - to cover a number of materials including lime and chalk. The mortar should be a lime mortar and should not be cement based. Cement is hard and can cause damp problems if the walls are unable to breath.
The correct colour
We used coloured chalk to match the original colour of the pointing. I'm not exactly sure what the people who originally built these stone houses would have used. I guess the subsoil. Digging in the garden I have noted a very ochery coloured sub-soil. You may be able to get sand that will give you the correct colour without going to the expense of buying coloured chalk. We did several experiments on small patches to make sure that we achieved the correct colour. You can also buy tints to colour the mortar yourself but you may run the risk of patchy colour if you don't get the quantities exactly right.
A note on the importance of weather and temperature
The work must be done when the temperature is between 5° and 30°. It is better if the weather is mild and not too dry. Avoid working in hot, blazing sun or very low temperatures. A nice, warm sunny day is good for you and good for the wall.
I'm not sure that it would be a good idea to work in the rain either.
Preparing the wall
Removing old pointing
Prepare the wall carefully
Use a small pick to chip out or rake out old pointing or, if the pointing is hard or if cement has been used you might need to use a drill to dislodge the old pointing. Don't remove too much, a couple of centimeters should be enough if the pointing is hard. Do remove all soft and flaking pointing.
You can see on the photo below the top section has been removed with a pick but in the section below the pointing has fallen out or been worn away by time and weather.
If you take out more than you need to, it will cost more in materials to fill it up.
Preparing the mortar
How to prepare and mix the mortar
- Use a ratio of 1 part chalk to 2.5 parts sand. I found it easier to think of 2 parts chalk to 5 parts sand.
- Put dry sand into your wheel barrow or cement mixer. I used a wheelbarrow and found that ten measures of sand in a 30 cl creme fraiche container was enough for me to mix by hand. If you are using a mixer, you would probably measure in buckets. So long as you maintain the ratio the mixture will be good
- Add your coloured sand and mix the dry ingredients well with a trowel
- Add water carefully, bit by bit until the mixture resembles the topping for an apple crumble but is paste-like when you press it (see illustration). This is practical rather than critical - the mixture should be soft enough to handle but not so soft that it drops off the wall. You'll soon get the hang of it. Start with a small mixture and see how it goes.
Measuring the chalk and sand
Mixing in a wheelbarrow
The right consistency of the mixture
A note about timing and quantities
Make sure that you do not mix more mortar than you are able to apply. A rule of thumb is that you can do about 6 M2 in a day. The mixture may last up to about 2 hours depending on the weather. You can add extra water if necessary.
Remember also that you will have to texture the wall about 4 hours after application - time it so you don't have to get up in the middle of the night!
If you have a large expanse of wall and a couple of pals to help, it is so much easier if you use a cement mixer but make sure you have enough hands to use the mortar up before it dries out.
Applying the mortar
Applying the mortar to the walls
- Make sure the walls are damp by spraying them with water in advance and then again just before starting work. It is important that the wall is good and wet to avoid the stones sucking the water out of the mortar too quickly.
- Soak small stones or pieces of roof tile used to fill gaps in a bucket of water.
- Scoop up mortar onto a large trowel and then push it off the trowel and onto the wall with a small trowel. Press the mortar right into the wall.
- Be generous. If you put on a little too much it doesn't matter as the excess can be brushed off later.
- If you have large holes, add extra stones. Put mortar into the back of the hole, push in the stone and then fill around with mortar. If the hole is very deep, fill it in steps so the mortar has time to harden. You could fix the stone in one day and point around it the next day.
- If there are small holes the best material to fill it is old, broken clay roof tiles. They are porous.
How the professionals do it
In France the big companies mix large batches and then they have a machine that squirts the mortar out of a hose and onto the walls. The mortar still has to be pressed in and smoothed by and and the finishing also has to be done by hand. Pointing is labour intensive and expensive if you employ people to do it for you.
Applying the mortar
How to apply the mortar to the stone wall
Texturing and finishing
Brushing off the excess mortar
The mortar had been applied generously and generally flush with the face of the stones. Leave it to set. This could take about 4 hours but is dependent on the weather and temperature as well as the exact consistency of the mix. It is ready when it falls away like sand when you brush it with a wire brush. If you leave it too long you'll find it has set solid so don't forget. Do a test piece periodically until you get the right timing.
Wire brush for finishing the wall
The pointing has been applied to the wall
Brush the pointing to give texture
How to brush the pointing
A note about batches
Don't worry about leaving the wall partly pointed. Pointing is very forgiving and you won't be able to see join marks between one batch of pointing and the next lot.
I hope that this helps
I have tried to be exact and not miss out any information so if you find there are points that are not easy to understand, missing information, too much or too little information or pictures, do please leave a message in the comment box below.
This project - before ..... and after
How I learned how to point a stone wall
There is a nice little story here that I thought you might like to hear. As I said, I looked around in St Junien and Rochechouart at examples of pointing that I thought were good to get a feel for what I wanted to achieve finally. One day I was passing the Meteorite Hotel in Rochehouart which was being repointed by professionals - and, in my view, being repointed beautifully.
I went into the garden and introduced myself, said I liked their work and told them that I wanted to re-point my house. It was France and it was lunch time so nothing was going to happen until the lunch break was over. I was sat down with a glass of wine while the guys finished eating. At two o'clock when work began again, they showed me how to judge the correct consistency, how to apply it, when the mortar was dry enough to brush off and they showed me how to brush it.
Hôtel-Restaurant La Météorite in Rochechouart - beautiful pointing
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© 2016 Les Trois Chenes
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