Our house is completely made from stone, which we love. When we bought it, the majority of the walls were still the original exposed stone, however there had been some dividing walls put up made of brick. The previous owners had also put plasterboard up on some of the walls also. We decided to keep a selection of walls exposed, whilst insulating and putting up plasterboard on others. We felt this was a great balance of mixing the new and old, with white walls brightening up the space whilst still keeping the original feel with the stone.
The stone walls that we wanted to keep exposed however needed a lot of work. The original lime mortar between the stones is very old and crumbly, with cracks and parts missing in places. We knew it would need to be re-done if we wanted to keep the stone walls exposed.
This process of removing old lime mortar, and replacing with new lime mortar, is called re-pointing. It is fairly labour intensive work but it is well worth the effort for the final result.
Why lime mortar?
Lime mortar was the obvious choice for us to re-point with for so many reasons. It consists of just lime, sand and water. Lime mortar is the original building material for these stone buildings, and for good reason. It allows the stone walls to breathe, allowing moisture to escape so you do not get issues with damp.
We also love lime as it’s an eco-friendly building material!
- Lime is a natural material and doesn’t leach damaging chemicals
- It requires less energy to produce over cement
- As the lime mortar hardens it is able to reabsorb the carbon dioxide it released during manufacture making it a carbon neutral building material
- It can be produced locally on a small scale, cutting pollution and limiting transport distances
- Lime is also biodegradable and recyclable
The process of re-pointing with lime mortar
1. Removing the old lime mortar
The first step is to remove the old lime mortar. We used a mortar rake attached to a grinder to dig out about 2cm/1 inch deep, that’s was all we personally needed to do on our walls. You can also do it manually, but considering the amount we needed to do, we chose to use an electric tool. We were comfortable using an electric tool because our stones were really solid, we didn’t have any issues with unstable walls or loose stones.
2. Cleaning up the stones
After the majority of the lime mortar had been dug out, it was time to clean up the stones. Using a wire brush, we manually rubbed down the rock faces to remove any small parts of lime mortar that was not removed by the mortar rake. This cleaned the stones up lovely.
3. Making the new mix
We then mixed up the fresh lime mortar mix. You have to be careful with lime as it is dangerous to breathe in (when it is in powder form) and can give chemical burns when in contact with the skin. When working with lime we wore masks and thick waterproof gloves to protect ourselves. Once dry however the lime is not harmful.
4. Applying the mortar
We found it easier to apply the fresh lime mortar to the wall using our hands instead of tools. After filling a gap with mortar we would use our fingers to smooth it off around the stones. Any excess that fell on the floor we re-used so nothing went to waste.
5. Finishing touches
At the end of a day of applying fresh mortar, it is time to brush off the excess mortar from the rock faces. We used a wire brush to remove this, with a sweeping brush helping clean up the wall. Doing this at the end of the day meant that the lime mortar had dried enough to be brushed off, but not completely dry that it would be labour intensive.
That is all that is involved in the process! Give the lime mortar a few days to fully dry, and it’s done. There is no ongoing maintenance or any work that needs to be done, until it needs re-pointing again. And that won’t be for another 50 years or so!