Lime pointing Edinburgh, or lime re-pointing, is the process of removing the existing decayed mortar from between the joints and beds of the individual stone pieces. We replace the eroded mortar with new lime based mortar.
How Is Lime Pointing Carried Out?
As part of our lime pointing Edinburgh services, the old mortar is raked back (removed) to a depth of around 25mm on average. We brush and water hose out all loose material from between the stones leaving a nice firm background for the soon to be applied new lime mortar pointing.
Once the wall has dried out a bit, but is still a wee bit damp, we begin the process of pointing. Pointing is the process of replacing the mortar between the stones.
We carry this out using a pointing key and a hawk or trowel. Lime mortar is taken from the hawk using the pointing key and pressed firmly into the gaps (joints and beds) between the stones.
Once the mortar reaches the front edges of the stones (the arris) the mortar is flattened off with the pointing key to a nice finish and left to dry off for between 30 to 90 minutes – sometimes even the next day! It all depends on the conditions and required finish before moving on to the final stage.
The last step in perfect lime pointing is called the brushing up process. Depending on the desired finish we can brush over the mortar with a fairly fine paintbrush type brush which leaves a smoother finish or we can use a stiff bristled tamping brush or similar for a more rustic look.
The choice of aggregates used in the lime mortar will usually have a bearing on the type of brushing up technique used.
What Is Lime Mortar?
Lime mortar is simply a mix of sand and/or aggregate (like granite chips in the sand) and a natural lime binder. The choice of sand and aggregate is often dictated by the existing mortar if we are trying to match it.
If not, the general rule of thumb is, the bigger the joints and beds the bigger the aggregate particles. The colours of the lime mortar pointing can be adjusted by your choice of lime and sand, or more rarely, pigments can be used.
Lime is available in different strengths. The strength is indicated by a designated NHL number between 2 to 5 (5 being the most durable).
Why Should You Use Lime For Pointing And Not Cement?
Lime has been proven to be, without doubt, more effective than cement for pointing and repointing. The reasons include much increased permeability, which means it allows water to escape through the pointing and not sit behind it where it can collect and freeze in the winter.
When this happens, the pointing is pushed from the stone, breaks up and falls from the wall or building. In a situation where cement has been used and this happens, when it is forced out of the joints by frozen water, it has the habit of taking some of the stone with it.
This causes untold damage and an unsightly mess because the cement is generally harder than the stonework.
Lime pointing is a lot more flexible and is much more able to withstand movement without cracking or failing than cement pointing. So lime mortar will last much longer. It looks much better too! The bottom line: Always use lime for stone pointing. We do. The lime pointing in all the pictures on this page were carried out by us using natural lime mortars.