One of the many services we provide here at JC Plastering and Lime is that of Lime Putty Repointing. We provide this, because over time, buildings (particularly older structures) are prone to wear and tear and need preservation to retain the original integrity of the structure. This is when repointing is done. When a building needs repointing, the use of lime products (in our case, lime putty) is a must-needed material used. This is because cement-based mortars are far too hard to be used in the preservation of an old structure and can damage masonry.
Lime mortar is best used in repointing as it is significantly more porous and softer than materials such as cement. This allows for moisture to evaporate from the joints more effectively, thus reducing the level of moisture in the fabric of the building. Also, it can be said to reduce the likelihood of soluble salts appearing on the surface. Over time, these salts can build up and can cause any brick work to break down.
Repointing is argued to be essential to ensure the durability of a wall. Over a period of time, weather systems such as rain or wind can weaken the lime putty between any bricks, thus allowing water into the joints and causing water damaging. Repointing as a process, involves removing any old putty in the joints of brickwork and replacing it with new lime. The process behind lime putty repointing is as followed:
- Surface preparation – it is important to prepare the surface before any kind of construction work is completed. This involves brushing out any loose material and dampening each joint, making sure to give adequate time to allow the water to soak into the joints. The mortars should be as stiff as possible to allow for the reduction of smearing or shrinkage.
- Repointing process – this involves removing the mortar joints with a rake, the depth to which you remove will depend on the width of the brickwork.
- Damping down – by dampening the mortar joints and brickwork down, it reduces the risk of the mortar from drying too quickly. If this does happen, it can cause cracking, which means the lime will not carbonate properly.
- Preparing the mortar – this can be done by a pre-mixed mortar or by traditional mortar making methods.
- Application – a small amount of mortar is placed onto a hawk and then applied to the brickwork with a pointing iron or trowel. The mortar should be at the right consistency and should be always worked in the same direction, pushing it into place as you go along. Once the mortar is applied to the wall, avoid over working it as it can weaken the material.
- Final touches – the mortar should be left for several hours to set and a scrubbing brush should be used to remove any excess mortar from the brickwork.
This is a simple guide to repointing using lime putty, however we have a more in depth page on our website if you are interested in learning more about it.