How to Repoint Brickwork with Lime Mortar: A Comprehensive Guide

Repointing brickwork is a vital aspect of maintaining the structural integrity and aesthetic appeal of your property. Over time, the mortar between bricks can deteriorate due to weathering, moisture, and age. When this happens, it’s essential to repoint the brickwork to ensure the building remains strong and secure. One of the best methods for repointing is using lime mortar, a traditional material that is more breathable and flexible compared to modern cement mortar. This guide will walk you through the process of repointing brickwork with lime mortar.

What is Repointing?

Repointing is the process of renewing the external part of mortar joints in masonry, including brick, stone, and concrete. The primary aim of repointing is to restore the structural integrity of the wall by replacing old, damaged, or deteriorated mortar with fresh material. It’s crucial to address issues like cracked or missing mortar before they lead to more significant problems such as water infiltration or reduced stability.

Why Use Lime Mortar for Repointing?

Lime mortar has been used in construction for centuries due to its durability and flexibility. Unlike modern cement-based mortar, lime mortar is more permeable, allowing moisture to evaporate from the building. This characteristic is especially important in older buildings, as it prevents trapped moisture that can damage both the masonry and the mortar itself.

Here are some key benefits of using lime mortar:

• Breathability: Lime mortar is porous, allowing moisture to escape without damaging the building’s structure.
• Flexibility: Lime mortar can expand and contract with temperature fluctuations, making it less prone to cracking.
• Environmental Friendliness: Lime mortar has a low carbon footprint, making it a sustainable choice for repointing.
• Aesthetic Compatibility: Lime mortar can blend more seamlessly with older brickwork, maintaining the character and appearance of the original building.

Tools and Materials You’ll Need

Before you start the process, ensure you have all the necessary tools and materials on hand. Here’s a list of what you’ll need:

• Lime mortar (pre-mixed or in powder form, mixed with water)
• Trowels (pointing and brick trowels)
• Wire brush or grinder
• Chisels and masonry hammer
• Mortar board or mixing tray
• Sponge
• Bucket of water
• Protective gloves and goggles
• Dust mask
• Scraper or joint raker
• Brush for cleaning the brick surface

Step-by-Step Guide to Repointing Brickwork with Lime Mortar

Step 1: Inspect the Brickwork

Before starting the repointing process, inspect the brickwork to determine the extent of the damage. Look for areas where the mortar is cracked, missing, or crumbling. Check if the bricks are loose or damaged as well. If there are any significant issues with the brick itself, it may be necessary to repair or replace the bricks before repointing.

Step 2: Clean the Joints

Use a wire brush or grinder to remove any loose mortar from the joints. If the mortar is severely eroded, you may need to use a chisel and hammer to carefully remove it. Be cautious not to damage the surrounding bricks while doing this. The goal is to clear out all old, weakened mortar to allow the new lime mortar to bond securely.

Once the joints are cleaned, use a brush to remove any debris or dust. You can also rinse the joints with water to ensure a clean surface for the new mortar.

Step 3: Prepare the Lime Mortar

Lime mortar is available in both pre-mixed and powdered forms. If you’re using powdered lime mortar, follow the manufacturer’s instructions to mix it with water. Typically, the mix ratio is about 1 part lime to 3 parts sand, but this can vary depending on the specific type of lime and sand being used.

The consistency of the lime mortar should be similar to that of peanut butter: firm but spreadable. Mix only the amount of mortar that you can use within a couple of hours, as lime mortar sets relatively quickly.

Step 4: Dampen the Wall

Before applying the lime mortar, it’s essential to dampen the brickwork slightly. Use a sponge or brush to lightly wet the surface of the joints. This will help prevent the bricks from absorbing moisture from the mortar too quickly, which could lead to poor adhesion.

Step 5: Apply the Lime Mortar

Using a pointing trowel, take a small amount of lime mortar and press it into the joints. Ensure that the mortar fills the joint completely, with no gaps. Work from the bottom up to avoid disturbing your work as you progress. You can use a scraper or joint raker to smooth out the surface of the mortar to match the profile of the original joints.

Be sure to apply the mortar in small sections, taking care not to overfill the joints. If the mortar bulges out too much, it can crack as it dries.

Step 6: Tool the Joints

After the mortar has been applied, use a pointing trowel or a special jointing tool to smooth and shape the joints. This will create a neat, uniform finish that matches the style of the original brickwork. There are several types of joint profiles, including concave, flush, and recessed, so choose the one that best suits your building’s appearance.

Tooling the joints also ensures that the mortar bonds well with the brickwork and prevents the edges from cracking as the mortar dries.

Step 7: Allow the Mortar to Set

Once you’ve finished pointing the joints, allow the lime mortar to set for a few hours. Keep the surface moist by lightly spraying it with water during this time, as lime mortar needs to cure slowly to achieve its full strength.

During the curing process, avoid exposing the mortar to direct sunlight or strong winds, as these conditions can cause the mortar to dry too quickly and crack.

Step 8: Clean the Brickwork

After the mortar has set, use a damp sponge to clean off any excess mortar from the surface of the bricks. Be gentle during this process, as you don’t want to disturb the fresh mortar in the joints. Once the surface is clean, allow the mortar to cure fully.

Step 9: Inspect and Touch Up

After the mortar has cured completely, inspect your work. If you notice any areas where the mortar has shrunk or cracked, you can apply additional lime mortar to fill in the gaps. Make sure the joints are smooth and uniform in appearance.

Conclusion

Repointing brickwork with lime mortar is an excellent way to preserve the integrity and appearance of your building. Lime mortar is a traditional material that offers numerous benefits, including breathability, flexibility, and compatibility with older masonry. While repointing can be a labor-intensive job, the results are well worth the effort.

By following these steps and using the right materials and tools, you can ensure that your brickwork remains strong, weather-resistant, and visually appealing for years to come. Whether you’re working on a historic building or a modern structure, lime mortar is an effective and sustainable solution for maintaining your masonry.