How to Repoint Brickwork
How to Repoint Brickwork
Repointing brickwork is the process of refreshing the mortar joints between bricks in walls and masonry. This kind of maintenance is crucial for maintaining the structural integrity and weather resistance of a wall. Without it, your wall could be exposed to damp issues, bricks shifting, and other problems.
Crumbling mortar, loose bricks, or water ingress are all common signs which can mean that the structure needs repointing. Large or complex repointing jobs, for example, on the exterior wall of a house, should generally be left to professionals. However, you can still repoint small areas with the right tools and approach. In this guide, we’ll break down the essential steps to refresh your wall’s mortar mix and how to repoint a wall for a result that’s long-lasting and structurally solid.
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Key Takeaways
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Select a Compatible Mortar: Choose a mortar mix that is slightly weaker and more breathable than the bricks; use flexible lime mortar for historic or soft-brick properties to allow moisture evaporation, and cement-based mortar only for modern, dense masonry.
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Prioritise Joint Preparation: Rake out old mortar to a uniform depth of 15–20 mm (or twice the joint width) and clean the gaps thoroughly with a wire brush to ensure the new mixture bonds securely to the masonry.
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Manage Moisture Levels: Lightly dampen the bricks before application to prevent them from "sucking" water out of the new mortar too quickly, which causes premature drying, cracking, and a weakened bond.
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Layer and Tool Correctly: Press mortar firmly into joints in layers to eliminate air pockets, and wait until it is firm enough to hold a thumbprint before using a jointing iron to match the original profile (flushed, recessed, or weather-struck) for effective water shedding.
Signs Your Brickwork Needs Attention
Brickwork mortar often fails due to exposure to the elements over time. This process can be accelerated by the use of inappropriate materials. Over time, repeated yearly cycles of rain, frost, and heat can cause the mortar to crack and crumble, which will hurt its ability to hold bricks together and protect the wall from moisture.
Here are some common signs that brickwork might need repointing.
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Cracked or crumbling mortar – The surface of the mortar can appear broken, loose, or powdery.
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Gaps and voids appearing between bricks – Visibly missing mortar joints – are a clear indicator that moisture may be penetrating the wall.
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Step cracks – Zigzag-shaped cracks that follow the mortar joints can indicate settling and pressure, which harm the wall’s structural integrity.
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Water staining – Dark patches or white, powdery deposits on brick surfaces are a sign that moisture is passing through deteriorated mortar.
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Mortar softness – When gently testing the mortar with a mortar rake, if it easily falls away or disintegrates, this is a clear sign of failure.
Choosing the Right Mortar Mix for Repointing Brick
Matching the new repointing mortar mix to the existing brickwork’s permeability and strength is essential, as mortar and brickwork work together as one system. The mortar needs to be slightly weaker and more permeable than the bricks it’s bonding to. This allows moisture to evaporate through the joints rather than getting trapped in the masonry and causing damage.
If an incompatible mortar is used instead of a more breathable, lime-based mortar, it can speed up the process of deterioration of the brickwork itself. Inappropriate mortar will not only undermine a wall’s ability to “breathe” but can also transfer stresses to the brick units, increasing the risk of cracking and surface damage. Here are some key considerations when choosing your mortar mix.
Brick type and age – Older bricks that are fired at lower temperatures, or reclaimed soft clay bricks, often require lime-rich and breathable mortars. These mortars are better at accommodating movement, whereas more modern, dense bricks can accept stronger mixes.
Exposure to weather – If you’re in an area with driving rain, frost, or coastal salt spray, it’s important to choose repointing mortar that can escape and absorb movement without cracking.
Structural requirements - Load-bearing walls or areas under stress will need a more balanced mortar that supports compressive forces. It’s also crucial to use a quality plastering hawk, bricklaying trowels, and other tools to form well-compacted and correctly tooled joints.
Traditional Lime Mortar vs. Modern Cement Mortar
Lime and cement mortar behave very differently due to their basic properties. Choosing the correct one depends on the materials and age of the wall you’re brick pointing. Lime mortar is a more flexible and breathable mix. Cement mortar, on the other hand, is stronger and more rigid with high compressive strength.
When each option is appropriate:
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Lime – Best for historic buildings, period properties, and any structures built with soft, porous bricks or stone, where breathability and material compatibility are important for long-term preservation.
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Cement - More suited to modern structures that use harder, dense bricks or concrete blocks, where load-bearing performance is a priority and controlled moisture movement is less of a concern. It also provides a strong base for modern masonry fillers used for repairs.
Understanding Mortar Types: N, O, S, and M
Types N, O, S, and M are different types of mortars classified by their compressive strength. It’s important to use mortar that’s weaker or more flexible than the masonry you’re working with to prevent trapping moisture or cracking units. Here’s a comparison table showing where each type is better suited.
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Mortar |
Suitability |
Repointing Guidance |
|
Type M |
Heavy, load-bearing walls, retaining walls, and foundations. |
Too strong and rigid for most brick pointing jobs. Can trap moisture and damage softer masonry. |
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Type S |
Strong mortar for footings, below-grade walls, and some structural work. |
Can be used for repointing with caution. Often too strong for older masonry except in specific conditions. |
|
Type N |
Balanced strength and workability, good for general above-grade walls, chimneys, and veneers. |
A common choice for brick pointing is where moderate strength and flexibility help accommodate movement. The lime content improves moisture handling. |
|
Type O |
Low strength and very workable, suitable for interior non-loadbearing walls and soft brick or stone. |
Well-suited for pointing soft or historic masonry due to high lime content and breathability. |
How to Repoint a Wall: Step-by-step
Repointing brick with the correct technique is crucial to ensure long-lasting protection and structural stability for your brickwork. Careful preparation, compatible materials, and the correct application methods are all important for a durable and weather-resistant finish. This step-by-step guide will explain how to repoint a wall for the best results possible.
What tools do you need?
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Mortar rake or an angle grinder with a raking blade
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Plugging a chisel and a club hammer
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Soft hand brush
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Jointing irons (various profiles)
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Mortar mixing equipment (bucket or mixer)
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Spray bottle or hose for dampening
Step 1. Rake out old mortar to uniform depth
Start by using a hammer and plugging chisel or a mortar rake to clear away deteriorated mortar to a uniform depth of about 15-20mm, or twice the width of the joint. Angle grinders fitted with a raking blade can also be used to speed up the process.
Step 2. Clean joints thoroughly
Once you’ve raked out the joints, brush them with a wire brush to clear away any loose debris. If there are any particles remaining, it can prevent proper bonding. Always ensure the joints are completely clean and free of clinging fragments before you proceed with adding new mortar.
Step 3. Dampen brickwork
Next, lightly dampen the brickwork using clean water. Dry bricks can rapidly absorb moisture from new mortar, which may cause it to dry too quickly and weaken. A slight dampening will slow this process, allowing the mortar to fully cure and develop its strength.
Step 4. Apply new mortar in layers
Using a plastering hawk and pointing trowel, press the mortar firmly into the joint, filling it from the back. If the joint is particularly deep, it’s best to build up mortar in layers, compacting each layer with your trowel to get rid of air pockets. This compression will help ensure weather resistance and structural soundness.
Step 5. Finish joints appropriately
Once the mortar is firm enough to retain a thumbprint, the final step is to tool the joints with a jointing iron so that it matches the original profile (e.g. flushed, recessed, or weather-struck). Correct finishing will help compact the surface and shed rainwater effectively, protecting the wall from water ingress or frost damage.
Special Considerations for Older and Listed Buildings
Repointing brick on older buildings calls for a much more sensitive approach compared to modern brickwork. Inappropriate materials like strong cement mortars may trap moisture and speed up decay for historic masonry. Here are some of the key considerations you’ll need to follow when repointing brickwork on older or listed buildings.
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Obtain necessary permissions – Work on listed buildings requires Listed Building Consent from your local planning authority before you start pointing brickwork.
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Match the original mortar composition – Analyse the existing mortar to make sure your repointing mortar replicates its strength, colour, and permeability.
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Use traditional techniques and materials - Lime mortar is typically required for pre-1919 properties to maintain breathability.
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Avoid mechanical damage - Hand tools are better than mechanical grinders for protecting soft, historic bricks.
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Respect original joint profiles – When pointing brickwork, make sure the work maintains the historic appearance and weathering performance of the wall you’re working on.
Things to Consider When Repointing Brickwork
Safety – Wear suitable PPE, including eye protection, gloves, and a dust mask. Ensure your scaffolding is stable and erected according to guidance from the HSE.
Cost – Account for the mortar materials, specialist tools, and access equipment. Though quality repointing requires some up-front investment, it will also help prevent expensive structural repairs further down the line.
Duration – Estimate the project length based on the wall size, mortar hardness, access requirements, and weather conditions.
Professional support – For large-scale, structurally significant, or heritage-sensitive projects, you may need to hire a professional bricklayer or conservation specialist.
How to Repoint Brickwork - FAQs
Here are some answers to common questions you can use for quick reference when repointing your brickwork.