Repointing is a skilled job that is often overlooked due to the convenience of using cement-based mortars and the prevalence of using pointing guns to apply mortar. Unfortunately, this has led to many instances of poorly done repointing jobs with cement dripping down walls and chimney stacks. This article aims to provide helpful information on what repointing is, how it works, and the benefits of repointing masonry structures with the correct type of mortar.
What is repointing?
Repointing involves refilling the joints of brick and stone buildings where the mortar has weathered away or been removed, often resulting in a mix of mortar styles over time.
Filling the joints between masonry units with mortar is essential for both the aesthetics and functionality of a masonry wall. While the mortar joint serves a significant role in the wall’s appearance, it also plays a crucial role in keeping the building dry, particularly in damp countries like the United Kingdom. Pointing protects the building by providing two-fold benefits.:
- It prevents rainwater from finding its way into the wall’s core or even to the inside face of the building through the joints between the stones or bricks.
- Lime mortars allow moisture that builds up inside the wall to be drawn to the surface allowing it to evaporate when weather conditions are suitable.
Why is it important?
When rain falls on a building, some water is absorbed by the stone, brick or mortar, while the rest enters through tiny cracks between the masonry units and the mortar. To prevent this from causing damage, the moisture must be able to escape into the atmosphere once the rain has stopped.
The best way to achieve this is by allowing it to travel through porous mortar joints. If the joints cannot release the moisture, it accumulates within the bricks or stones, leading to a high risk of efflorescence or other forms of damage. Repointing affects not only the durability of the masonry but also its appearance. If done incorrectly, repointing can cause damage to your stone or brickwork, which may be impossible to fix without replacing the original fabric.
Key signs that your brickwork needs repointing or replacing
Your home’s brickwork is the most noticeable feature, but it’s easy to miss when it needs repointing. The issue could still be present even if no apparent signs of damage exist. Brickwork may appear sturdy and long-lasting but deteriorate without proper care. Here are some key indicators that your brickwork may require repointing:
- Damaged Bricks Damaged bricks on your property can have serious consequences beyond just affecting the appearance of your home. Moisture can seep in and compromise the structural integrity of the entire building. It’s essential to address any brick damage immediately to prevent further erosion.
- Unsuitable Pointing – Improperly pointed brickwork can cause damage to the wall. This is often the case when cement mortar is used instead of traditional lime mortar. Additionally, modern mortar can trap moisture, which cannot escape through the joints. This moisture would then appear on the brick surfaces and potentially freeze in colder temperatures, causing the surface to crumble.
- Efflorescence –You may have seen white deposits on brickwork without knowing what they are. These deposits are called efflorescence, forming on bricks when water with dissolved salts rises to the surface. This occurs when there is too much moisture in the masonry, causing the salts to be drawn to the surface during drying cycles. Over time, this can cause the masonry to blister.
- Damp – Have you noticed signs of dampness in your home recently? If so, it could be trapped moisture, which decaying flooring or crumbling plaster can indicate. However, it could also be “penetrating damp “, which can happen if water penetrates through the masonry walls. A common cause of penetrating damping is inadequate pointing, which can let water into the wall. If you want to prevent this from happening, repointing can be a great way to do so.
Reasons to utilise repointing
The mortar plays a vital role in constructing your home’s walls by filling the gaps between the masonry. However, the mortar may degrade over time due to weathering, and repointing becomes necessary. Repointing is carried out to maintain drip details, such as coping joints and string courses, ensuring that they effectively direct water away from the building. It also helps prevent water ingress around window sills and above lintels. Ultimately, repointing improves the overall appearance and functionality of the walls.
Protect the surface area.
It is critical to maintain the integrity of masonry, and building details are often overlooked during pointing work. To prevent significant erosion to your masonry, it is essential to regularly check if your building details are shedding water correctly. This can be achieved by ensuring that water drips away from the building and does not run straight through the joints and down your walls.
Preventing water damage
Dealing with leaking roofs and damp wall patches can be a significant hassle. However, there is a solution that can prevent these issues: repointing. The leading cause of these problems is often faulty mortar, but it’s easy to overlook this as a possible cause. Places like chimneys, ridge tiles, and roof copings are often ignored, but they are usually the first places where mortar begins to deteriorate.
Preserve the integrity of your structure.
You may already know that the weather in the U.K. can be pretty harsh. However, it’s important to note that it can also affect the quality of your home’s pointing. If this happens, repointing your masonry with a compatible mortar is recommended to maintain the integrity of your structure.
It can be pretty cost-effective.
Yes, you read that right! Repointing does not have to be extremely expensive, especially if you keep on top of any maintenance, but the price depends on the size of the area that needs repointing.
“Can I Repoint The Brickwork Myself?”
While it is technically possible to repoint your brickwork, we advise against it without the right supervision. Although the materials needed for the job are not overly costly, it can be a very time-intensive process and mixes vary depending on the type of masonry and locations, certain areas may also be challenging to access without professional equipment. For optimal results, we suggest entrusting the repointing of your brickwork to specialists like ourselves who have the necessary expertise and experience.
Mortar: Mixing, preparation and appearance
Buildings constructed before the early 20th century likely used lime-based mortar. Check for white lumps, these lumps of inadequately slaked quicklime are critical indicators that a hot lime mortar was used for building or pointing.
Something often overlooked is the sand type, its colour, and whether the aggregate is fine or coarse. This is important not only for aesthetics but also because it makes up the pore structure of the mortar, creating the capillary channels for moisture to move through.
You may also notice other additions such as coal, broken brick, or shell. These are often added as bulking agents and contribute to the mortar’s unique characteristics. This information can be used to design a new mortar that matches the existing pointing. Be careful when selecting a sample of mortar to copy to ensure it is not later inappropriate work.
When repointing masonry, choose a mortar mix that matches the porosity of the existing masonry. More porous mixtures prevent moisture from building up, which causes decay. Avoid using less porous cement-based mixes in traditional homes, as they inhibit water from evaporating through the joints trapping it into the masonry.
Lime binders are prepared differently from cement mortars to ensure a consistent mix. For example, N.H.L. is weighed into the mix following the manufacturer’s R.B.D., which varies depending on the strength and manufacturer of the chosen N.H.L. Quicklime (burnt limestone) is also weighed to achieve a consistent volume of lime for each mix. 1.1 kg of quicklime requires 1 litre of water to slake it. Lime putty is the only lime binder that isn’t weighed and is mixed by volume.
Rest assured that if you notice that the new patch of pointing seems to be brighter than the original mortar, there is no need to worry. This is a common occurrence. If you have selected the appropriate grit and binder, the weather will eventually help tone down the patch’s brightness, making it blend in more seamlessly with the surrounding area. As a result, the contrast will become less noticeable over time.
Don’t Risk Cracking
When working with Lime binders, preparing and handling them with care is crucial. Before applying the mortar, the joints between the masonry should be dampened. The mortar must be used under compression, starting from the back of the joint and building outwards.
After application, the mortar requires attention. If using N.H.L., it should be kept wet throughout the day to prevent it from drying too quickly. A churn brush should be used when the mortar is ready to compact the lime into the wall, closing any fissures caused by shrinkage. The mortar must be hydrated for at least five days to achieve the hydraulic set.
A traditional hot lime mortar, made from quicklime, follows the same application process. Still, if mixed and slaked correctly, it retains the moisture it needs to carbonate, so it requires less aftercare compared to an N.H.L.; with any lime binder, it is crucial to make sure the mortar is compacted after it has had time to remove excess moisture otherwise further shrinkage can occur.
To prevent damage to the brickwork or stones used in a wall, it’s essential to use a mortar that is not harder than the masonry. We advise against using modern cement or N.H.L. mortars with high compression strengths and instead recommend opting for a lime-based mix, which is more traditional. This will ensure the joints are porous and not impermeable after repointing the masonry.
Types of pointing styles and finishes
Various styles of pointing have been produced across the U.K. over the centuries, which is still evident in some of our heritage buildings. Depending on where you are located in the U.K., the names of these pointing styles may also differ so we will list a few of the most common pointing finishes.
The most modern finish is known as bucket handle or barrel struck. This produces a concave finish and is most common in contemporary housing.
Weather-struck is another pointing style found in modern and traditional homes. To produce a weather-struck joint with lime mortar, you would fill the joint out and compact back flush. Then, when the lime is ready, you rake the cannon back out at an angle with a straight edge, slightly revealing the underside of the masonry above, leaving an open pore structure.
Recessed pointing is a style often overlooked due to the lack of understanding. The Victorians used recessed pointing in conjunction with black coal ash mortar; this made the buildings look mortarless, leaving only the bricks visible. You would use a chariot for raking the mortar out of the brickwork with a nail gauged to depth to produce an even level throughout.
Flush pointing is another common type found on traditional buildings and is the default style for a heritage building when the existing finish can not be identified. The mortar is filled out and beaten back to produce a flush finish when enough moisture has dispersed. It is beaten back to compact it tightly into the mortar joint. This prevents further shrinkage while still leaving an open pore structure.
Tuckpointing is a technique used to fill joints in masonry, particularly brickwork, to give the impression that they are more refined and uniform. The joints are filled with mortar that is coloured to match the bricks and then scored with a narrow groove into which a thin ribbon of contrasting mortar, usually white, is pressed into the groove. Tuck pointing was commonly used on facades or embellishments between the late 17th and early 20th centuries to imitate superior “gauged work” and conceal irregular, damaged, or cheap bricks.
Other styles of traditional pointing include line struck and ruled out; these styles are produced using a straight edge like a ruler or length of wood, and tools are used such as a brick jointer or bucket handle and a pointing trowel or butter knife to produce a straight line running through the mortar.
There are many other styles of pointing in the U.K. Galleting (also known as garneting or cherry cocking) is a style of pointing that many people are unfamiliar with. This involves pushing small pebbles or pieces of slate and flint into the lime mortar before it cures. It is unclear whether galleting serves a practical, structural function or is purely aesthetic.
A few things to consider
When choosing the type of mortar you will use when repointing your masonry, three things need to be considered. They are as follows:
The Type Of Masonry to be Repointed
The less porous and denser materials can accommodate stronger mortars (e.g. hydraulic lime mortar) if the exposure of the brickwork means that extra strength is necessary. The more absorbent and softer masonry materials require a higher permeability of mortar, such as carbonating lime mortar.
The Condition Of The Masonry
If your masonry is decaying or has already decayed, then pointing may not be the only solution needed. You may need to replace the masonry or apply a render or shelter coat to protect it from the weather.
The Exposure Levels
As we have mentioned above, the exposure levels must be investigated before you decide on the type of mortar you will use to repoint the wall. You need to check a wide range of areas, including the chimney and roof parapet. This is because these areas and others with high exposure will require stronger mortars than those with less exposure to the elements.
The use of power tools
When you are removing old mortar before repointing it, you should try and stay away from using power tools such as angle grinders. This is recommended because they do not entirely remove the mortar within the joints, and you can easily damage the masonry by widening the joints, cutting into the arris of bricks, or scaring the face of the masonry. This completely changes the aesthetics of the building. Using power tools also creates a considerable amount of dust, making it difficult to track where the blade is.
However, suppose you are dealing with challenging, cement-rich mortar applied deeply into the joints. In that case, you may use a thin diamond disc cutter to carefully breach the cannon along the centre of the joints, creating a decompression line through the mortar. This will then allow you to remove the mortar with a hammer and chisel to avoid damage to the corners of the masonry. Alternatively, you could also use a masonry drill to create a line of holes along the centre of the joint, making it easier to break up the mortar.
Oscillating tools like multi-cutters are versatile and valuable devices that can accomplish various tasks, from cutting through metal pipes to sanding wood surfaces. The best part is that these tools are safer than grinders and can be used without risk of injury if safety precautions are followed. Additionally, oscillating tools are incredibly safe for heritage buildings, where preservation and protection are paramount. They’re delicate and highly customisable, allowing workers to execute the job precisely and carefully while avoiding damage to the ancient buildings’ structural integrity. Thus, multi-cutters and other oscillating tools are exceptional for those who want to approach the task safely and efficiently.
Protecting the new pointing
After completing the repointing process, it is crucial to safeguard the masonry until it can endure damage from rainfall or frost during the colder months. The length of time for protection may vary depending on weather conditions during repointing and the mortar mix used. It is recommended to protect the masonry for at least a week. However, extended protection is better in extreme weather conditions or work done during Autumn. While all mortar mixes require good aftercare, non-hydraulic lime binders need more attention during the final stages of repointing.
You can significantly reduce the need for frequent maintenance by ensuring proper protection during the repointing process. Taking necessary precautions during repointing can help you avoid the inconvenience of dealing with issues that arise from unprotected repointed walls. Properly repointed masonry can last centuries without requiring repairs, underscoring the importance of hiring a professional to do the job correctly.
Hessian can protect your completed reporting during winter months if it is fitted correctly. During summer, thick blankets (or even carpet underlay!) are brilliant at protecting your repointing because they maintain a humid environment as the mortar cures. They also absorb more water and stay damp for longer than hessians do.