If you own a traditional lime mortar-built brick or stone property, there is a big chance it has suffered the effects of cement mortar pointing, Gypsum plasters and none porous renders. You may have had the so-called “damp specialists” and possibly other surveyors visit. They more than likely have suggested using things like damp injections, weather sealing products, tanking solutions, damp membranes and even more cement pointing. These are all methods which have been used for many decades to try and control the effects of water ingress into buildings. However, these materials are often inappropriate for historical structures as they can cause further damage by trapping more moisture into the walls, leading to dampness and masonry decay. In addition, they can be expensive and disruptive to install. A better approach is to understand how the building functions and identify the root cause of the problem.
A traditional building relies on capillary action and airflow to remove excess moisture from the masonry walls. This process happens within lime mortars. Portland cement was patented in 1824 by Joseph Aspdin. Cement pointing started appearing on our buildings in the early 1900s. Cement mortar was chosen due to the rapid rebuilding needed, and the lack of skilled masons left after the war. Now we are faced with a ticking time bomb, as it is often used as a cheap alternative to lime mortar, especially when carrying out repairs. Cement-based mortars are the leading causes of dampness and erosion in traditionally built properties as they do not allow the walls or floor to breathe. In severe cases, this can lead to the structural collapse of buildings. The use of cement-based mortars should be avoided where possible in traditional constructions.
Cement pointing is used to seal the joints between bricks or stones. It comes in various styles. The most common are weather-struck, recessed barrel rolled, flush, lined out and strapped on. Weather struck is a pointing style that is created by using an edge to remove the top layer of mortar at an angle between the mortar joint, allowing the rain to roll down off the exposed brickwork. Barrel rolled is a style achieved by running a curved jointing tool over the mortar joint to create a convex shape. A recessed joint is a raked back mortar joint done with a chariot and nail. This style was popular in the Victorian era as it creates an ornate finish leaving the bricks exposed. Flush pointing is achieved by simply filling the joint with mortar and then smoothing it down flush with the surface of the brickwork. Lined out is another popular style in Victorian times and involves creating thin lines of mortar in the joint using a straight edge and grooving tool. Finally, strapped-on cement pointing is made by inserting nails into the existing lime mortar and then applying cement mortar to the surface of the Masonry; It is built out in layers as it’s used. It is secured by bonding to the nails, as these nails rust and break chunks of the cement mortar and start to fall from the walls.
It is now known that cement pointing and using other non-permeable materials can cause several problems in traditional homes, including masonry erosion, efflorescence and dampness. These problems can lead to the deterioration of the fabric of the building and the loss of its historic character. Lime-based mortars should be used instead of cement-based mortars. Lime-based mortars allow the masonry to breathe, which prevents moisture from becoming trapped and leads to dampness. In addition, lime-based mortars are more flexible than cement-based mortars, which helps to prevent cracks from forming. As a result, using lime-based mortars is essential for preserving the integrity of traditional buildings.
Cement-based renders are a type of construction material used for finishing the exterior of buildings. Historically, renders were made from a mixture of lime and sand, then coated with a thin layer of lime wash. This gave the render a smooth, hard finish resistant to weathering. Modern cement-based renders are made from various materials, including Portland cement, acrylic resins, and fibreglass reinforcement. In the past, renders were made using porous materials that allowed moisture to escape. This helped to prevent damp patches from forming inside the home and erosion from occurring to the masonry behind the render. However, modern renders are often made using non-porous materials, which can trap moisture and cause these problems. For this reason, it is essential
We remove render from traditional homes following heritage guidelines. this means we only use power tools where necessary taking the utmost care when doing so; our masonry skills give us the ability to remove most of the mortar from your walls with little to no damage occurring during the process. to find out more about our render removal service, please get in touch today. Our professionals have worked on some of the most historic buildings in the area and are experienced in using traditional methods to remove renderings without causing any damage. We take pride in our work and are passionate about preserving the historic environment. If you have a traditional home needing render removal, please get in touch today to learn more about our services.
Traditional Masonry Repairs
One of the most important aspects of preserving historic buildings is understanding the materials used in their construction. Modern building materials, such as portland cement, concrete and asphalt, are very different from the materials used in the past. They are much more impermeable, which means that they do not allow water to pass through them as quickly, which causes dampness to appear on the walls. When these materials are used in conjunction with older buildings, they can cause severe damage. The moisture can build up behind the modern materials and cause extensive damage to the historic structure. In addition, modern materials can accelerate historic materials’ decay rate. As a result, it is always best to avoid mixing modern impermeable materials with older buildings.
Over time we have started to see the detrimental effects cement pointing has caused on our heritage and listed buildings. Unfortunately, this knowledge doesn’t seem to filter down any further than that, so we are trying to make people aware of the materials and correct craft skills they need to have work done to their property, whether its a miner’s brick terrace house or a mill worker’s stone one, these houses still require skilled craft work and not inexperienced builders who don’t realise the damage non-porous materials will do, the more this is ignored, the more work is needed for the next repair.
Traditional Lime Mortars
Lime mortars are composed of lime and an aggregate such as sand and are used to construct buildings and structures. Lime mortar is a binding material for stone, brick, or concrete. It has been used for thousands of years and is popular today due to its versatility and affordability. One of the unique properties of lime mortar is its ability to dry out by drawing moisture to the surface and allowing its evaporation into the air. This process, known as capillary action, is driven by air movement. As a result, lime mortar is an ideal choice for buildings in humid climates or environments with a high water table. Furthermore, lime mortar is also highly porous, which allows it to “breath” and prevents the build-up of moisture within the walls of a structure. This makes it ideal for historic buildings and facilities suffering from damp and mould growth.
Traditional buildings were commonly built and maintained with Air lime mortar (Quick lime), often as a hot lime mortar. This is not an Nhl (natural hydraulic lime) which sets by relying on a hydraulic reaction; Research funded by Historic England has found these to harden beyond stated bag strength, losing porosity and capillary movement after stated setting times, meaning they start to act more like a cement mortar.
Air lime stays in a softer, more porous mortar, and the inclusion of pozzolans can give the quicklime a hydraulic set; these need to be added in the correct quantities for the required areas. Even though adding pozzolans gives a hydraulic set gauging the amount correctly, it still creates a far more porous mortar than cement which also maintains the capillary movement.
The Romans first used pozzolans in their cement, a mix of quicklime and trass (volcanic ash) with brick chippings and various grit. This cement was solid and durable, and its use spread throughout the Roman Empire. Pozzolans continued to be used in mortar and concrete throughout history, as they are a source of silica and alumina (two of the main ingredients in Portland cement). Adding pozzolans to hot lime mortar increases its hydraulic set, making it more resistant to water. However, too much pozzolan can decrease the mortar’s permeability, making it more difficult for water to pass through. Therefore, it is essential to measure the amount of pozzolan added carefully to achieve the desired results. Using pozzolans in mortar and concrete can create more robust, durable materials that will stand the test of time.
Lime plaster is also essential in traditional buildings. The lime plaster holds any excess moisture; it is drawn through the walls by capillary action, which is then drawn out through the external mortar joints by circulating air movement. It is important to remember that after applying your lime plaster, you need to apply porous paints like lime-based paint or even lime washes with pigments added; this aids in moisture transfer. Using non-permeable paint creates a barrier allowing condensation to form while trapping moisture behind it.
Excess moisture in the air can often lead to condensation, damaging buildings and their contents. To prevent this, good ventilation and air circulation are essential. This is especially true in solid wall constructions, where excess moisture can often be trapped. By ensuring that there is a flow of fresh air, you can help to prevent condensation from forming. In addition, the correct ventilation will also aid in the movement of water through capillaries. By ensuring that your building is properly ventilated, you can help to protect it from the damaging effects of condensation.
At Yorkshire Lime Company, we have a wealth of experience working with historic buildings and understand the importance of using traditional methods and materials. Our primary services include listed and traditional building consultations, mortar analysis and specifications, heritage and traditional masonry repairs, traditional brickwork, stone masonry, lime plastering, lime torching and hot lime pointing. If you want to find out more, you can contact us at 07946837106, email us at firstname.lastname@example.org or send a message here, and one of our team will be on hand to help advise. We are passionate about preserving the historic built environment, and our experienced team will be able to offer expert advice on the best way to achieve this.