Specialist heritage mortar? Or just what they used for thousands of years before cement?
What is lime mortar?
Lime mortar is a type of mortar made from hydrated lime, sand, and water, and is commonly used for building and restoration work. Pointing is the process of filling the joints between bricks, stones, or other masonry elements to protect the structure and enhance its appearance. Lime mortar is preferred for pointing work in older buildings as it is more flexible and breathable than cement-based mortar, allowing the structure to move and breathe over time. This helps to prevent cracking and damage to the masonry.
Why is lime mortar no longer used in modern construction?
With the introduction of Portland cement during the 19th century, the use of lime mortar in new constructions gradually declined. This was largely due to the ease of use of Portland cement, its quick setting, and high compressive strength.
Why use lime mortar?
Lime mortar is used for building and restoration work because of its unique properties and benefits. Some of the main reasons for using lime mortar include:
- Flexibility: Lime mortar is more flexible than cement-based mortar, allowing the structure to move and breathe over time without cracking. This helps to preserve the integrity of the masonry.
- Breathability: Lime mortar is highly porous and allows moisture to evaporate from the structure, preventing dampness and promoting long-term durability.
- Compatibility: Lime mortar is compatible with traditional building materials such as brick and stone, and is often used in the restoration of older buildings.
- Workability: Lime mortar is easy to work with, making it ideal for intricate or detailed masonry work.
- Carbon footprint: Lime mortar has a lower carbon footprint than cement-based mortar, making it an environmentally friendly choice for building and restoration work.
Overall, lime mortar is an ideal choice for building and restoration work due to its flexibility, breathability, compatibility, workability, and low carbon footprint.
What are the different types of lime?
There are several different types of lime used in building and construction, including:
Hydrated Lime: Hydrated lime is made by adding water to quicklime, creating a fine powder that can be used as a mortar or plaster. It sets through a chemical reaction with carbon dioxide in the air and is known for its high strength and durability.
Fat Lime: Fat lime is a type of hydrated lime that has a higher proportion of impurities, making it less strong and more workable than standard hydrated lime. It is often used in traditional building work, where a more flexible and breathable mortar is required.
Quicklime: Quicklime is made by heating limestone to high temperatures, resulting in a dense, highly reactive substance. It is not suitable for use as a mortar or plaster but can be used as a base for other lime products, or as a building material in its own right.
Natural Hydraulic Lime (NHL): Natural hydraulic lime is a type of lime that sets through a chemical reaction with water, rather than through a reaction with carbon dioxide in the air. It is used for building and restoration work, particularly where a stronger mortar is required.
Lime Putty: Lime putty is made by slaking quicklime in water, resulting in a creamy, slow-setting product that can be used as a mortar, plaster, or paint.
Each type of lime has its own specific properties and uses, and the type of lime used in a building project will depend on the specific requirements of the project.
What is hot lime mortar?
Hot lime mortar is a type of lime mortar that is mixed and applied at a higher temperature than standard lime mortar. This process, also known as “hot mixing,” involves heating the lime, sand, and water before mixing them together. The hot mixing process results in a faster-setting, higher-strength mortar that can be used for a variety of building and restoration applications.
Hot lime mortar is commonly used in historic building restoration projects, where a high-strength mortar is required for structural stability. The hot mixing process also helps to improve the workability of the mortar, making it easier to apply and finish. However, hot lime mortar is more complex and time-consuming to mix and apply than standard lime mortar, and requires specialized equipment and techniques.
Overall, hot lime mortar can be a useful tool for building and restoration work, providing a high-strength and fast-setting solution for specific applications. However, its use should be carefully considered, as it may not be appropriate for all projects.
What is the lime cycle?
The lime cycle is the series of chemical reactions that occur when lime (calcium oxide) is produced from limestone (calcium carbonate) and then reacts with water to form hydrated lime (calcium hydroxide). The lime cycle can be summarized as follows:
- Limestone is heated to high temperatures to produce quicklime (calcium oxide).
- Quicklime is mixed with water to form slaked lime (calcium hydroxide).
- Slaked lime reacts with carbon dioxide in the air to form hydrated lime (calcium carbonate).
- Hydrated lime can be used as a building material, such as mortar or plaster, or as a soil amendment to improve soil fertility.
- Over time, hydrated lime will react with carbon dioxide in the air to re-form calcium carbonate.
The lime cycle is an important aspect of building and construction, as lime has a variety of uses and is an important material in the preservation of historic structures. The lime cycle also has important environmental and agricultural applications, as it helps to regulate the pH levels of soil and waterways, reducing soil acidity and improving soil fertility.
What are the disadvantages of using lime mortar?
There are several disadvantages of using lime mortar, including:
- Longer curing time: Lime mortar takes much longer to cure compared to modern cement-based mortars, which can result in longer construction time.
- Shrinkage: Lime mortar has a tendency to shrink as it cures, which can result in cracking and weakness in the mortar.
- Sensitivity to moisture: Lime mortar is more susceptible to moisture damage and can deteriorate more quickly in wet conditions.
- Susceptibility to freeze-thaw cycles: Lime mortar is more prone to damage from freeze-thaw cycles, which can cause cracking and other damage to the mortar.
- Higher cost: Lime mortar is generally more expensive than modern cement-based mortars, due to the higher cost of production and the specialized skills required to work with it.
- Limited availability: Lime mortar is not as widely available as cement-based mortars, so it can be more difficult to find in certain areas.
Whether or not to use lime mortar will depend on the specific requirements of your building or restoration project.
There is a wealth of knowledge online and from helpful surveyors like us. Websites such as the listed property owners club can also help find suitable tradesman for your works.
Feel free to contact us if you require any further information.