Many wonder, “Lime or cement mortar?” Which option is better? This is one of the common questions faced by many contractors and builders today. Generally, each mortar type has unique characteristics and properties that apply to different construction projects. Selecting the right mortar is a critical decision, ensuring the building’s long-term appearance and durability.
Both are ideal materials in their own ways and can be used according to their suitability for different projects. Read this blog to understand lime mortar vs cement mortar and its characteristics, advantages, and applications, empowering your knowledge to decide which mortar is better.
What is Lime Mortar?
It is a type of mortar prepared with lime (hydraulic or non-hydraulic), water, and an aggregate (like sand). Compared to regular cement mortar, lime mortar is more porous, which helps to remove dampness from the wall and let it dry on the surface by evaporation. This way, any salt content in the water crystallises on the lime and saves the masonry. If movement occurs, the lime mortar is designed to crack preferentially, which is less damaging and much easier to repair than cracks in the bricks or stones themselves. Lime mortar is mainly suitable for heritage and older buildings.
There are two main types of lime mortar: hydraulic lime mortar, non-hydraulic lime mortar.
Non-Hydraulic Lime Mortar
Non-hydraulic lime mortar sets by carbonation, a process where pure lime (hydrated lime) reacts slowly with carbon dioxide in the air. This type of lime requires exposure to air to harden and cannot set underwater or in very damp conditions. It sets slowly but is highly breathable and flexible, making it ideal for soft or historic masonry. It cannot set underwater, offer lower compressive strength compared to hydraulic lime. It is best suited for internal or sheltered external use, as well as soft or historic masonry. This mortar is often used in the restoration of heritage buildings, internal plastering, and areas where flexibility and breathability are crucial.
Hydraulic Lime Mortar
Hydraulic lime mortar sets through a chemical reaction with water, known as hydrolysis. This type of lime contains naturally occurring clay impurities that enable it to set through a chemical reaction with water (hydrolysis). This mortar involves a faster setting, can be set underwater, has higher compressive strength, and is more durable in exposed or damp conditions, but is still more flexible and breathable than cement mortars. This mortar is available in different strengths (NHL 2, NHL 3.5, NHL 5), suitable for varying degrees of exposure and structural requirements. This mortar is often used in marine construction, external walls exposed to severe weather, and structural masonry requiring faster setting and durability
What is Cement Mortar?
Cement mortar is a type of homogeneous mixture made by mixing cement, sand, and water. It is the most common binding material used to bind blocks, stones or bricks together. It is the most affordable option with the best durability and strength.
In the cement mortar, all the ingredients play an important role, such as,
- Cement acts as the binding agent.
- Sand adds bulk and helps to prevent shrinkage and cracking.
- Water creates a workable consistency that can be easily applied and shaped.
Cement mortar is primarily used for construction purposes and can also be decorative, with various colours and textures available to add visual interest to a building.
Key Differences Between Lime Mortar and Cement Mortar
| Property | Lime Mortar | Cement Mortar |
| Flexibility & Movement | Lime mortar can bend and move slightly with the building, so it rarely cracks. | Cement mortar is stiff and hard, so it can crack if the building moves. |
| Breathability | Lime mortar lets moisture escape from walls, helping to keep them dry. | Cement mortar traps moisture inside walls, which can cause damp problems. |
| Strength & Durability | Lime mortar is not very strong at first, but becomes stronger over time and lasts long, especially in old buildings. | Cement mortar is very strong right away, making it good for new buildings that need to hold heavy loads. |
| Curing Time | Lime mortar takes a long time to fully harden, sometimes several weeks. | Cement mortar hardens quickly, often within a day. |
| Environmental Impact | Lime mortar is better for the environment because it produces less pollution when made. | Cement mortar is less eco-friendly because making cement releases a lot of carbon dioxide. |
| Cost | Lime mortar usually costs more at first, but it can save money over time because it lasts longer and needs fewer repairs. | Cement mortar is cheaper to buy and use, but it might need more repairs, especially in older buildings. |
Advantages of Lime Mortar
The following are the benefits of lime mortar in construction:
- Lime mortar is the best option for historic restoration because it suits the breathability and flexibility of original masonry, maintaining the integrity of heritage structures.
- To a certain extent, lime mortars have a self-healing capacity, contributing to their durability. These self-healing mortars consist of dissolving, transporting, and re-precipitating calcium compounds to heal cracks and fissures.
- The flexibility of lime mortar accommodates minor building movements, reducing the likelihood of significant cracks and damage.
- Environmentally, lime mortar is sustainable and eco-friendly, as it requires less energy to produce than cement and absorbs carbon dioxide during curing, resulting in a lower carbon footprint.
Advantages of Cement Mortar
The following are the cement mortar benefits:
- Cement mortar is widely used in modern construction due to its high compressive strength, making it ideal for load-bearing structures and foundations.
- It sets and cures rapidly, enabling faster project completion and meeting tight deadlines.
- The initial cost is generally lower compared to alternatives, as materials are widely available and easy to source.
- Cement mortar’s durability and weather resistance contribute to its popularity for new buildings and heavy-duty applications.
- It offers excellent bonding properties, ensuring stability and longevity in structural elements.
- Its versatility allows it to be used in various construction scenarios, from masonry to flooring.
Disadvantages of Lime Mortar
The following are the lime mortar problems:
- Lime mortar has a lower compressive strength than cement mortar, making it less suited for load-bearing walls in taller structures. It is not suitable for high-stress applications.
- Lime mortar has longer setting times, can delay construction progress, and is not suited for projects on a tight schedule. Plan carefully before starting construction.
- Handling lime mortar demands specific skills and experience; it may exceed your budget and is not suitable where such expertise is scarce.
- Lime mortar is sensitive to harsh weather conditions during the curing process. It can be influenced by frost or excessive rain if not adequately protected.
- Lime mortar can be less readily available than cement mortar; hence, its cost can sometimes be higher than that of cement mortar.
Disadvantages of Cement Mortar
The following are the cement mortar issues:
- Its rigidity makes it prone to cracking when subjected to building movement or thermal expansion, potentially compromising structural integrity.
- Cement mortar is less permeable than lime mortar, which can trap moisture within walls and lead to dampness or mould issues.
- It is unsuitable for historic buildings, as its hardness can damage softer, breathable masonry and disrupt the original fabric.
- The production of cement contributes significantly to carbon emissions and environmental degradation, making it less sustainable than traditional lime mortars.
Choosing the Right Mortar
Choosing the right mortar depends on the type of building and its purpose. Lime mortar is best for old or heritage buildings because it allows walls to breathe and can repair small cracks on their own. It is flexible, eco-friendly, and absorbs carbon dioxide, but it takes longer to set and needs skilled workers. Cement mortar is strong, sets quickly, and is good for new buildings and heavy loads. It is easy to find and cheaper, but it is less flexible and can trap moisture, which may cause dampness. Pick the mortar based on strength needs, time, budget, and building type.
On a final note, the applications of mortar in the construction industry are infinite. Every mortar has its own pros and cons. Lime mortar has been a renowned choice for both traditional and modern buildings due to its durability and breathability. Cement mortar is known for its quicker setting times and superior strength.
The right choice of mortar depends on your project needs, budget, and construction goals. Consulting with a professional construction company such as Brick & Bolt can help ensure an informed decision.
Hemali Patel