Introduction
Lime, not to be mistaken for the citrus fruit, is an inorganic mineral that has been used in our built environment for centuries. It is predominantly derived from limestone or rocks containing carbonates of calcium or magnesium.
This natural material is known for its use as a binder in mortars, plasters, and renders that offer suitable exterior and interior applications. One of its main qualities is its ability to improve the breathability of walls, which goes a long way in creating comfortable and resilient building envelopes.
In this post, we will briefly touch on the history of lime, explore its production process, and also introduce you to some of the main benefits and challenges of this flexible material. Read on for the full breakdown on lime.
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Historical Use of Lime
Lime has been in use for around 12,000 years. One of the earliest known applications comes from the Natufian culture in the southern Levant, where lime plaster was used to cover burials around 10,000 BC. Much later, in a different part of the region, researchers identified Early Bronze Age pottery (circa 2950–2500 BC) coated with lime plaster.
Furthermore, at the Neolithic site of Ain Ghazal in Jordan, dozens of statues were discovered dating between approximately 6750 and 6500 BC. These life-sized figures were sculpted by applying lime plaster over core structures made of bundled reeds and grasses. Their survival over thousands of years highlights the durability of lime plaster.
It has been used as a universal material across numerous civilisations. In these, lime was used as binders in mortar and plaster to construct floors, pavements, and even waterproofing systems. For instance, for the Romans, lime-based mortar was a key material for their seminal classical constructions. They were known to add pozzolans like volcanic ash to their lime mixes in order to alter the material’s strength and load bearing capacity. The Pantheon in Rome was constructed using these techniques.
Roman architect Vitruvius, in his foundational architectural treatise De Architectura (around 25 BC), provided one of the earliest technical accounts of lime mortar. Later, the Roman naturalist Pliny the Elder described lime and sand mixtures in his Natural History (AD 77), offering further insight into Roman construction practices.
The Romans also developed large-scale lime kilns, and evidence for lime burning in Britain dates to the Roman period (AD 43–410).
After a long period with limited innovation, in 1793, British engineer John Smeaton rediscovered how to produce hydraulic lime – a lime that is set under water. He used this to rebuild the Eddystone Lighthouse in Cornwall, marking a major advancement in the scientific understanding and practical use of lime in construction. Shortly after, in 1796, James Parker patented ‘Roman cement’, a fast-setting natural hydraulic cement made by calcining and grinding septarian nodules (clay-rich limestone concretions). It was widely used in early 19th-century construction.
Between 1817 and 1818, French engineer Louis Vicat formulated artificial hydraulic lime by combining limestone with clay, laying the groundwork for the development of modern cements. A few years later, in 1824, English bricklayer Joseph Aspdin patented ‘Portland cement’, which he produced by burning a carefully measured mix of chalk and clay. While revolutionary, Portland cement was not widely used until decades later.
In 1898, the rotary kiln enabled the mass production of Portland cement, accelerating its dominance. By the early 20th century, Portland cement had largely replaced lime in mainstream construction. Lime use declined further between 1920 and 1945, especially during post-war rebuilding, as modern materials and industrial methods became dominant.
Despite this industrial shift, lime remained vital in many traditional and heritage applications. In recognition of this, the European pre-standard ENV 459 for building limes was drafted in 1995 to standardise their quality and use. This later became EN 459, which was adopted as British Standard BS EN 459, and remains the benchmark for classifying and testing building limes in Europe and the UK.
Today, lime is experiencing a revival, driven by sustainable motivations.
Processing Lime
Industrial lime begins its journey as limestone, which is extracted from quarries. Limestone is a sedimentary rock found in nature that is primarily composed of calcium carbonate. It can also be derived from other rocks containing carbonates, but limestone is the most significant source.
The quarried limestone or calcium carbonate is then crushed in a crusher. To achieve the required size the limestone may be crushed more than once. Once crushed it is screened to be sorted out into different sizes and even powder form. It is then washed to remove any impurities.
The next step is calcination, which involves burning the crushed limestone at high temperatures of around 900°C in a kiln. A significant amount of heat is required during this process to drive the chemical reaction and produce a high-quality product. The heat causes the calcium carbonate to break down and release carbon dioxide, leaving behind calcium oxide or quicklime. It is also known as burnt or unslaked lime.
Quicklime is the most volatile and reactive form of lime. As soon as it is produced, it begins to interact with the moisture and carbon dioxide in the air and hardens up. This is why it is often further crushed before being used.
To make the quicklime stable and usable, water is added to it in a process called slaking. This creates a chemical reaction which results in the production of calcium hydroxide which is slaked lime and also the release of heat.
There are three main types of slaking to keep it in different forms:
- Dry slaking – where a small amount of water is added to the quicklime to hydrate it and retain its powder form. This is called hydrated lime.
- Wet slaking – when excess water is used to hydrate the quicklime and create lime putty.
- Sand slaking – when quicklime is mixed directly with sand and water to form lime mortar.
Following slaking lime slowly reacts with the carbon dioxide in the air in a process called carbonation. During this, the slaked lime converts back to calcium carbonate and completes what is known as the lime cycle.
Types of Lime
Pure lime also known as non-hydraulic lime or air lime is derived from limestone with minimal impurities. It slakes quickly with water, sets only by reacting to the carbon dioxide in air, and is highly workable.
Semi hydraulic lime is produced from limestone containing a certain percentage of clay or other minerals. It sets partly in air and partly in water. It has a faster setting time and greater strength than pure lime but is less reactive than fully hydraulic lime.
Natural Hydraulic Lime (NHL) comes from limestone that naturally contains a higher clay or silica content. These extra minerals form compounds with the limestone and are set by a chemical reaction with water and can harden even in wet conditions. Thus, making this suitable for foundations, damp environments, and underwater construction. It is available in grades:
- NHL 2: feebly hydraulic, slower setting, less strong
- NHL 3.5: moderately hydraulic, medium setting, good strength
- NHL 5: eminently hydraulic, faster setting, strongest
Formulated lime is less commonly used in construction. It involves the addition of cementitious materials or pozzolans (like brick dust or ash) to non-hydraulic lime or Natural Hydraulic Lime (NHL) to create or enhance hydraulic properties. These additives react with the lime and help speed up the setting process.
Hydraulic lime is a general term for any lime, be it natural or formulated that sets by reacting with water.
Different Lime Products
Lime has multiple uses across a number of industries including chemical, industrial, environmental and construction. For the following purposes:
- Animal feed additives
- Asphalt fillers and hot mix stabilisers
- Adhesives (construction binders)
- Baking powder
- Battery production
- Biodiesel production catalysts
- Cement manufacturing
- Ceramic products (kiln linings, clay modifiers)
- Chemical manufacturing (neutralising agent, pH control)
- Cosmetics
- Desiccant lime (moisture control)
- Fertilisers (powder, pellets)
- Fireproofing coatings
- Flour treatment
- Preservatives
- Gas purifiers (biogas, flue gas scrubbing)
- Gelatin production
- Glass manufacturing (soda-lime glass)
- Insulation renders
- Leather processing
- Mining reagents
- Odour control (composting, livestock sanitation)
- Paints (filler and pH stabiliser)
- Paper and pulp processing
- Petrochemical processing
- Pharmaceuticals (calcium supplements)
- Pickling and food-grade pH control
- Plasters
- Plastic and polymer fillers
- Road construction (soil stabilisation)
- Steel and metallurgy flux
- Sugar refining
- Synthetic rubber manufacturing
- Textile processing (scouring, bleaching aid)
- Water and wastewater treatment chemicals
Types of Lime Products in Construction
In terms of the construction industry, lime has been used mostly as binders and surface finishes but the different types of lime available today have found use from foundations to the stabilisation of soils.
Lime products adhere well to a range of substrates including masonry, timber laths and even natural insulation materials. They also combine well with both man-made and natural materials which makes them suitable for both traditional and modern building practices.
Since lime is alkaline and caustic it is prone to causing skin irritation or damage on contact. Therefore, it is crucial that sufficient Personal Protective Equipment (PPE) is worn at all times when working with it. Manufacturer guidance also needs to be followed closely.
Cement, Concrete, Limecrete, Hempcrete, Strawcrete
Portland cement is a manufactured product that contains limestone, clay, and other minerals. These ingredients are mixed together and heated in a kiln at high temperatures. During this process, the limestone breaks down into quicklime which then reacts with the other materials to produce clinker. These are hard nodules that are then ground to form a powder to make Portland cement.
To create concrete water and other aggregates like sand and gravel are added to the Portland cement, which is the building material we all know.
In place of these Portland cement, natural hydraulic lime can be used as a binder to produce a more breathable result known as limecrete.
Going a step further, natural plant matter like hemp shivs or straw can be used to replace traditional aggregates to create hempcrete and strawcrete. These bio-based materials are breathable and insulating, making them ideal for environmentally conscious construction.
It is important to note that although most recipes for limecrete, hempcrete, and strawcrete use only lime-based binders, some commercial products may include a small amount of cement to accelerate curing or add strength. Therefore, if you are aiming for fully breathable and low-carbon results, make sure you check with your supplier.
Hydrated Lime
Hydrated lime is a dry, powdered form of slaked lime which is commonly sold in bags for use in construction. It is added to mortars, plasters, and renders to improve their workability and water retention.
Lime Mortar
Lime mortar is a traditional binding material used to hold masonry elements like bricks or stones together or for repointing. It is usually a mix of either hydraulic or non-hydraulic lime, aggregates typically sand, and water.
Unlike cement mortar, it is flexible, self-healing, and vapor permeable which allows for the construction of breathable structures that can accommodate movement with minimal cracking.
In terms of application, for bedding, mortar is spread with a trowel and bricks or stones are laid into it and the excess is removed.
For repointing, first the old mortar is raked out and the joints are dampened. Then new mortar is pressed in firmly by hand or with tools. The repointed areas can be finished with a brush or a pointing iron once the mortar is thumb-firm.
Lime mortar must be kept moist for it to carbonate and set properly. It should also be protected from drying too quickly and from exposure to frost or heavy rain.
Lime Grout
This uses lime as a binder and much like normal grout this is used to fill voids in stone or brickwork. It can be made from lime putty (non-hydraulic lime) or hydraulic lime. Lime grout is commonly used in restoration and conservation work.
Lime Screed
A lime screed is a breathable floor layer that is composed of lime, mostly natural hydraulic lime (NHL) and aggregates. They serve the same purpose as concrete-based screeds.
Lime Plaster
Lime plaster is a traditional internal wall and ceiling finish made using lime and fine aggregates like sand. It provides a smooth, breathable surface that regulates indoor humidity and reduces the risk of surface condensation. It works well on most substrates like lath, masonry, and natural insulation materials.
There are also specialised types of lime plaster:
- Insulating lime plaster, which incorporates lightweight aggregates like cork or hemp shiv for added thermal performance.
- Levelling or base plasters, which often include fibres (typically animal hair, though natural plant fibres may also be used) to improve tensile strength and reduce cracking.
Lime plaster must be applied correctly in order to perform well. Before application, substrates need to be cleaned off any loose dust or debris and dampened thoroughly.
For internal walls and ceilings lime plaster can be applied in a traditional three-coat system:
- Scratch coat – A base coat that is applied to provide a key for the next layer. It is often scored or scratched while it is still wet.
- Float coat – The second coat is used to level and build up the surface. It is lightly textured.
- Finish coat – A fine topcoat is applied to get either a textured or a polished finish, ready for limewash or paint to be applied on top.
Lime plaster can be applied by hand using trowels which is the most common method of application. Otherwise, it can be sprayed directly onto the surfaces. Each layer must be allowed to begin setting before the next is applied.
In modern applications, especially when lime plaster is applied on top of natural insulation boards, a reinforcing mesh is embedded in between the scratch and float coat. This is done to control movement and minimise the risk of cracking.
Curing is critical and may take several weeks. The plaster must be kept damp and protected from direct sun, wind, and frost to ensure proper carbonation. Lime plaster also requires routine maintenance over its lifespan.
Lime Render
Lime render is a breathable external wall coating made from a mixture of lime, sand, and water. It is applied to protect building facades from the weather while allowing trapped moisture from within the wall to escape. This further helps in reducing dampness and preventing structural decay.
For the application, the substrate preparation is similar to that of lime plaster. Lime render is typically applied in two or three coats, depending on exposure. Like plaster, it begins with a scratch coat, which is sometimes thrown or ‘harled’ on. This may be followed by a float coat, and then a thicker single finish coat to withstand weathering.
The overall application process is very similar to lime plaster. However, lime render is designed to be more robust and textured to handle external conditions.
Limewash
Limewash, also known as whitewash, is a traditional breathable wall finish made from lime (mostly hydrated lime or lime putty) and water. It can be applied to both internal and external walls for its natural finish and antibacterial qualities.
Lime Paints
Lime-based paints are similar to limewash but often include additives like casein or cellulose to increase durability and ease of application. They provide vapor-permeable and matte finishes that can be applied both internally and externally atop breathable lime plaster or render.
Lime Putty
Lime putty is a thick paste made by slaking quicklime with water. After slaking, the putty is often stored and aged in airtight containers to improve its quality. Doing this improves plasticity and adhesion which is essential in restoration work. It is used for making mortars, grouts, and fine plasters.
Limewater
This is a diluted solution of slaked lime in water. It is used for curing lime plasters and limewashes.
Milk of Lime
Milk of lime is a thinner suspension of fine lime particles in water. It is often used for specialist coatings and treatments.
Lime Manufacturer Systems
Lime-based products are often available as part of complete systems provided by manufacturers and suppliers. These systems typically showcase compatible components, such as insulation, lime renders, and finishing plasters. They also provide detailed application guidance to ensure proper performance and long-term durability.
The following section presents a series of illustrated wall build-ups that demonstrate how lime products and natural insulation materials can be integrated into construction. These examples are inspired by existing manufacturer systems and highlight common approaches to using lime in both retrofit and new build contexts.
The first example is of a retrofit external masonry wall below utilises natural and breathable materials. It can also be applied on a solid stone wall.
We have drawn inspiration from the following:
A similar retrofit system can be applied internally as shown below. The only difference here is that wood fibre insulation boards are used instead of expanded cork insulation boards, to show you different material options.
The systems we referred to include:
- Ecological Building Systems – Retro Eco Wall
- Ty-Mawr Lime – Internal Wall Schneider Woodfibre Insulation System
- Lime Green – Warmshell Internal Insulation
It is also key to ensure that the external face of the wall is in good condition and protected from moisture before this type of internal system is applied. You will find more details on this from the manufacturer websites mentioned.
The following illustration is of a special retrofit external wall system that addresses both splashback from rainwater and salt contamination. This approach is particularly useful for solid masonry walls exposed to rising damp or driving rain. This system is also suitable in cases where space is limited, and internal insulation may not be practical.
We have referred to information from Ecological Building Systems – Diasen Diathonite range.
This illustration shows a breathable timber frame wall system suitable for new builds. It combines natural insulation materials with lime-based finishes to create a vapor-permeable wall build up.
It is inspired by the Ty-Mawr Lime – Timber Clad Timber Frame System.
Benefits of using Lime
The use of lime products in construction brings about a great deal of advantages:
Breathable
Lime is highly vapour-permeable which means it helps keep the building dry by allowing moisture to escape, rather than trapping it. This helps the building breathe and works to reduce the risk of damp, mould, and structural decay. It is also able to create a comfortable indoor environment by regulating humidity as it absorbs and releases moisture effectively.
Workability
It is an excellent binder known for its workability. Lime-based products can be easily shaped, spread, and finished using hand tools or spray application. They adhere well to a wide range of substrates.
Durable
Lime forms a long-lasting, resilient surface that can withstand the test of weather and time. It also possesses self-healing properties which can prolong the life of masonry. Lime is also a non-combustible material.
Sustainable
It has lower embodied energy than conventional materials as it requires a lower temperature for calcination. Not only is it biodegradable at the end of its life cycle but it also acts as a carbon sink, reabsorbing carbon dioxide from air as it sets through the carbonation process. Many lime products are free from synthetic additives and are biodegradable. Some even have antibacterial properties due to their alkaline nature. But do bear in mind that not all lime products are cement free, so check with your suppliers if you are aiming for a fully natural solution.
Versatile
Since lime can be mixed with other aggregates, they create robust products that can be used for a variety of applications and can stand the test of time. Some lime plasters even incorporate insulating materials that can work to improve the building’s thermal performance. Most of all it pairs well with historic materials in conservation contexts.
Flexible
As it is flexible it can accommodate building movement, thermal expansion, and freeze thaw cycles, with reduced cracking. This makes lime especially suitable for historic buildings and solid-wall construction.
Aesthetic
Lime is a tried and tested material applicable in restoration projects as well as new builds. The finishes it offers are natural, timeless, and available in different colours to suit various aesthetics.
Reversible
One of lime’s most valued qualities in conservation work is reversibility. Lime mortars and plasters can be removed with minimal damage to the underlying structure. also improves the potential for masonry reuse and recycling.
Challenges of using Lime
Despite the incredible benefits, there are considerable challenges when using lime products:
Production Inconsistencies
Limestone from the same deposit can contain different compositions of carbonates and other minerals. These variations can affect the performance of the lime produced, making quality control a key concern. To address this, manufacturers set out certain parameters for their products. You will benefit from familiarising yourself with these if you are looking for a specific material output.
Handling Risks
It is important to handle quicklime safely. As it is highly alkaline when wet it involves risks like chemical skin burns. Therefore, proper personal protective equipment (PPE) needs to be worn, and neutralising agents need to be on hand in case of accidental contact. A well-ventilated area is also required when working with lime. Lime also needs to be sealed and stored in a dry place away from other substances to avoid contamination.
Cracking
The enhanced strength of hydraulic lime can, in some cases, create tension in historic masonry if it becomes too rigid relative to the surrounding materials. Natural hydraulic lime (NHL) mortars may also leach salts or cause staining on heritage stonework, which can be stubborn to clean and may cause long-term damage. This is why selecting the appropriate lime type and matching its strength to the substrate is essential.
Curing and Maintenance
Both hydraulic and non-hydraulic limes require longer curing times. To avoid rapid drying or shrinkage the surfaces need to be kept moist and sheltered from the elements using hessian, misting or protective sheeting. The slow curing process can take days to weeks, depending on the lime type and conditions. You will need to account for this as it will have an impact on overall project duration. Lime surfaces also require periodic maintenance like limewashing or patching.
Application Issues
Incorrect mixing, application thickness, or not waiting long enough between coats may lead to the product separating from the application surface or not bonding properly. This is why proper application procedures must be followed to avoid failures.
Moisture Damage
Hydraulic lime mortars may trap moisture within walls if used in thick coats or with dense aggregates that slow vapour transfer. This can then further lead to damp issues or even give rise to mould growth.
Unfamiliarity and Cost
Although lime has been in use for many years, it is a specialist craft. This means very few craftsmen are skilled in working with lime. As a result, labour costs may be higher due to the need for trained professionals. However, new manufacturers are working to bridge this gap and formulate lime products that are more accessible to modern contractors.
Here are some recommendations for some lime related further reading for you:
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Conclusion
Lime-based products continue to play a vital role in modern construction, offering sustainable, breathable, and long-lasting solutions for both new builds and historic restorations. Their natural composition and proven performance make them a reliable choice if you are seeking healthier buildings and environmentally responsible materials.
We hope this post was able to introduce some helpful and digestible information on lime as it is used in the construction industry.
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Author
Written by Valanne Fernandes, a Part 2 Architecture graduate. Valanne is a content creator with First In Architecture, spending her time researching, writing and designing inspiring new content for the website.
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