Specifier Review
Eight benefits of using lime mortar in building works

Eight benefits of using lime mortar in building works

Lime mortar is one of the world’s oldest and most durable building materials; it’s also one of the great survivors. 

Just look at the Great Wall of China where many sections were built around 518 – 618AD – by ramming earth, lime, sand and small stones between board frames, and lime has been used continuously ever since in the re-building and refurbishment for over 2000 years.  It has certainly stood the test of time.

The Romans also used lime extensively to build structurally complicated forms such as The Colosseum and The Pantheon; the latter being completed in 125AD and is one of the best-preserved architectural marvels from the ancient Roman era.  It still stands, surviving 2000 years of corrosion and natural disasters.

Let’s not forget the Egyptians who around 4000BC used lime for plastering the pyramids, recognising the durable, flexible, and breathable qualities that were desired for the construction of these superstructures.

Today lime is central to the repair and maintenance of historic, heritage and traditional buildings which demand highly flexible, breathable, and durable building materials.  But the use of lime in modern buildings is fast growing as the ecological and environmental qualities of lime is increasingly desirable and indeed, demanded in eco-focussed building projects.  Lime also offers scope for precise colour matching of brick, stone, or other adjacent materials, and can be used successfully alongside other green materials such as hemp or straw bales.

BENEFITS OF USING LIME MORTAR

1. IT’S A BREATHABLE BUILDING MATERIAL

Lime mortar is highly breathable allowing water to pass through the building thereby avoiding a build-up of moisture within the fabric and the risk of subsequent condensation or damp taking hold. The vapour permeability allows evaporation of rising and penetrating damp from within the wall. This permeability or ‘breathing’ is what helps keep the inside of the building dry without the need for a damp course or chemical treatment. The ability of lime mortar to breathe is due to the open pore structure of the material which allows a free flow of moisture in and out of the building preventing damp, green mould and moisture build up in the cavities. And, because moisture is constantly moving – rather than being of a static build up – this greatly assists in the drying out process.

Cement on the other hand is a hard, brittle material that is considerably less porous and therefore predominantly waterproof, so the use of this material effectively seals a building envelope. Cement is also much harder than soft brick or stone and this rigidity prevents necessary settling or movement of a building which will result in cracking. When cement mortar cracks, water will seep into the cracks and because of its impermeable nature, moisture won’t be able to evaporate so will be forced out through the face of the brick or stone, causing damage. In severe cases, this can result in the loss of an entire face of stone or brick. Of course, if moisture cannot escape from the envelope, it will turn inwards, resulting in damp inside the building.

All buildings are subject to weather conditions, so perceived wisdom would dictate making the building envelope watertight by applying a waterproof render. This will not have the desired effect in fact the opposite will prevail, as the levels of damp inside the building increase as moisture is unable to evaporate and moisture levels will start to build up in the wall. The ability of the materials used to lessen the ongoing impact of rain and moisture is, therefore, an important consideration for architects and specialist historic building contractors.

The health of a building’s inhabitants should not be overlooked. A breathable building is vapour-permeable, allowing moisture to escape and thus reduce the risk of respiratory ailments that could occur within a damp building.

Eight benefits of using lime mortar in building works

2. STABILISES THE INTERNAL ENVIRONMENT

It’s not just the building envelope that benefits from this multi-faceted natural material.  Because lime mortars and plasters are porous and open-textured, moisture will be absorbed and released thus stabilising the humidity within the building whilst reducing surface condensation and mould growth.

This will make for a more comfortable internal environment and reduce the risk of excessive damp that could result in respiratory issues for inhabitants. 

3. LIME MORTAR IS AN ECO-FRIENDLY BUILDING SOLUTION

Lime mortar is a truly eco-logical and environmentally friendly building material in its production, its use and afterlife.

The carbon footprint of lime production is considered carbon-neutral for a number of key reasons.

  • The raw material (limestone) is burnt at a much lower temperature in the production process than cement – 900oC as opposed to cement at 1300o
  • It therefore uses considerably less energy making it more environmentally friendly.
  • It is possible to produce lime on a small scale.
  • Extremely low energy and vulnerable materials such as earth construction and straw bales can be protected by adding small quantities of lime.
  • Carbon absorbing is achieved in the production of lime mortar. Some of the CO2 emitted during the firing process is re-absorbed by the lime as it hardens, and this continues throughout the life of the material.

Lime mortar production is also relatively sustainable, so providing no pesticides are used, it will cause no significant damage to our air quality, water supply, land, or soil.

Because lime is a natural material there is no danger of it ‘leaching’ damaging chemicals, it can therefore be safely used near watercourses without risk to wildlife or habitats. Of course, this applies equally to the use of building materials in cities and urban areas where a build-up of chemicals could be damaging to the population and where an environmentally considered material decision is required.

Lime is an excellent building solution for ecological building projects where carbon neutral or carbon negative materials are required, as it is complementary to other green materials such as hemp or straw.  Using lime with other natural materials achieves the best BREEAM rating and Code for Sustainable Homes https://www.breeam.com/ with a low embodied energy and energy performance.

At the end of life, lime mortar is completely recyclable which makes recycling bricks, stone, and other natural hard materials so much easier, as they can be disposed of as a single ‘package,’ as opposed to concrete or cement which cannot be recycled. When calculating the lifetime cost and environmental impact of a building, the amount of building waste and material destined for landfill cannot be ignored.

A further lowering of carbon footprint can be achieved by buying lime products made in the UK, thus minimising air and land miles in importation and onward transportation.  EcoRight lime products are manufactured in our own plant in Reading, Berkshire and are transported to development sites throughout the UK using the most efficient methods of transport.

4. LIME HAS GOOD ADHESION PROPERTIES

Because lime mortar is a flexible material, it will move with a building as natural thermal expansion or contraction occurs. If a hard, brittle, inflexible material such as cement is used, large cracks will develop, and the material will move away from the substrate (known as debonding) which is likely to also damage the substrate.

By incorporating lime into the mix, a gradual micro-cracking will occur. These micro-cracks are self-repairing as the lime diffuses into the minute fissures and hardens over time when reacting with atmospheric carbon dioxide – this is where lime continues to ‘take back’ the CO2 that was used in its initial production. The process is called autogenous healing.

If a substantial amount of debonding has occurred, it could be a costly exercise to remove and replace the material, but if damage is severe, then the substrate of brick or stone could also be affected to the point where a complete façade needs to be replaced.

Lime has a fine particle size (much smaller than cement) which allows for the mix to penetrate minute voids more deeply than other materials. It has gentle binding properties with good stickiness giving good adhesion to other surfaces which gives an Architect or Specialist greater scope to use other materials.

For interest, the origin of the word lime means ‘sticky material,’ so its superior bonding properties live up to the meaning of the word.

5. LIME IS PROTECTIVE

The use of lime forms a protective shield against frost and water movement due to the higher quality of bond achieved with this material and the absence of large cracks. This helps reduce the risk of water ingress.

Lime mortar also has a greater ability to transmit water vapour than cement-only mixes. This helps moisture to dissipate, thereby allowing the building to breathe and thus reducing the risk of frost damage.

In reverse weather conditions such as extreme heat, a wall will dry through natural evaporation and the effect of wind, as lime acts as a natural wick drawing water from the structure.

6. LIME IS MOULDABLE

Lime is a smooth and mouldable material, thus making it highly workable. It is much revered by craftsmen for this reason as it assists in achieving a high level of quality with good bonding ability to other materials. Tradespeople who are new to using lime sometimes fear the unknown and perceive it as a specialist or difficult material to work with. Not so, first-time users of lime-based mixes will find them a pleasure to use, and they also open up the opportunity to introduce graded and sharp aggregates into the mix which further enhance the performance and aesthetic of a piece of work.

7. LIME MORTAR IS THE ULTIMATE DURABLE BUILDING MATERIAL

The durability of lime mortar is well documented with it being a favoured material by the Chinese dynasties, the Egyptians, and ancient Romans. More recently – six hundred years ago – it was used to construct Caesar’s Tower at Warwick Castle which is another building that has stood the test of time and is testimony to this highly versatile and durable building material.

8. LIME MORTAR IS FAST BECOMING AN AESTHETIC CHOICE

Lime is just one of the most beautiful of materials and can transform even the plainest of buildings into something of beauty. Because it is entirely natural it has a soft texture with an inherent lustre that develops into a rich patina over time. The properties of lime keep a building looking good for longer. Lime mortar dissipates the salt deposits which settle on all buildings, thus reducing the potential for staining. Look at any building and you will quickly see if salt deposits are present as it appears as a chalky surface, if this is the case, chances are that lime wasn’t used and the aesthetic of the building is compromised.

Lime is used extensively in historic and heritage buildings for its natural look and ability to blend perfectly with other construction materials such as stone – St. Pancras Station, London is a fine example of this.

However, lime is now a hugely popular choice amongst Architects who are designing contemporary buildings such as The Shard where ecological solutions are sought as well as a strong aesthetic finish. Today, lime mortars can be precisely colour-matched to brick or stone which enhances the look of a contemporary build – The Tombola Building in Sunderland is a good example where the lime mortar was colour matched to the brickwork resulting in a stunning façade.

As the demand grows for ecological and environmental building solutions, lime will become a major player as one of the most ecological building materials that also has beautiful looks, high performance, and durability.

WHY CONSIDER ECORIGHT TO SUPPLY LIME MORTAR FOR YOUR NEXT BUILDING PROJECT?

  • We manufacture at our own site in Reading so can accommodate tight or lengthy build schedules.
  • We ship throughout the UK using the most efficient transport methods.
  • Available in bulk bags, full pallets, or dry silos.
  • We have lime mortar in our DNA. Our technical team has more experience working with lime than most.  There isn’t a problem we haven’t solved yet.
  • We provide x3 RIBA approved CPD presentations covering various aspects of the use of lime-based products in construction, namely:

Lime in Construction Today

Lime Renders

Lime in Building Conservation

ECORIGHT HAVE EXTENSIVE EXPERIENCE AND KNOWLEDGE OF COLLABORATING WITH ARCHITECTS AND CONSERVATION SPECIALISTS IN:

  • Historic buildings
  • Heritage buildings
  • Conservation projects
  • Ecological projects
  • Contemporary new build
  • Small development new build

ECORIGHT HAVE WORKED ON MANY PRESTIGIOUS PROJECTS SUCH AS:

Eight benefits of using lime mortar in building works

  • Wide range of colours available from natural, earth tones, greys & black & a Heritage range.
  • Colour-matching service and on-site advice if required.
  • We can provide on-site ‘toolbox talks’ for contractors, or online.

EcoRight is one of the UK’s leading manufacturers and suppliers of lime mortars, plasters and renders and is part of the Owlsworth Building group of companies which include:

Old House Store – traditional building materials

Eco House Store – ecological building products

Quatra Direct – trade building supplies

CONTACT ECORIGHT

For expert help and advice or to book an online RIBA CPD presentation or  Toolbox Talk, email Roger Shroff roger.shroff@ecoright.co.uk or telephone the technical team on 0845 873 3888.

https://www.ecoright.co.uk/

Lime mortar is highly aesthetic and can be exact colour-matched to bricks or other adjacent materials making it a good choice for conservation or new build.

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