Lime has a long history of being used in the construction and repair of historic buildings. 6000 years to be precise when in 4000BC, the Egyptians used lime to plaster the Pyramids.
Fast forward to 126 when the Romans used lime to build highly complicated structures such as The Pantheon. Not to be outdone, various ancient Chinese Dynasties built, re-built and extended the Great Wall of China over a period of 2000 years. And, in 1078 lime mortar was used to build The White Tower (of London); one of many English castles to be built using this versatile material.
So, it’s safe to say that lime is one of the great survivors, weathering the effects of corrosion and natural disasters for thousands of years.
Why lime? Why not?
The architects and builders of yesteryear understood the many unique benefits that lime offers, although then they perhaps didn’t appreciate the importance that many of these properties would have in today’s built environment, where sustainability and environmental issues are key agenda.
1500 million tonnes of Portland cement is manufactured worldwide each year which releases an equivalent amount of carbon dioxide into the atmosphere. It is widely reported that cement production contributes up to 10% of global CO2 emissions. Lime produces around 19kg of CO2 per tonne, compared with 175kg per tonne for cement-based mortar. So, with up to 50% less embodied energy, the use of lime mortars would make a significant reduction in greenhouse gas emissions. During the carbonisation process, lime mortar will re-absorb 13kg of CO2 per tonne, compared to cement which only manages 50% of this at 6.5kg per tonne. NB. If a traditional air lime mortar is used, in its manufacture, 100% of CO2 is absorbed.
From initial production to completed project, lime-based mortar will produce 5.5kg of CO2 per tonne, compared to cement producing a huge 165kg per tonne.
Lime is highly versatile and can be used in buildings in many different ways. Mix lime putty with sand to form a lime mortar which can be used for bedding masonry, pointing, rendering and plastering. Where fine joints are present – in ashlar masonry for example – or in gauged brickwork, pure lime putty can be used. Dilute with water and you have a lime wash for both internal and external walls; and if a coloured wash is required, pigment can be added. To make mortar repairs in damaged stonework, lime putty can be mixed with certain aggregates. Lime is also valuable in specialist stone cleaning and conservation techniques.
Lime – protecting the future – the preferred choice for eco-builders
Lime offers huge environmental benefits:
- It is a natural material
- It has low embodied energy
- It re-absorbs CO2 during carbonation
- There is no efflorescence due to high presence of sulphate-resistant binders
- Is 100% recyclable after use
- Lime is the perfect partner for low-energy, sustainable materials such as water reeds, straw, coppiced timber, earth and clay.
Buildings need to breath, and one of the key attributes of lime is that it allows a building to breathe and move. Lime allows good vapour permeability by facilitating moisture movement through the building and assisting in the drying out process. The open pore structure of lime promotes the free flow of moisture in and out of a building, thereby preventing damp, green mould and moisture build up in the cavities.
It also allows for movement within a building – again a completely natural requirement – without the need to use expansion joints. This natural movement prevents cracking, corrosion and ultimate breakdown that would occur with manufactured materials such as cement and concrete.
When appearance matters.
The use of lime mortar in both historic and contemporary buildings adds significantly to the aesthetic; it has a highly natural, organic appearance and these aesthetic qualities are hard to equal with manufactured building materials.
In historic building and conservation projects, a time-weathered appearance is key to preserving the look and feel of the period and lime is probably unrivalled in this respect. Today in contemporary building design unusual brick colours are increasingly specified; sometimes with architectural detail requiring a matching or complementary mortar. By using modern technology, it is now possible to provide precisely colour-matched mortars, which adds an extra aesthetic dimension.
EcoRight – a leading manufacturer of lime mortar, render and plasters.
EcoRight is one of the leading experts in the use of lime and lime-based products and manufacturers a wide range of lime building materials which can be supplied direct to site in silo, bags or pallets.
RIBA-approved CPD sessions are available to Architects on request, including Lime in Construction Today, Lime Renders and Lime in Building Conservation.
Contractor ToolBox Talks can be booked to help tradespeople get the best out of lime..