Traditional Building Renovation, Restoration & Conservation
Natural & Healthy
Contemporary & Historic
Lime
What is lime?
Limestone (calcium carbonate CaCO3), when burnt at 900°C in a kiln, loses carbon dioxide (CO2) and becomes quicklime
(calcium oxide - CaO).
On contact with water, it combines with it, producing great heat, to form slaked lime (calcium hydroxide -ca(OH2), also called
lime putty or pure lime. This gradually takes up carbon dioxide again from the air and changes back to calcium carbonate.
This ‘setting’ is called carbonation. Lime putty mixed with a sand and an aggregate makes mortar.
Pure Lime which is also known as:
Air lime, because it hardens on exposure to air
Fat lime, from its consistency in putty form
Non-hydraulic lime, it sets through air and not through water
Lime putty is deemed to be carbon neutral. It gives off CO2 during the kiln
firing process, but draws carbon dioxide in from the atmosphere on setting.
A Brief History of Lime
Thought to be amongst the first frescoes made by man, the Lascaux Caves in South-Western France are of natural iron oxide pigments applied onto damp cave walls of high calcium content (Limestone). They are believed to date back as far as 17,300 years.
For more than 7,500 years burnt lime stone has served as the principal cement (or binder) in mortar, plaster, render, and lime wash. The ancient peoples who inhabited Jericho in the Jordan Valley made a plaster from lime and unheated crushed limestone. The plaster was used to cover walls, floors, and hearths in their homes.
Dating back 6,000 years to the days of ancient Egypt they used a lime/gypsum mix to
plaster the pyramids at Giza. Ancient Grecian builders used fine lime plasters in creating the
Parthenon and Roman builders used it extensively throughout their empire in their homes
and temples.
In England, in the Medieval period most houses were timber framed and highly susceptible
to fire.
To help preserve the welfare of the city of London after fire destroyed
London Bridge in 1212, King John passed a law that all shops along the Thames should
be lime plastered and rendered and lime washed inside and out, as lime has very good
fire proofing qualities.
During the 14th century in England , artisans, using trowels, applied decorative lime plaster to the exterior of timber-framed structures. Many of these beautifully crafted and regionally diverse ancient buildings still stand today and the lime mortars, plasters and lime paints used have proven themselves as extremely durable and resilient.
Modern cement or Portland cement was developed by Joseph Aspdin, a mason/bricklayer,
in Britain
in 1824. He made it from artificial hydraulic lime similar in properties
to the material known as Roman Cement which was patented in 1796 by James Parker.
The name is derived from its similarity to Portland stone, a type of building stone
that was quarried on the Isle of Portland in Dorset.
Despite the widespread common use of lime up until the end of World War II , the popularisation of Portland cement reversed the age-old tradition of utilising natural lime mortars. As industrial progress gained steam, a population boom demanded that buildings go up cheaper and faster. With the large scale rebuilding projects during the 1950's, 60's and 70's in European cities the fate of lime was sealed. A newer, quicker-setting, more modern building material was needed to replenish the lost building stock, waving goodbye to the fussy, over-detailed houses of before and heralding a new era of functionality and clean lines.
However, as in so many other areas of society, we are increasingly paying the price for the hurry-up-and-get-it-done
approach to building. Many structures using non-permeable cements are cracking and failing before our eyes. Gypsum
plasters, cement mortar, petro-chemical paints, foam insulation and chemically injected timber all contain high levels of very
dangerous chemicals, and are all adding to what is termed, ‘sick-building syndrome’.
Thankfully, we are seeing a return to the old traditional ways of building. This turnaround has come about through a need to
reduce carbon dioxide emissions, to re-cycle and re-use perfectly acceptable building materials, and in a return to a more
individual style of building.To help responsibly sustain our planets natural resources and to lesson the damage that large
scale construction is wreaking on the globe. - what’s not to admire?