Right up to the present day, since 400 BC, lime mortars have been in constant use in domestic buildings.
In fact, if your house or outbuilding was built prior to 1900 it is almost certain to have been constructed of stone and built with a lime mortar used to bind the materials. Lime was the product of choice up until less than 100 years ago. The properties of lime make it superior to all other alternatives. Lime is unrivalled in its flexibility, durability, self-healing and ecological benefits; it actually consumes carbon dioxide in its curing process. We believe, unquestionably, if a building was constructed with lime mortar it should always be repaired with lime mortar - here’s why:
The 1930s witnessed what, at the time, was hailed as a ‘breakthrough’. Portland cement became widely produced. It was cheap, readily available and quickly replaced lime as the principal mortar used in the construction industry at that time. Cement was fast drying, fast setting and could be used in all elements, thus allowing for faster building and faster profiteering. As a consequence of living in a society where ‘time is money’ the use of lime became almost obsolete. Although cement was undoubtedly an excellent invention for certain applications, it does not suit all types of buildings.
Cement does have its disadvantages. Cement is acclaimed for its hard setting properties. This in itself can also be a problem when building or repairing a house constructed with stone. Cement can often be harder than the actual stone itself. As a result of this the cement pointing can actually lead to erosion of the stone, eating away at it gradually over time. This erosion causes gaps between the pointing and the stone, allowing the ingress of water. This moisture penetrates down the wall, with the potential to cause endless and expensive repairs: rotten joists, lintels, unhealthy damp and mould.
There must be great consideration given to the fact that cement is not a porous material. This is often regarded as the star feature of cement, but when cement is used in old buildings it is this very feature which causes the problem.
Any ingress of water that finds its way behind cement pointing/render (as water inevitably does) will undeniably remain there. It settles and pools, creating areas of damp which rarely disappear or dry out.
Buildings of traditional structures need to ‘breath’. There is a need for permeability, allowing the passage of moisture from within a wall to the outside surface.
Traditionally constructed masonry buildings were of permeable materials, like stone, cob or brick used with a permeable mortar to make them weather proof. These materials allow for free absorption and release of moisture through evaporation from their surface. In traditional buildings, damp is controlled by the very depth of the wall. This depth prevents the moisture reaching the interior, with the moisture being controlled by the natural rate of evaporation, known as breathing.
Cornish Traditional Masonry in Falmouth work across the whole of Cornwall in areas including Redruth, Truro and Helston.
As well as breathing, there is a need for movement in all buildings. Every building expands and contracts along with fluctuation in temperature and moisture levels. Buildings constructed using modern Portland cement are largely rigid and rely on the strength of the mortar to defy movement. This is where lime built constructions are unique. They are much more flexible and can accommodate a small degree of structural movement. This is possible through very minor movements across many mortar joints.
The need to move is often why a traditional building pointed with cement will fail. As the cement is often harder than the stone, the rigid structure of the mortar cannot allow movement and thus cracks. Whereas cement requires repairing by hand, the self-healing properties of lime will repair any small hairline cracks through precipitation of the lime itself.
There really is no real alternative to lime when accommodating the weatherproofing and sympathetic restoration of traditional buildings. It is ecologically friendly, absorbing CO2 through its gradual curing process, breathable, allows for movement and it’s self-healing.
Testament to the efficiency of lime is the thousands of lime built houses still standing proud after centuries. Lime is a material with purpose. A lime built house will harmoniously flow through the seasons, being protected by the elements.
A house originally built with lime should be repaired by lime creating a time tested, durable finish for your home, with the natural look it was originally created with.
Using lime on both old and new buildings, call us on: