Most historic buildings are constructed using lime. It was used in conjunction with many vernacular materials according to regional differences. Brick, stone, earth and timber-framed buildings all relied on lime as a vital ingredient in mortar, render, plaster and decoration before the widespread use of cement, gypsum and modern paints became common from the 1920s onwards. Lime is slower to build with and requires skill and patience from the builder, but produces durable, attractive and healthy buildings. Damp was allowed to evaporate away naturally and the ‘soft but tough’ materials worked in harmony with seasonal changes in humidity and temperature.
Cement, gypsum plaster and plastic paints are universally available and there are very few historic buildings which have not had some modern materials applied to them. Likewise there are very few old buildings without some problems in the form of damp, peeling paint, crumbling plaster or flaking render. There is a link!
Repairing historic buildings with lime-based materials can often solve many of these problems, and will invariably prevent more form developing. Sometimes simply removing impervious plastic paint and replacing it with breathable lime wash can alleviate damp problems and condensation, providing the original lime plaster is in reasonable condition.
Environment & Health
Apart from the fact that most modern materials are unsuitable for using on old buildings, there are many valid reasons why traditional materials should be considered, even for use in new buildings. Cement, gypsum and plastics are generally ‘one way’ materials. Once used they cannot be converted back into their basic raw ingredients, and many are not readily biodegradable.
Cement, although it is processed in a similar way to lime, produces carbon dioxide during its manufacture, but does not reabsorb it when setting unlike lime, thus contributing to the problems of global warming.
A building constructed from traditional materials has caused less pollution to build and will eventually degrade in an environmentally less damaging way. Stone, timber and earth are also reusable, as is old lime mortar rubble which can become an ingredient in a new mix. In essence the elements in a traditional building can reproduce themselves.
In addition to the degree of pollution generated by their manufacture, many people find themselves increasingly affected by the vapours given off by modern paints as they dry and even by the low levels which continue afterwards. Sick building syndrome has been recognised as the result of modern materials in combination with poor ventilation, and can actually damage the health and performance pf people living and working in them.
Lime washes and distempers have been used for generations and are appreciated for their hygienic and mildly antiseptic properties. Lime plasters, washes etc. usually prevent both condensation and mould problems and an over-dry atmosphere. Their use is ideal both inside and out and can improve the living environment considerably.
Buildings constructed with traditional materials last a very long time with regular, sensible maintenance. There are thousands of such buildings to prove this. However, the use of modern materials when carrying out repairs must be stopped.
Modern houses are not usually built to last, and although they may need less regular maintenance initially, are actually much harder to repair once failures develop. Whilst there will always be a demand for large and exciting structures necessarily made with steel, concrete and plastics, is it the appropriate way to put together the bulk of our housing stock? Traditional materials age and mellow far more attractively than cement and plastic which merely become tatty.