Lime Plaster – a quick guide for building owners
From the simplest of shelters to the grandest of palaces it's natural to endeavour to protect one's home, both inside and out, with evidence of wall protection dating back to 8000 BC. In this article we explore the use and benefits of using lime plaster in your home
A brief history on lime
Lime plaster is a type of interior plaster composed of sand, water and lime, obtained by burning limestone, and often contained animal hair for reinforcement. Lime continued to be used in the construction of traditional dwellings over thousands of years and lime kilns were commonplace across the British countryside. Traditional building methods & materials developed slowly over the centuries until the industrial revolution of the 19th century after which the rapid expansion of products available continued to progress throughout the 20th century and mass production became the norm. The developments of modern building technologies and materials resulted in a sharp decline of traditional practices such as the application of lime plaster and its use became minimal. The post WW2 demand for quick-build, affordable housing meant the technology of construction changed as alternative, fast drying materials such as cement, gypsum and plastic paint became readily available. Because such materials set very hard and are impervious to damp, modern buildings are well suited to these materials which are now widely used across the construction industry.
But what happens when these modern components are used in historic buildings and how is this relevant to us today?
If your property predates WW2 then there is a good chance that the internal walls were originally coated with a traditional lime plaster, and if your home was constructed any time before the twentieth century then it’s a pretty safe bet. Therefore, if you have any intention of repairing, re-plastering or altering your internal walls take a moment to consider which methods and materials you might use and what implications this may have on your home in the future as the most obvious and available treatments may not always be the best option.
The mixing of two entirely different building technologies can invariably lead to problems if the underlying structure is of a softer and more flexible material, as it commonly is, undermining the building’s ‘breathability’ and causing moisture to be sealed in and cracks to appear. Issues such as peeling paint, crumbling plaster and damp in period properties are incredibly common and often to be expected as very few old buildings have escaped having modern materials applied to them. It is the strength, inflexibility and moisture resistance that can make the use of such materials in the repair of old buildings inappropriate. Unfortunately, many homeowners seeking professional guidance often find that they (or previous occupants) have been ill-advised in the use of modern plasters, mortars and renders, and further remedial work is necessary to resolve subsequent issues.
Traditional building materials need flexibility for seasonal movement without surface cracks appearing, and breathability so that any moisture from condensation or water ingress, commonly through external walls or chimney stacks for example, can escape and dry out.
Any moisture sealed into fabric of the building can be extremely detrimental to the structure if it is able penetrate but cannot dry. Often recommendations to treat damp issues by quick-fix ‘Tanking’ – where studs & plasterboard are fitted internally over the problem wall and skimmed with modern cement plaster– simply mask the problem and walls left unchecked behind such an installation may suffer costly damage.
Typically, the Internal walls of domestic dwellings would traditionally be constructed using timber, brick, stone or lath. Lathes are narrow strips of timber nailed horizontally across the stud wall frame or ceiling joists, similar to the more basic ‘wattle & Daub’ used throughout the medieval era. Lath is the most common internal wall construction method in buildings erected between 1700 and 1940 and therefore understanding how to care and repair walls of this type are critical to the successful maintenance and alteration of a high proportion of UK homes. The plethora of problems in domestic buildings resulting from the DIY boom of the last decades of the twentieth century and into the millennium has resulted in a revival of many traditional building methods, most notably the reintroduction of internal lime plastering.
Moreover, the use of lime in building could be considered an 'ecologically healthier' option in period building repairs and in new extensions or self-build homes. Although the manufacture of both lime and cement result in the production of CO2, unlike cement the lime reabsorbs CO2 during its application and throughout the drying process.
In addition to lime plaster being an altogether more suitable material for the period home, appealing to both the amateur and professional renovator. Modern materials can often be so quick drying they leave little room for error, whereas working with lime can provide time for adjustment and alterations. Owners of Listed Buildings in particular are the privileged custodians of the country’s built heritage and have a responsibility to ensure that works they carry out to the building remain sympathetic and most importantly compatible with traditional construction.
Many professional companies now offer lime products and techniques in their portfolios, or for those wishing to learn a new and useful skill there are suitable day and weekend courses available through various organisations nationwide. Further information and a list of courses can be found on The Building Limes Forum website at www.buildinglimesforum.org.uk
Ultimately, for current or prospective homeowners of listed buildings and traditionally constructed properties, the resurgence of traditional building techniques such as lime plastering, and the abundance of quality knowledge and resources is a positive step for continued good conservation practice. At ArchiWest we specialise in older properties of all shapes and sizes, providing the specialist expertise required. For more information and help with your project get in touch here.
studio@ArchiWest.co.uk - 01934 311017
Useful further reading on the subject; Jane Scofield – Lime in Building. A practical Guide. Revised 3rd Edition.