Certain natural materials provide some of the best building fibres due to their performance and ease of use and maintenance. NBT founder Neil May has recently produced a paper on clay plasters in buildings, explaining how important they are and how useful they can be in standard renovation work, even in modern structures.
The Benefits of Clay Plasters
In terms of “breathability” clay plasters not only have excellent vapour permeability but also extremely good hygroscopic qualities which mean that moulds caused by condensation are minimised. We explain hygroscopicity in an earlier news post. Clay plasters have a much more rapid uptake of moisture from the atmosphere than with other materials such as timber, which take in and release large quantities of moisture but over a much longer period. They can therefore act to protect vulnerable organic materials (and in particular timber) from high levels of relative humidity, when microbial and insect attack can be triggered. Particularly with modern building usage (showers, cooking and indoor living) this can be an important strategy in the control of excess moisture in vulnerable buildings.
Clay plasters are flexible in relation to their fibre content and are able to hold together the plaster without cracking in situations of minor or gradual movement. This is a significant quality in old buildings. Clay plasters are reversible and re-workable provided they are not contaminated and, unpainted, have a very particular aesthetic. Clay also works extremely well with NBT’s internal wall insulation solutions Pavadentro and Pavawall.
If you would like more information on the suitability of clay plasters in retrofitting, read Neil May’s report here.