Adam Weismann - Clay and Lime Renders, Plasters and Paints: A How-To Guide to Using Natural Finishes

Dedications

Phil Brown, Douglas Johnston, Peter Ellis and Ed Crocker for your invaluable time and help with editing individual sections of this book.

Jeff Orton, Julie Haddow, Bill Sargent, Ed Crocker (again!), P. D. Marlow, Douglas Kent, Ian Prichett, Tom Woolley, Carina Beyers, Bruno Bengamra and Nobuyoshi Yukihara for your excellent interviews and written contributions.

Kelly Lerner, Barbara Jones and Bruce King for your help with the building design details diagrams in .

The Princes Foundation for our scholarship to help fund our research travels to North Africa, Europe and USA.

Christian Topf for his outstanding design work on this book, and for his eternal patience with us.

Everyone at Green Books.

T his book is about using natural finishes based on lime and earth. These finishes can be defined as being natural because they have undergone minimal processing, and contain no synthetic ingredients. The finishes that we describe in this book are plasters, renders, paints and washes. A plaster is applied internally, whereas a render is applied externally. A finish can be defined as a coating applied to the surface of a wall, which functions to give protection to the walls from the elements (external), and from the wear and tear of daily life. It can also beautify a space by providing colour and texture.

The raw materials lime and earth are versatile and adaptable. They have been used for finishing buildings for thousands of years, throughout the world. They have always been used simultaneously for the buildings of the wealthy and the buildings of ordinary folk. The techniques and recipes that we have included in this book are therefore not new: they are drawn from centuries of use and experience, and through this book we hope to pay respect to all those who have laid the foundations for this simple, yet highly effective, ancient know-how. We also hope to honour all those who in the last thirty years have worked tirelessly to resurrect these techniques. Through this work they have helped to turn them from lost arts into well-researched and documented materials and methods. This is enabling them to be used ever-increasingly by the mainstream building industry with confidence. They are now therefore well on their way to becoming the obvious choices for creating homes and structures that are life-enhancing to live in, kind to the environment and healthy for the building fabric itself.

The techniques presented in this book stem from two separate but inherently linked groups: the people of the green building movement, that has been gently but powerfully emerging across the globe for the last thirty years, and the people involved in promoting the continued use of traditional lime and earth finishing and building techniques around the world. The bridge between these two bodies is that much of the philosophy behind the green building movement has grown from the common-sense building principles of traditional architecture. These principles include:

The local sourcing of materials, which supports the local economy, and also minimises the transport of materials over long distances.

The use of naturally sourced, unadulterated materials, such as earth (clay), stone, lime, wood and reed.

Building to fit into the surrounding land-scape and local ecology, so that buildings are site-specific and regionally distinct.

Building by hand and with individual craftsmanship. This means that all buildings are unique to the hands that made them, instead of being the result of materials bought off-the-shelf.

The techniques used are simple, accessible and easy to learn. This means that self-build predominates, and that all members of the community young and old, male and female can be a part of the process in some way. This can encourage the development of community and encourage the philosophy that the process of building is just as, if not more important, than the end result.

The green building movement has grown as a direct response to an accelerated environmental imbalance. An imbalance precipitated by the Industrial Revolution in the early nineteenth century. You will no doubt be aware of the undeniable link between CO2 emissions and climate change. Globally, cement production contributes around 5% of all CO2 emissions (source: The Economist, Jan 2008). Clearly, then, reducing the use of cement in building can play a significant part in reducing the negative impacts of the building industry on the environment.

An external earth plaster makes this building blend into its natural surroundings in New Mexico, USA.

Lime and earth-based finishes, used as alternatives to cement, can play a significant role in two ways. Firstly, as central components in all new-build finishes. Secondly, using lime and earth-based finishes (which are inherently softer and more porous than their cement counterparts), enables the use of low-impact, low-energy building materials. These are compatible in strength and porosity. Examples of such building materials include those made out of raw earth (cob, adobe, light clay and rammed earth), straw bales, hemp-lime and others. These building materials all produce less carbon emissions during their extraction, production and construction. Additionally, those materials based heavily on plant material, such as hemp, flax and straw, actually act to remove CO2 from the atmosphere. Through the growth of the plant material, carbon dioxide is absorbed, converted into oxygen, and then released into the atmosphere. Buildings constructed out of these materials generally also have good in-built insulation values or thermal mass (the ability to store heat), and can thus lower carbon emissions by minimising the need for heating a building.

Using lime- and earth-based finishes can also help restore balance to our planet in other ways. Though lime requires fairly large amounts of energy to produce (and requires quarrying), it has less impact than cement. The temperatures at which lime is fired are lower than those needed for cement. Lime manufacturing has the potential to become a localised industry throughout the UK, and indeed around the world, although at present many local, small-scale limestone quarries and kilns are out of action. Additionally, all forms of building lime reabsorb much of the carbon dioxide released during their production, back into the structure as it dries and cures. Cement products are one direction only, meaning that they are unable to reabsorb any of the CO2 released when they are fired. Lime is also recyclable and fully biodegradable. It can be crushed and then re-used as an aggregate in new mortars. Even when fully cured, it is soft enough to enable building units set in place or finished with lime to be dismantled, cleaned and re-used time and time again.