The Versatility of Clay
Images, Baillie Baillie
Words, Colin Baillie.
The Versatility of Clay
Taigh-bata is built primarily from clay and timber. The structural blocks used for the walls, the terracotta tiled floor, and the plaster internal finishes are all clay in various states. It speaks to the versatility of the material.
Clay plaster is made with unfired clay, typically mixed with sand, and in some cases, reinforcing fibres. As an abundant natural material, it’s quite possible to make plaster with raw ‘ingredients’ sourced on site, or as locally as possible. Utilising existing material from the site is likely to be the most sustainable way to source clay, and for future projects we’re very interested in establishing opportunities early in the design process. As well as clay, this might also include stone, timber, or perhaps straw in the case of agricultural sites. We carried out a ground investigation at our own plot, and realised we didn’t have a viable resource in this case.
Without a good supply of ‘wild’ clay to work with, we reviewed a range of products available on the market, before opting for a relatively new clay slip and base coat from a company called Womersely’s. Being Yorkshire based, they were the most local producer we could find. Their base coat is reinforced with hemp fibres, which we were interested in due to the excellent sustainability credentials of Hemp as a plant, and also the secondary benefit of some thermal qualities. Hemp is an excellent insulator, although in this case, it’s used mainly for its fibrous strength. A wet clay slip is first applied to the walls to aid adhesion, before a 10-12mm layer of the base coat (which also comes as a ‘wet’ clay as opposed to the more common powder form).
The material is quite beautiful as a finish, although we expect it to dry to a paler grey. When the moisture in the material is sufficiently reduced, we’ll be skimming over it with a thin topcoat from Cornwall-based Clayworks. This was an aesthetic choice, due to the colour and quality of light we felt was right for the space. Topcoats tend to be a finer mix of clay and sand, and are available in a wide range of colours.
It’s important to us to remain self-critical, particularly when it comes to sustainability. Clay is a natural material, which in many forms doesn’t need to be heavily processed. But it’s still an extractive material, and should be considered carefully. Two major benefits in using clay structurally is that it’s highly vapour permeable, and that when fired, it’s very robust, which should allow it to have a long lifecycle. It’s not toxic, and at least in theory lends itself to being recycled. Unfired clay has much lower embodied carbon, and where it can be sourced on site, with no wastage or transport carbon, it’s likely to be one of the most sustainable materials choices available.
