Between 2003-2005 Gaia Architects were part of a team undertaking research work for a European Northern Periphery Project entitled Econo (a contraction of Eco House North). The international team (Scotland, Finland, Sweden, Norway, Iceland) explored methods of achieving sustainable timber houses. The Scottish contingent explored specifically the Brettstapel, method literally translated ‘stacked planks' - a form of un-glued massive timber construction. Originally conceived in the 1970s by the German engineer, Julius Natterer, Brettstapel has been used across Europe on a wide number of building typologies. Gaia Architects later became the first to use Brettstapel in the UK at Acharacle Primary School designed for Highland Council, and completed in May 2009. Brettstapel is not currently manufactured in the UK. The Brettstapel for Acharacle was procured from Austria.
The concept is quite simple: untreated softwood timber planks are fixed together with hardwood timber dowels. The differing moisture content of the two components (low for the dowels, higher for the planks) results in the two elements locking together as the dowels achieve moisture equilibrium with the posts. The process allows timber of intrinsically lower quality than the norm for building works to be used to form what is essentially a load-bearing, composite, structural element.
The components are typically assembled into prefabricated wall, floor and roof panels, often complete with windows, doors and some services. The finished building elements, which offer a high degree of air-tightness, can then be transported to site and erected very quickly. Brettstapel exposed internally can help regulate moisture and provide a degree of thermal mass. It offers acoustic control and maintains structural integrity during fire; and the use of such large quantities of timber sequesters a large amount of carbon dioxide.
By constructing buildings using Brettstapel, Gaia aim to highlight the opportunities for adding significant value to low-grade forest resources in the UK, e.g. Sitka spruce plantation. The technology has the potential to create jobs, generate revenue, encourage better practice sylvicultural methods, help the UK increase the rate of carbon dioxide sequestration (1.8 kg per 1kg of dry timber) and create beautiful, efficient, healthy buildings.
Gaia are currently working on a private house in the Scottish Borders - Plummerswood - using Brettstapel, which will be complete by late spring 2011.