STRAWBALES

This site was selected as the best location for the new straw bale buildings because of its proximity to the farmyard and its great views over the Shropshire hills.
The only conventional aspect of the project is the base. It consists of concrete strip foundations around the edge of the buildings on which approximately 850 concrete blocks were laid to form the perimeter walls which carry the timber frame structure.
The bales built at Brynmawr Farm uses the timber frame construction method. It comprises a timber floor insulated with 300mm of recycled bottle insulation on which is built a bespoke timber frame that sweeps around the curved walls of both buildings.
The frame supports a flat roof system with a generous overhang to protect the walls from the worst of the weather.
The sedum roof was built up in many layers; geotextile, butyl liner, water-retentive soil substrate two large skylights provide additional natural light to the large classroom beneath.
Approximately 250 bales of wheat straw have been used to form the walls of the two buildings. The straw bales is trimmed and shaped to fit in between the specifically designed timber frame. The straw bales is laid flat in the structure giving the walls an average width of 500mm. Once all the bales have been installed and compressed for maximum thermal value, they are trimmed to give a flat, rigid surface ready for rendering.
The render is built up in 3 coats inside and out. The first coat is a mixture of lime and sand worked directly into the straw to provide a firm key for the following coats. The second coat contains chopped hemp and is troweled onto the wall in a layer about 12mm thick. The top coat of render is a mixture of lime, a finer grade of sand, and hemp fibres.
Limewash is applied to the outside to give the render added protection and colour. The interior walls are finished with natural, breathable clay-based paint. Wooden windows and doors have been specified with 24mm argon-filled double glazed units to achieve good thermal performance.
Finally, the decking and access ramps were completed. The covered walkways provide weather protection and link together the main building and toilet block.