Construction strategies To maintain the sustainable aspects of the scheme, an early decision was made to use cedar shingles on the sloping roofs. However, the cedar shingle roof constituted a risk for spread of flame so the rafters have been overdrawn with a layer of calcium silicate board to provide 30-minute fire protection. Isonat, another hemp-base product made with recycled cotton fiber and a thermoplastic binder has been used to insulate the roof. Sedum roofs are a high performance single layer felt which provided waterproofing to the flat roofed store areas, and is overlaid with insulation, deck, protection fleece, drainage layer, substrate and sedum planting to provide an ecological protection layer which improves the surrounding air and water quality whilst further lowering carbon emissions and sustain a wildlife habitat. The dwellings have timber frames that were partially prefabricated in sections off-site.
To brace the frame of the walls 12 mm Sasmox sheathing, a gyspum reinforced fibreboard, was fixed on the inside. The walls were insulated with Hemcrete, a mixture of hemp, hydrated lime and a small amount of Portland cement as a binder to accelerate the curing process to set a rigid, breathable layer. The Hemcrete was mixed on site and sprayed onto the timber frames to ensure there are no gaps that might compromise air-tightness.
The use a prefabricated element ensures that the time to build is less however there would be an increase in cost and a greater need for specialized workers during construction. On the gable walls the Hemcrete was finished with 20 mm of lime render. The window openings on the gable were lined with 25 mm Heraklith wood fibre boards to form a square reveal and the lime render is returned into the reveals. Curved walls provide privacy and enclosure to the gardens.
They are built from unfired clay blocks rendered both sides with lime render and capped with a cedar shingle coping.