217 Rossal was designed and constructed using an innovative volumetric off-site method incorporating, CLT, nCLT and engineered timber as well as more conventional timber products. The chosen system provided an economical building using highly sustainable locally-sourced materials with low embodied energy, minimal environmental impact and a high level of carbon sequestration.
As part of the design brief the superstructure, including internal finishes and insulation, was to be of timber and timber by-products only. Exclusion of gypsum-based fire protection products resulted in the application of timber fire engineering techniques throughout the structure. Experimental systems such as nail-laminated timber were also employed. The unique system of prefabricated modules allowed the building to be constructed efficiently within a controlled workshop environment with the highest level of quality control. The modules could then be transported to site for rapid placement in combination, to form the complete two-storey building.
The structural form, nominally comprising of 6m x 2.4m single-storey modules, were stabilised by a combination of timber moment frames, CLT wall panels and traditional sheathed timber walls. Both floor and roof panels were long span plywood stressed skin units, with the design including investigation of dynamic response factors. Local and full scale load test were used as an integral part of the design process. The approaches combined advanced engineered timber products with design and testing methods to provide structural integrity in the modules and for the building as a whole.
The structural form of the building enabled a high level of optimisation of the foundations to minimise the volume of concrete required on site to a level far below conventional strip footings and blockwork under building, while still providing sufficient resistance to uplift and overturning.
The quality of the home environment thus created was exceptional.