Prefabrication of major components such as walls and floors can have distinct advantages for construction such as increasing speed of erection and quality control. In what is being claimed as a new record, prefabricated structural wall, roof and floor units have been used to erect 10 complete house shells in only five days. Undertaken by Warwick Group Construction for CDS Housing in Liverpool, the Harlow Park project was designed by architect Parry Boardman & Morris to minimise running costs and use building materials from recycled or sustainable sources.
The project used a single panel to create each complete ground floor or first-floor wall, with three cassettes to construct each floor deck and four roof plates to provide each roof. Delivering a U-value of 0.19 W/m 2K, the system was also specified to reduce spaceheating requirements, with each property estimated to cost only £1-£2 per week to heat, and consequently reduce the amount of CO generated.
The houses have been designed to achieve a SAP rating of 100 and an NHER of 10.
Based on 'breathing wall' technology, TRADIS has been designed to combine the performance offered by 'breathing walls' with the erection benefits of a factory-engineered product, including dimensional accuracy, consistency and quality-control. The structural wall panels, roof plates and floor cassettes are manufactured from Masonite beams and Warmcel insulation, manufactured from recycled newsprint, sandwiched between internal and external sheathing. Water vapour produced in the household is allowed to migrate through the house structure and be expelled to the outside atmosphere, helping to ensure a healthy environment for the occupants.
Fillcrete believes that a common criticism of prefabricated housing - that it all looks the same - has been addressed by the system's versatility.
Outside, the walls can be clad in any material, including brick slips, and doors and windows can be placed anywhere in the panel. Indeed, the company hopes to be able to supply wall panels with fully glazed windows and door frames already in place, so that the building interior is weather-protected once erected. Inside, the structural strength of the loadbearing floor cassettes - 8m can be spanned without support for normal domestic loadings - ensures that the internal layout for each house can be different.
Because TRADIS was also used to construct the roofs of the two- and threebedroom houses at Harlow Park, each property has been designed to make use of the roof space, a space often wasted in traditional cold roof designs.
The roofspace needs no further work or adaptation for extra useable living space.