One of the main benefits of offsite precast construction is obtained when a building frame has a limited number of variations throughout the component elements - something that is certainly not the case at the ongoing Kingston University Town House project.
A recent report on the Construction News website (subscription required) highlighted a number of compelling reason why, despite this, main contractors Wilmott Dixon urged the client to go down the precast route. Some of the precast concrete beams span up to 12m with the bulk of them 500 mm deep The article, by Paul Thompson, draws attention to a number of key considerations which resulted in the decision to bring in Willmott Dixon's category A specialist PCE Ltd for the provision of the structural frame.
Despite the lack of repetition, and a very complicated array of varying ductwork for services, cables and pipes - which are normally arguments against a precast approach - there were more important considerations, as evidenced in a quote from Willmott Dixon's senior operations manager Tony Mingoia:
"There are a lot of constraints on this site: it is quite a small plot; it is difficult to work on; there are certain design requirements. We recognised quite early on that using precast concrete was the best way forward for the frame."
The precast concrete elements are craned into place direct from the unloading area Gary Young of Kingston University Estates highlighted considerations for the decision - the challenges presented by such a small site and the fact that it is closely surrounded by other facilities. The precast benefits of a more rapid construction time and fewer people on site would effectively minimise inconvenience for those nearby. "The goodwill of our neighbours and the speed of erection on site were much more attractive benefits of the precast solution." Leaving the structural frame open to such close scrutiny means the surface finish needs to be of a very high quality
Kingston University had put the Town House project through a RIBA competition, according to Mr. Thompson, resulting in Grafton Architects' design being accepted. The resulting requirement is for the precast concrete frame to have completely exposed surfaces.
"This finished surface quality was one of the reasons the team went down the route of using precast concrete rather than cast in-situ reinforced concrete."
Overall, the Town House is set to create quite an impression, according to Mr Young who is quoted as saying that it has been a "fantastic resource" for the students:
"They are able to see the quality of building that a precast concrete structure can deliver."