Metek UK Ltd creates an innovative mixed precast concrete and light steel hybrid construction system for 17 new 5-storey residential buildings.
The University residential sector is expanding rapidly as student numbers and expectation of the quality of the academic experience increases. Brunel University in Uxbridge is expanding its en-suite student accommodation on its West London Central campus by 1,400 with the mid-2008 completion of 17 new five-storey residential buildings.
The £56 million project was a design and build contract for the contractor. The primary structure of the buildings is a novel ‘hybrid’ of precast concrete cross-walls and floors, and light steel façade walls and parapets.
It is essentially a ‘dry’ construction technology, which optimises the speed of construction, and early start for follow-on trades, Architect Stride Treglown’s design consists of similar shaped buildings each with two wings either side of a central lift and staircase. Each building contains 80 to 100 rooms, all with a toilet-shower ‘pod’, and have shared kitchen facilities.
The project started on site in November 2006, with piling for the foundations. The steel and precast construction started in April 2007 with completion of all 17 blocks by December 2007, four months ahead of contract programme. Hand-over of the 17 buildings was in July 2008.
Modular lift over-run units were pre-fabricated with integral 203 x 203 x 60 kg/m beams to support the lifts (by Kone). These units were delivered ‘just in time’ from the Metek factory in Wolverhampton and lifted straight from the lorry onto the roof, which reduced the need for storage on site and eliminated waste.
The cladding consists of brickwork and insulated render, which was placed on cement particle board (CPB) that was pre-cut exactly to size and screw fixed to the light steel wall panels. The X-steel computer ‘model’ of the structure and wall panels was used to pre-order and manufacture all the components, including insulation and CPB.
The 5-storey structure of the buildings consists of twin 180 mm thick party walls constructed of 2 leaves of 55 mm concrete with self compacting in-situ infill, offering the benefits and integrity of in-situ construction with the quality of finish attained using high quality precast concrete for direct painting.
The slabs are 2.5 m wide, 65 mm thick composite units with 110 mm topping for integration of services and direct soffit decoration. Service holes are preformed and polystyrene infill seals the holes during construction.
The 2.6 m high light steel infill walls used to create the façade were installed as prefabricated panels using 100 x 1.2 mm C sections nominally at 600 mm centres. Windows are 1.8 to 3.2 m wide using single, double or treble C sections detailed around the windows for local strengthening.
At roof level, 1.0 m high light steel parapets were designed, again using light steel panels, supported by Square Hollow Section posts at the cross-wall positions.
Lift over-runs were manufactured as light steel modules. The installation of the light steel framing for the façade walls reached a rate of one building every 2 weeks.
The Metek contract also included the cement particle board used to support the insulated rendered cladding, which was pre-cut off-site to minimise wastage and increase speed of installation.
For the elevations with brick cladding, Metek also installed the 55 mm thick insulated panels and brick-tie support units, which again led to a smooth ‘hand-over’ to the cladding contractor.
Light steel framing is the preferred solution where weight saving and speed of construction are fundamental to the success of the project.