CASE STUDY
STEEL
PUSHING THE LIMITS
1 Schooner Wharf is a mixed tenure housing scheme commissioned by Cardiff Community Housing Association that adopted passive solar design principles and is built to high environmental performance standards using the MetFrame system. In response to affordable housing priority needs, Austin-Smith:Lord were commissioned by Cardiff Community Housing Association to design a newbuild mixed tenure housing development in a prominent waterside location in Cardiff Bay. The houses and townhouses are contemporary in design and utilise a combination of traditional and contemporary materials. This creates a development that has a readily identifiable and fresh, modern character whilst also providing the sense of solidity and reassurance that comes from the recognisable layout and scale. The apartment block is constructed using light gauge steel offsite manufacture whilst the houses utilise timber frame kits. The Metsec loadbearing walls consist of 100mm wide vertical C section studs at max 600mm centres. Metsec components are rolled from pre-galvanised steel. All sections are cut to length and have holes punched to allow bolted connections. Walls are detailed in panels typically up to eight metres long by one storey tall that are pre-assembled offsite by Atkin Trade Specialists. The external face of the MetFrame external panels is clad with a 12mm cement particle board over which the external insulation
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is installed. Structural steelwork is integrated into the MetFrame system where required. Cantilever balconies and projecting bays are constructed from a hot rolled steel frame with galvanised finish and thermally broken from the MetFrame structure. These are installed when their supporting external walls are installed. The balconies are designed to allow a lightweight floor to be installed by others. Stairs are offsite assembled/fully welded units with in-situ concrete filled steel treads. They are fitted as each storey of MetFrame is installed. Lift shafts are included in the MetFrame. They have horizontal Metstrut channels bolted into the two side walls of the shafts for the lift manufacturer to fix to. Roof systems use Metsec joists typically 200mm deep at 600mm centres. This project follows on from a previous six-storey apartment block, delivered by the same contractor and design team, which was completed eight weeks ahead of programme by using the same MetFrame system. Lessons learnt from the previous project including a knowledge transfer partnership (KTP) with Cardiff Met University led to improved thermal performance of construction interfaces. The findings of this KTP led to better interface details for Schooner Wharf which in turn led to enhanced thermal efficiency and performance. The design adopted passive solar design principles and is built to high environmental performance standards which will reduce in-use costs. Fuel poverty is addressed through a highly efficient building fabric and energy strategy including use of renewables.
2 MetFrame was chosen as part of the wider environmental benefits it provides in addition to its cost and speed benefits. The offsite construction and detailed co-ordination prior to fabrication meant there was effectively zero waste and a low carbon footprint for the structural frame. The speed of erection led to cost savings and allowed other trades to commence work simultaneously. An average of five Atkin Trade operatives was required on site taking just 21 weeks to install the structure of the seven-storey apartment block. Given the site was constricted between a quiet residential development and offices, the speed of construction and offsite construction minimised noise, disturbance and disruption to the local community. Offsite construction generates up to 90% less waste than site-based building methods and achieves up to 90% fewer vehicle movements on site, compared to a traditional construction project – reducing noise, dust, congestion and carbon emissions. This project pushed the limits of the MetFrame system and required thinking outside the box to overcome the technical challenges of the design. For more information visit: www.austinsmithlord.com Images: 01-02. The apartment block is constructed using a well-understood offsite light gauge steel system. Courtesy Austin-Smith:Lord/Metsec
WWW.OFFSITEMAGAZINE.CO.UK | SEPTEMBER/OCTOBER 2020
