Metek’s light steel infill walling system was used to create a curved façade with curtain walling and ribbon windows for Middlesex University’s three new multi-storey steel and concrete framed campus buildings.
Light steel infill walling has dramatically improved construction practice and has created new architectural opportunities that were fully realised at Middlesex University’s new buildings for arts, media and photography in central Hendon. The project comprises three steel and concrete framed buildings, the linked A/B/C blocks and separate D and E blocks, all designed by architects, Stride Treglown.
Metek was chosen by the management contractor, for this project because of their joint experience on similar projects, such as at Brunel University. The need to maintain operation of the University during the construction work meant that deliveries, site storage, waste and disruption had to be minimised, which was achieved by Metek’s light steel infill walling.
Buildings D and E used steel-composite beams supporting a composite slab. The long span steel system created spacious studios and teaching areas. The vertically curved façade and 7.5m column spacing with its 5m long ribbon windows, meant that in these areas, Metek’s infill wall system had to be designed to span horizontally between the columns rather than vertically between floors. This was achieved by using 150mm to 200mm deep C-sections to form a facetted curve to which the curtain walling was attached.
Importantly, to achieve the BREEAM ‘Excellent’ rating, the U value and air permeability of the façade and roof were very low. The wall U value of 0.18 W/m2K was achieved by 100mm of closed cell insulation (PIR) board externally, and mineral wood placed between the C-sections.
Cement particle board provided the weather-tight layer and ‘helping hands’ brackets fixed to the light steel C-sections supported the external curtain walling.
The project of 30,000m2 started on site in early 2010 and was completed in June 2011. The Metek package included supply and fixing of the cement particle board sheathing and the steel wind posts. The light steel infill walls and sheathing boards were installed progressively as each floor was concreted. The installation programme for Metek’s package was only 20 weeks. The overall project value of the 3 blocks was £54 million, and Metek’s light steel infill wall package represented less than 2% of this overall project cost, representing excellent value, and meeting the tight construction programme.
Site access was also very limited in the functioning University campus in North London. Bundles of C-sections were delivered daily in the correct lengths and sizes for the particular span and location.
Cement particle boards were also delivered as part of Metek’s package and boards were pre-cut to the correct size to reduce site work and wastage.
The light steel infill walls used 150 or 200mm deep C sections in steel thicknesses of 1.6 to 2.4mm. In the vertically curved walls, the C sections spanned 5m to 7.2m horizontally between the face of the columns. This orientation was required because of the vertically curve and the 5m long ‘ribbon’ windows in the architect’s design.
The rain-screen curtain walling was connected to extendable aluminium brackets fixed to cement particle board attached to the infill walls that formed the facetted curve of the facade.
In windows exceeding 5m length, wind posts up to 1.2m high using 70 x 70 SHS hollow sections were attached to the concrete floor slab so that the base plates fitted within the wall. Compound C sections passed over the wind posts, placed at 2.4m spacing, so that the required wall stiffness was achieved posts even for 7.2m long ribbon windows. Wind posts were delivered and installed as part of the Metek package.
Light steel framing is the preferred solution where weight saving and speed of construction are fundamental to the success of the project.