M25 Service Station Hotel, Cobham, Surrey

The construction of a hotel on the latest service station on the M25 at Cobham in Surrey had to be completed rapidly to meet the tight schedule for the project.

The hotel sector demands high quality, reliable and cost-effective buildings that are procured and built rapidly, and this has become an important market for Metek’s light steel framing system. The hotel chain Days Inn commissioned the main contractor to manage the construction of its 2-storey 72-bedroom hotel on the new M25 Service Station at Cobham, Surrey (clockwise between J9-10). The main contractor was also responsible for the construction of the adjacent service station, access roads and car parking. Metek was appointed as the designer, manufacturer and installer of the light steel structure, roof and the first floor composite slab.

The L-shaped building comprises a service and stairs area with two ‘wings’ of 40m and 30m length respectively and 14m width. The light steel framework is arranged as a series of cross-walls at 3.2m and 3.8m spacing, depending on the size of the rooms.

The cross-walls support a 150 mm deep composite slab using 80 mm deep composite decking that was un-propped during construction in order to avoid the need for temporary propping.

To speed up the construction process, BAM wished to install the pre-fabricated modular bathroom ‘pods’ by sliding them across the ground and first floors, and so 3.2m wide access zones were provided by using 150 mm deep slim floor beams spanning over these openings. The slim floor beams were fabricated as part of the Metek package and were embedded in the slab and supported by the light steel walls on either side of these openings.

The architecture of the roof involved a curved profile using a standing seam cladding system that projected outside the building line.

This requirement was achieved by using curved Rectangular Hollow Section (RHS) beams that were attached on the top of the light steel walls and connected to them.

The Metek build programme was only 9 weeks from start on site to completion of the roofing. The difficulty in accessing the site from the M25 meant that vehicle movement and deliveries were at a premium. Metek’s light steel framework was delivered in only 6 lorry loads and was installed in double quick time by the construction team. No waste was created, which was an important requirement also for BAM’s management of the site. The cladding consists of diamond shaped panels that are connected through the insulation to the light steel external walls and also brickwork.

3D BIM Model

Construction Details

The load-bearing walls all comprise 100mm deep x 1.6mm thick C sections, and the other walls use 100mm x 1.2mm C sections. The cross-walls were X-braced to resist the wind loads on the façade. The walls on the upper floor is supported on the slab below. The façade walls were essentially non-load bearing but were X-braced to stabilise the building in its long direction. In the 3.2m wide ‘corridor’ zone, 150x100 RHS beams with a welded bottom plate were used to support the underside of the composite floor slab.

The roof used curved 150 x 100 RHS beams that were attached on the top of the light steel walls and str apped to them.

These beams cantilevered up to 2.3m outside the building and w ere connected to external inclined cir cular hollow section columns of 6m height. A 230mm deep PFC section was bolted to the end plate of the projecting RHS and formed the cur ved eaves line along the building, and it also supported a deep perimeter gutter.

At the first floor level, the light steel cross–walls were manufactured to the form the facetted curve of the roof and 150 x 1.2 mm Z section purlins spanned over these walls and also pr ojected 1.3m at their ends to form a roof over-hang. Light steel horizontal wind girders were used to transfer the horizontal loads acting on the end gable.

The 150mm deep composite slab and its 70mm screed provide excellent stiffness, acoustic insulation and 60 minutes fire resistance with a single layer of plasterboard beneath. The floor slab was supported by the light steel cross-walls and was reinforced with 12 mm diameter bars in the ribs of the decking that also passed through the slim floor beams in order to tie the floor slab together for robustness purposes. The slab was designed to support a mobile scissor lift that moved around the first floor to allow the wall frames and roof purlins to be installed rapidly.

Light steel framing is the preferred solution where weight saving and speed of construction are fundamental to the success of the project.

Application Benefits

  • Curved roof formed using facetted cross-walls and projecting RHS beams
  • Restrictions on site access meant delivery of light steel panels was carefully timed
  • Un-propped composite slabs supported by light steel cross-walls
  • Rapid construction system
  • No waste on site
cobham under construction