Duration: 39 Weeks
Contract: NEC3 Option B
Walker Construction were employed by the British Rail Residuary Board (BRB) to carry out refurbishment works to the main roof, covering the original International Station as Network Rail want to bring the facility back into use. The station had not been used since ’Eurostar’, stopped using the terminal following its transfer to St Pancras Station.
Works involved the complete preparation and repainting of the supporting metal frame for the entire roof, inside and out. The roof area is in excess of 10,000m2. We carried out Planar Glazing sealant replacement and replacement of glazing catchment sheets. The existing ’Latchway’ roof safety system was re-commissioned, with some elements of the overall works requiring abseiling techniques to gain access.
The roof was over the five disused platforms, curved in profile and supported by 36 asymmetric three-pin arch trusses. Each arch truss consists of tubular steelwork which is located either internally (East side of the roof) or externally (West side of the roof). The roof extended approximately 400m in length and the arch spans varied between 35m and 48m. The Western portion of the roof presented the tightest radius of the train shed roof, with the Eastern half forming a flatter profile, comprising of stainless steel cladding interrupted at each of the 36 truss positions by a glazed ’eyebrow’. The glazed elements of the roof had experienced a series of breakages since completion of the terminal and therefore two types of glass containment system had been retrofitted to manage the risk of injury to those below. Throughout the roof structure there are various types of gaskets and sealants which prevent the ingress of water at expansion joints and other areas where adjoining materials interface. The roof has not been cleaned in accordance with the original maintenance regime and was very dirty, inside and out. The paintwork was also showing signs of ageing, especially externally and at the Southern end of the roof where it is particularly exposed to the wind and ultraviolet rays. A percentage of the existing gaskets and sealants were also no longer serviceable.
Due to the nature of the roof, it posed difficulties in access with considerable working at height along with potentially fragile areas. Access for plant equipment at platform level was restricted to equipment not exceeding a specific width and height due to the existing clearances of the Brute ramps. These Brute ramps provided access from the under croft areas of Waterloo Station and Waterloo Road, to the platform level of Waterloo International. In addition to these dimensional limitations, the platform areas consisted of different forms of construction and therefore had varying support loads. Plant was delivered to site prior to the erection of the temporary structural support to the floor on the external side of the curtain wall. Where possible we utilised mobile elevated working platforms to complete the works however we had to erect scaffolding specifically designed to produce a 20K/n per metre deck ’bird cage’, which was installed between the platform beds. The ’bird cage’ was constructed to staggered lengths of approximately 50 metres (approximately a third of the platform lengths. The ’bird cage’ produced a safe access/egress route between platforms. Due to the triangular formation of the major truss it was not possible to gain direct access to the underside of the East roof ’eyebrow’ glazing. Specifically adapted Youngman’s boards were fixed over the top chord tie members to gain access to comply with the recommendations of the original maintenance manual. Operatives were secured to the steelwork by inertia reel and full body harness to CHS tie members.
The external access issues were equally challenging with access being obtained via the use of full body harness and inertia reel system connecting onto the existing latchway system and suitable steelwork. Prior to project commencement, the existing man safe (latchway and anchor points) on the roof received a full inspection and recertification. An additional safe system of work was provided for work adjacent to the unprotected edge along gridline 2 and 37 of the roof line.