Control of water ingress into railway arches using Oldroyd Xv studded waterproofing membrane

The arches, which are located at Fieldgate Mews, London W6, are the property of London Transport. They are currently being used as a car body-shop, making a dry environment particularly important, as any new car paint-work would be ruined if water dripped onto it.

The contractors, R and D Sibley, were called in because the tenant was not satisfied with the performance of the existing waterproofing system (polythene sheeting secured to the soffit with plywood battens, falling into high level guttering along the sides).

Work Carried Out

The brickwork was inspected upon removal of the old waterproofing system. It was found to be constructed in sections with “open day” joints through which the rainwater was percolating. This rainwater had collected on top of the polythene sheeting causing it to sag and, eventually, tear.

The flashings over the gutters were deemed to be inadequate, being of mineral felt, glued to the brickwork with bitumen. These were removed and replaced with lead flashings.

All existing guttering was removed, together with the rotted timber spacing. New guttering was installed, fixed directly to the brickwork, laid to falls with the flashing dressed into the gutter.

Oldroyd Xv Clear waterproofing membrane was then fixed to the arch in the normal way, with all joints oversealed. To comply with London Transport Property requirements, 1.20 m × 1.20 m access panels were incorporated to allow for periodic inspection of the structure.

The works were completed on 21^st June 2002 after a total contract period of ten days.