Structural Waterproofing

50 - 52 Welbeck Street

This refurbishment project in the heart of Marylebone was to increase the Grade A office accommodation to 17,500 square feet.

Experienced contractors, Virtus were appointed by Howard De Walden Estates to carry out the large scale conversion of the residential buildings into commercial space. The project to convert three Victorian buildings began with the enormous task of removing  600 tonnes of demolition waste which included the existing basement slab. The basement slab was replaced at a lower level to provide new high quality office space on the lower level floor. At the same time, a lift shaft was installed which meant installing a liftpit below the basement slab.

FIS worked alongside the architect and the contractors to design a full set of waterproofing details for the underside of the new lower concrete slab in the liftpit in the basement.

FIS proposed the use of Maxiprufe 2000 as a pre-applied Type A waterproofing membrane to be positioned beneath the slab. Hydroseal FX was also used to seal difficult details and old existing Victorian brickwork sections. The existing brickwork was injected too, to provide a retrospective chemical DPC to ensure there would be no rising damp in the masonry walls.

This was a challenging project with multiple interfaces with the existing structure. The refurbishment was a sympathetic process which meant the construction programme was a long one. Structural waterproofing design and detailing had to be responsive. FIS were on hand throughout the project and has to react to the structure that presented to them as the construction programme progressed.