Waterproofing of a huge double level basement in London

Challenge

This project was undertaken by the prestigious Galliard Homes to build 26 luxurious apartments with commercial space on the ground floor. Below ground there is a two level basement approximately 2000m2, this space is used as a gymnasium and changing rooms. Oaks Damp Proofing was commissioned to carry out the basement waterproofing works.

Solution

As this project was a double level basement a continuous waterproofing system was specified and designed by Delta’s Paul Callaghan CSSW to drain and manage any water ingress that may enter the structure below ground. Firstly a ‘Type B’ waterproofing concrete system was poured against the piles with a ‘Type C’ cavity drain
membrane waterproofing system (Delta System) mechanically fixed to the walls of both levels and a floor membrane laid across the lower level basement slab. (Delta MS500 and Delta MS20). 

Before the system was applied an anti-lime treatment (Polysil TG500) was applied to the new concrete to help prevent any free lime and mineral salt ingress which could build up within the membrane cavity and drainage channels and block it, potentially causing problems. 

As this below ground structure was such a large area two bespoke Delta packaged pump stations were placed within the slab on the lower level to collect the groundwater via. a drainage channel placed within the perimeter of the slab and pump it to the main drainage system.

The Polysil is also used as a primer to ready the concrete for the application of a ‘Type A’ waterproofing product which was used in various areas of the construction. (NB 1 Grey slurry, an in depth migratory crystalline slurry system). The NB 1 grey slurry was applied to the columns on the lower level approximately 1m high to mitigate any potential rising damp issues. It was also applied to the channels on the upper level and serviceable pipes were placed every 500mm through the intermediate slab so any water that may build up will drain down behind the cavity membrane on the lower level basement. The NB 1 grey was also used to waterproof the lift pits within the lower level basement, primed with the Polysil and a curved fillet installed at the wall/floor joint using Koster Repair Mortar Plus.

Outcome

This space was used for a Pure Gym open 24/7 with more than 220 pieces of state of the art gym equipment. As well as changing rooms with showers and lockers.