Control of Water Ingress Into Sheet-Piled Semi-Basement Plant Room in North London, UK

Project Background

The Undercroft (see picture) is located in the Swiss Cottage area of London. Its primary function is to house equipment to pump water from a borehole sunk into the chalk subsoil into a holding tank so that it can be used for irrigation and cleaning of the surrounding parkland (part of an urban regeneration project). The Undercroft also houses electrical equipment to control lighting and CCTV.

As the Undercroft is a semi-basement it was decided that a waterproofing system would be required to protect the plant and equipment from any potential water ingress from the ground.

The Waterproofing System

The main contractors, Durkan Pudelek turned to specialist waterproofing contractor Structural Sealant Services Ltd to provide a waterproofing solution. After a meeting on site with landscape architects Gustafson Porter it was decided that the Oldroyd Xv Clear cavity drainage system would provide the most appropriate waterproofing solution. This was because its use avoids the adhesion problems often encountered when waterproofing sheet piling.

Work Carried Out

Aquadrain drainage channel was laid around the perimeter of the room at the wall-floor junction by placing it into a pre-formed channel in the floor slab. It was ensured that the Aquadrain was laid with slight fall towards the front wall where weepholes were drilled to allow any water ingress to be discharged onto the paved and drained area outside the plant room.

Oldroyd Xv Clear cavity drainage membrane was then applied to the walls and floor, as shown in the diagram.

Special gun-fired fixings were used to secure the Oldroyd Xv membrane to the sheet piled walls.

A floor screed was poured over the Oldroyd Xv membrane on the floor. Once this had set, a blockwork wall was erected and plastered to provide a decorative surface.

Undercroft During Construction

Undercroft After Construction

The Completed Plant Room

The Finished Project

All parties involved were pleased with the result. Application of the Oldroyd waterproofing system was fast and clean allowing the contract to be completed on time and a Grade 3 dry environment in accordance was achived in accordance with BS 8102 as required by the client. This level of dryness allows the room to be used to house electrical equipment and control panels.