Sika makes it a watertight case for £440 million revamped shopping centre

Currently undergoing a £440 million facelift and major expansion, the redevelopment of Oxford’s Westgate Shopping Centre has seen the specification of a comprehensive range of Sika waterproofing solutions which will ensure this major retail development will be protected against the harmful influences of groundwater at the riverside location.

Located in the heart of the historic city of Oxford and built in 1972, the existing shopping centre is being transformed by main contractor Laing O’Rourke, with the new expanded 14 acre development set to include more than 100 new stores, 25 restaurants and cafes, a new cinema and rooftop terrace, and a 1,000 space basement car park. With the site located next to a river, engineers Waterman Group required a complete tanking system for the basement areas that could prevent lateral water movement.

In order to seal the basement car park slab and the reinforced concrete walls, the specification included more than 35,000m2 of the Sikaproof® A08 and A12 system, a totally new concept in membrane barrier design to deliver outstanding levels of watertightness to the lower floors.

Andy Edwards, Sika Specification Manager, Waterproofing commented: “SikaProof A is a highly effective waterproofing membrane and the perfect solution for a project with a high water table. The flexible nature of SikaProof A also proved ideal for the level of detailing required for the sheet piles.”

The membrane surface of SikaProof® A is embossed with a grid pattern, which contains a sealant, and is topped by a thin layer of fleece which forms a mechanical bond to the concrete when it dries. The grid pattern is also unique. It offers additional protection, due to the integrated sealant, which bonds tightly with the surface of the concrete, forming mini watertight compartments. Therefore, even if the membrane is damaged or pierced, moisture or pressured water cannot spread between the membrane and the concrete structure as it is contained within the small damaged grid square.

To complete the system, construction joints were sealed with the SikaSwell® jointing system, which consists of joint sealing profiles that expand on contact with water to seal any voids between adjoining concrete slabs.

With the Westgate Oxford shopping centre scheme set for completion in the autumn of 2017, the application of highly reliable and durable waterproofing solutions from Sika has ensured this landmark development has a watertight future and remains on track for completion.