Waterproofing a Precast Concrete Tunnel

The EdCity development is a not-for-profit partnership between national education charity Ark and Hammersmith & Fulham Council. With £150m of investment, EdCity aims to build a place that will make a difference to local people in White City, including:

• Education and youth facilities: A state-of-the-art new primary school, as well as a nursery, adult community education centre, and a youth zone for young people
• Affordable housing and new community space: Providing 132 affordable homes for local people and key workers
• Office space: 10-storey, 95,000 sq/ft net office building
• Public realm: Public spaces and pedestrian and cycle routes, improving community transport and accessibility

Phase One of EdCity began in July 2021, starting with the primary school, residential, youth zone and office building.

The primary school opened in Autumn 2023 and Phase Two also began on the nursery, adult education centre and affordable homes. The project is due to be completed in 2025.

The project required a large service tunnel linking the energy centre to the other buildings within the EdCity development.

The project engineers Mason Navarro Pledge and main contractor Bowmer & Kirkland developed a construction strategy that utilised precast tunnel sections. In-situ concrete elements were also cast into place where the tunnel adjoined the other buildings and at changes in direction.

Finally, the boulevard above the tunnel is also used for pedestrian and emergency vehicle access. The design therefore had to allow for movement in the joints from settlement and future loading.

Newton and our specialist contractor ASF Waterproofing Specialists worked together to develop a two-stage solution. The first created an integral seal in the joints using PC 509 Rubber Acryl, a highly elastic acrylic rubber injection resin that was contained within the joints using 

HydroCoat 203-RM repair mortar and backing rods. As with all bonded systems, substrate preparation was a key element of the installation.

The second stage created an internal seal using HydroCoat Monoflex, a flexible waterproof bandage combined with a solvent-free epoxy adhesive. The result is a waterproof seal that is easy to install and has excellent adhesion over construction joints that are subject even to extreme movement.

The technique and sequencing for the base, sides and roof of the tunnel were all different, but still needed to provide a continuous seal along, around and through the whole joint.

Despite this, ASF were able to deliver an installation of Type A and Type B waterproofing to British Standard 8102:2022