Award Recognised Project

9 Millbank

This project is an exemplar in engineering tenacity and thoroughness. The team had to deal with real complexity to try and arrive at the lowest intervention solution.”

Will Arnold, Head of Climate Action, Institution of Structural Engineers

Reuse and renovation strategy significantly reduces cost, carbon & programme

This luxury residential development in the heart of Westminster consists of two phases; 9 Millbank and Millbank Quarter. The site has been subject to significant historic development. With complex refurbishments, Walsh prioritises finding existing information about the building, so through very detailed archive searches we located key pieces of information which greatly unlocked project value.

9 Millbank is the refurbishment and residential conversion of a majestic Grade II listed office building facing the Thames. The building, formerly known as Imperial Chemical House, was designed by Sir Frank Baines and constructed between 1927 and 1929 as the headquarters for Imperial Chemical Industries (ICI).

Structural alterations included forming large voids for new vertical transportation, partial infill of the existing atrium as well as a luxury business and leisure suite in the basement. A new swimming pool is to be formed, its position was carefully considered to avoid major remedial works to underpin existing foundations.

Millbank Quarter, comprises the demolition of an existing office Ergon House to form a 10-storey residential building. The existing double-storey basement was constructed in 1907 as part of the Westminster Power Station which used to occupy the site.

Whilst the previous engineer’s scheme had recommend the full demolition of the existing basement structure, our archive revealed substantial foundations up to 5m thick. We have justified the reuse of the existing raft which has been hugely beneficial to the project in terms of cost savings and programme – an estimated 10 months has been taken off the original critical path.

A key challenge of the foundation reuse has been to minimise the load of the new structure so we have specified and designed post-tensioned slabs to keep the self-weight of the building down sufficiently.

Awards

The Walsh teams, led by Ben Ransom and Garreth Joyce, were fantastic! Having spent days in the archives and researching trade journals from the 1920’s, they grasped fully and modelled the existing structures and developed the new build strategy around them. An example: the two-storey basement structure and foundations were designed for a four-storey power station. They introduced local enhancements to reuse these structures for the 10-storey new build apartments. Inspirational work!”

Mark Wakeling, Project Director, St Edward

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Taking Sustainability Seriously

Sustainability is in our DNA and we have our own ambitious goals to achieve Net Zero as a business and with our designs. With innovative in-house monitoring tools, Walsh clients have seen on average reductions of 10-20% total embodied carbon, with some of our flagship work achieving 60-70% reductions compared with baseline figures.