The Lark

Minimising embodied carbon in concrete-framed buildings

The Lark was built on the site of a former Royal Mail sorting office in Battersea. It posed several challenges typical of brownfield sites, with the most significant being the development’s location on top of a large Thames Water storm sewer.

Galliard Homes secured outline planning permission and commissioned Walsh in 2018 to facilitate design from detailed planning application through to delivery. The completion deadline was tight with projected completion in 2022.

To work with the proposed scheme, an efficient structural frame needed to be developed and early engagement with Thames Water regarding the sewer. The design had to fit with the architectural intent, keep the programme tight and, wherever possible, reduce cost.

By joining the project at an early stage, there was an opportunity to influence the design by optimising the grid and reducing the amount and type of concrete in the superstructure. To assess the embodied carbon and costs of different design options, various grids and slab thicknesses were compared, including post-tensioned concrete.

To mitigate the impact of the additional concrete in the sewer buildover and landscaped podium, a cement replacement was specified to minimise the carbon intensity. We had to work closely with the contractor to reassure them that using cement replacements would not have an impact upon their programme.

An embodied carbon calculation was conducted at both RIBA Stage 2 and Stage 5 of the project’s development. This revealed that we had reduced the estimated embodied carbon of the development by 30%. Of the total 30% reduction, 20% was due to less material, and 10% due to cement replacement.

Photography Credit: Peter Landers