Project Overview

The 17-storey hybrid timber (cross-laminated timber) building has been designed to offer c. 26,500m2 of commercial office space alongside more than 230m2 of retail space on the ground floor. It will also include more than 2,650m2 of affordable workspace offered at a discount to the market. Positioned above Southwark Tube station, the building will retain the station entrance, ticket hall, and lightwells down to the Jubilee line platforms.

Notable impact:

Climate Change: All-electric energy design, enabling operational carbon emission reductions as the national electricity grid is decarbonised. The building will be enabled to achieve net zero carbon in line with UKGBC and LETI definitions. Includes air source heat pumps and PV panels.

Resource Use: Cross-laminated timber (CLT) was chosen on environmental grounds, but also financial viability. The choice of a steel and CLT structure reduces the deliveries to site compared to a steel/composite deck structure. On-site construction practices for CLT means a higher Considerate Contractors Score can be achieved. Off-site manufacturing minimises water and material waste in construction, reducing the environmental impact.

Nature and Biodiversity: Biodiversity Net Gain of 88% is targeted. Baseline habitats are negligible ecological value give site is over an underground station.

Health and Wellbeing: Biophilic features, mixed mode ventilation, outside space (balconies) to be provided on every floor. Air quality neutral to be achieved in regard to both transport and building related emissions. Step-free access to all parts. Large quantity of basement level secure cycle parking facilities. Unisex accessible facilities positioned so that any disabled persons will not have further than 40m travel distance. Gender neutral facilities are to be provided on every level.

Socio-economic Impact: Proportion of space to be let at below market rates. Offered to an affordable workspace operator for, at most, 70% of the market rent.

Key Sustainability Objectives/ Outcomes

  • Targeting a rating of ‘Outstanding’ for BREEAM, the highest available.
  • Targeting a WELL Building Standard rating of ‘Platinum’, the highest rating available, demonstrating  a commitment towards providing a healthy environment for building occupants.
  • Signed up to the NABERS UK design for performance scheme, which rates the energy efficiency of office buildings through design construction and occupation. Aiming for a design review target rating of four to six stars.
  • Scoring the property under TfL’s Sustainable Development Framework (SDF), where the Over Station Development is currently TfL’s highest performing proposed development.

Notable Approaches And Solutions

The existing station was built as part of the Jubilee Extension in 2000. The existing foundations were meant to support a different lower rise building, which was not built due to viability problems. TFL undertook a number of studies to find an approach and material that could support greater height, and had outstanding environmental features and the result was to use CLT. The use of CLT results in a whole life carbon figure 26% less than the total whole life energy figure of the concrete option. Concrete composite would result in 7% lower operational energy consumption but 79% higher embodied energy.

Lessons Learnt

TFL investigated the structural properties of a building made entirely of CLT, which was not a viable opportunity. The structure needs to be hybrid in nature to achieve the height required to obtain the massing. The hybrid solution chosen was to keep a concrete base around the existing station from levels B2 to 1st floor, with a concrete core, steel frame and CLT floors. The lighter weight of the CLT also meant that we were able to gain a couple of floors.

Many planning challenges were encountered due to working around an existing station. The fact that TFL have a station at ground level, and two basement levels, meant that they have had to be creative to find cycle parking solutions, alongside all the room for plant and equipment.

The key to unlocking the site is a land exchange agreement, and also the stopping up of a highway which allows us to get the footprint and critical mass. The agreement is with London Borough of Southwark who own a residential estate next door and this is a fine example of how two pubic bodies can work together to  enable the delivery of affordable homes and offices.

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