Mace has been appointed the main contractor by Investor Fabrix to deliver the 430,000 sq ft next-gen HQ office building, Roots in the Sky, in Southwark.

Erith has been selected as the enabling works contractor.

Mace will deliver the main contract for this innovative, net zero reimagining of the former Blackfriars Crown Court. Erith will deliver the basement box and demolition works as part of the two-stage construction process. The start on site date has been set for January 2023.

Roots in the Sky will provide over 280,000 sq ft of net lettable area alongside 46,000 sq ft of external terraces, including a fully publicly accessible garden and the UK’s first rooftop urban forest.

The appointment is a major milestone in the delivery of this transformational scheme designed to reinvent what a progressive and sustainable HQ office can be. The all-electric building will be net zero carbon in both construction and operation and is targeting BREEAM Outstanding, WELL Platinum and NABERS 5.

It features:

• London's first rooftop urban forest with 125 mature trees, 10,000 plants and unprecedented community access

• 1,000 tonnes of soil on the rooftop forest which will protect against flash flooding and reduces storm run off by over 30%


• Adaptability and connectivity with up to 45,000 sq ft floorplates accommodating up to 700 people on a single floor

• Low-level air supply and chilled beams providing best-in-class air quality

• Integrated waste energy capture, from areas such as tenant server rooms, which is injected back into the building heat network and used to heat the rooftop swimming pool

• Reclaimed steel from the demolition of another building, setting a new benchmark for the circular economy in a push to save more carbon

• Technology-led user experience infrastructure.

Designed by Sheppard Robson, the building delivers much-needed highly sustainable, quality office space, with unprecedented access to nature and community, at a time when occupiers are asking for more from their buildings.

The design reintroduces original features of the 1950s building through its façade retention, such as opening sash windows, which flood the spacious workspaces and six-storey atrium with light. Generous floor-to-ceiling heights of between 3.5 and 6.8 meters provide all-important volume, essential for the modern office.Natural influences inform the design of the interiors and finishes throughout, in keeping with the 1.4-acre urban forest on the roof of the building.

Fabrix is working with RHS Chelsea Gold Medal-winning landscape architect Harris Bugg Studio to introduce 125 trees and 10,000 plants, building a genuinely biodiverse space for occupiers and the wider community to enjoy. Local fauna will be introduced, including stag beetles, to support the establishment of an authentic ecosystem.

The highest value part of the building, the section of the rooftop with views of the City of London and the Shard, will be fully open for the community. Local people and the general public will have their own dedicated entrance and be able to enjoy the gardens, get involved in planting with access to potting sheds and seedbanks, and relax over a coffee or host events in the 3,000 sq ft community barn.

Circular economy principles have been prioritised in the design of the project. The structural solution incorporates reclaimed steel salvaged from a building being demolished in the City of London. Using reclaimed steel is 80% less carbon intensive than recycled steel. As a pioneer of ‘urban-mining’, Fabrix is the first UK developer ever to purchase second-hand steel for structural reuse.