COMMENDATION – 101 Moorgate, London

The 101 Moorgate commercial development is supported by a series of large trusses that span over a busy City of London station. 

FACT FILE
Architect: Orms
Lead Designer: Mott MacDonald
Structural engineer: Waterman Group
Steelwork contractor: BHC Limited
Main contractor: Mace Group
Client: Aviva Investors

Situated directly above Moorgate Station in London’s financial district, 101 Moorgate is a 10-storey over-station development that has created approximately 21,300m² of office space and 882m² of ground-floor retail in a prime location. 

The building features a double-height reception area, a mezzanine level business lounge, and multiple private and communal roof terraces that offer panoramic City views.

The challenging site constraints required the design and construction of a series of storey-high steel trusses, which span over the rail assets and support the structure above. 

“Structural steelwork provided a cost-effective, comparatively low-carbon solution to the challenge of working with the load limits on the top of the station box and clear spans over the rail infrastructure,” says Waterman Group Director Andrew Sherlock.  

The 60t trusses exceeded the onsite tower crane’s capacity and had to be fabricated and delivered in sections. As they are exposed in the completed building, the sections were site welded to achieve the required seamless appearance. 

The trusses are connected to four ‘bone’ shaped tension rods that support the building’s perimeter columns and façade via a series of 180mm pins. The rods are fully exposed and were designed be to an architectural feature within the building.

The steel transfer structure also includes four secondary trusses, which measure 12.5m-long × 5.2m-deep. Weighing up to 18t each, these trusses were fabricated and delivered to site as complete sections. 

Sat on top of the trusses, the steelwork for the office floorplates is founded on acoustic bearings, isolating this part of the structure from the station. The upper part of the steel frame is erected around three steel cores; one centrally-positioned main core and two secondary ones located either side.   

Perimeter columns are spaced at 6m centres and with only four internal columns, the open-plan office spaces have spans of up to 15m-long. 

“Because the rail assets are directly beneath the building, a lightweight structure was essential, so a steel frame with steel cores was the most suitable option for this project,” explains Mace Project Director Laura Thomas.

As well as its lightweight attributes, structural steelwork has also helped with the project’s sustainability aspirations. 

Achieving a BREEAM ‘Outstanding’ rating, the project team has sourced a high percentage of low-carbon recycled steel for the structure. Produced using Electric Arc Furnaces, powered by zero-carbon electricity, this is said to have resulted in a steel structure that has used significantly less carbon. 

Summing up, the judges say this is a very well executed project providing 10-storeys of over-station development above Moorgate station with all the complexities of transfer structures and acoustic isolation to be expected without compromising sustainable accreditation. Of particular delight was the double-height atrium where the storey-high exposed trusses were a true celebration of steel.