Project background

Acies was appointed to act as temporary works designer for work to expand existing critical care facilities at Chelsea and Westminster Hospital in London. McLaughlin & Harvey appointed Acies to act as temporary works designer. The project began in 2017 and finished in 2021.

Our involvement

We were involved with the design of a tower crane base and propping to remove a column, as well as checks on the construction methodology and sequencing for installing steelwork in the atrium. We also designed the permanent steelwork for the new Sky Garden adjacent to the internal walkway across the atrium at level five.

What did we do?

The main elements of the project were two separate single-storey vertical extensions on existing areas of roof and a partial three-storey infill of the internal atrium space over the main entrance to the hospital. The Sky Garden was to provide a green space that would be accessible from the new critical care facilities, where patients could sit and relax while taking in various art installations and enjoying the indoor planting. As with the atrium infill for the main works, this had to be constructed while the main entrance below remained in operation throughout. There were no restrictions on the depth of the structure beneath the Sky Garden, so long-span beams were designed to span between existing columns on either side of the atrium space. We undertook checks on the capacity of the columns to justify the additional loading, which demonstrated that no strengthening works were required and both reduced disruption below and minimised the cost of the structural works.

How did we do it?

Our knowledge of both permanent and temporary works and our experience of designing alterations to existing buildings meant that we were able to identify the best solutions for this challenging project.

What challenges did we face or help to resolve?

The project faced the challenge of working on not only a live hospital building but also a building located in Central London. The location of the critical care facility means that it is surrounded by buildings to all sides. The entrance below the Sky Garden was required to remain open throughout the works. This impacted both the design and the construction of the project.

How did we resolve those challenges?

Space for the erection of a tower crane around the site was very limited, so we worked with McLaughlin & Harvey to determine a suitable location that would allow the hospital to remain operational and to minimise disruption. The location chosen was constrained by a narrow strip of pavement adjacent to the road at the side of the hospital, which provided access to the service area at the rear. As such, an innovative piling solution had to be developed to allow for the forces exerted by the tower crane while avoiding several below ground services identified as being beneath the base through a ground-penetrating radar survey.

The steelwork erection in the atrium had to be carried out over the main entrance to the hospital while the area was kept fully operational. To allow for this, a construction methodology was developed working with the contractor, with truss elements being lifted in from above by the tower crane and access scaffolds spanning between the walkways going across the atrium. The propping to allow for the removal of an existing column was designed to avoid any back propping that would create restrictions at the floors below.

What impact did our work have for the client?

Our design for the structure supporting the Sky Garden, which was designed by Jinny Blom, artist in residence at Chelsea and Westminster Hospital, helped the hospital win the 2021 NHS Forest Award for the creation of an innovative green space.