Taking inspiration from its natural surroundings, the new Pump House at Kew Gardens is part of a wider scheme to provide a greener source of irrigation and improved water security. It was built on a JCT Intermediate Building Contract with contractor’s design.
Kew Gardens in Southwest London houses the largest and most diverse botanical and mycological collection in the world. With over 50,000 species, the UNESCO World Heritage Site – a 121-hectare landscape – requires a considerable amount of water to maintain its environment, especially as the world grows increasingly warmer.
A summer drought in 2022 (which resulted in the loss of 400 trees) prompted a rethink. In addition to a new plan to refocus on the types of species they would plant in future, they were also forced to reconsider their existing infrastructure. With a set-up reliant on the use of mains water, they realised that this would not be a long-term sustainable solution.
The answer was to add a new Pump House, which draws water up from an underground tank to irrigate the gardens. Designed by Hugh Broughton Architects, with CityAxis Ltd as the main contractor, it was developed in collaboration with the horticultural and capital projects team at Royal Botanic Gardens Kew. The Pump House, in addition to harvesting more rainwater, forms part of Kew’s new irrigation strategy to ensure greater long-term water security, reduce reliance on mains water, and work more harmoniously with nature. It is an ambitious project, with the overall goal of being climate-positive by 2030.
The Pump House – the heartbeat of the new irrigation network – comprises an underground water tank that stores 280,000 litres of irrigation water. Atop this, on a small mound, sits the building itself. It is a simple timber structure of interlocking struts forming sharp, angular walls that curve around and oval-shaped enclosure, which protects the machinery housed within.
In a similar way to its neighbouring Treetop Walkway (designed by Marks Barfield in 2008), the Pump House’s design draws on the natural environment. Viewed from above, its shape, and the autumnal hues of its naturally finished European larch timber construction, mimics that of a fallen leaf. This will age over time to a silver colour.
The structure of its interlocking timber struts references a palm frond. The dappled light reflected from the angles and spaces between the timber, along with the shadows of the surrounding trees, subtly blends the building into its environment and helps conceal the Pump House’s inner workings.
The design was built up and developed through the creation of dozens of sketch studies of leaves and leaf structures, seed pods, and palm fronds. From these hand drawings, 3D modelling was used to help create the nature-inspired final sculptural design.
It is a beguilingly simple and striking building for one that serves a very functional purpose, albeit one that also carries a degree of complex building services. The JCT Intermediate Building Contract with contractor’s design is an effective and appropriate contract where just such flexibility is required to capture a wide range of form and function.
Project data
Start: November 2023
Completion: July 2024
Gross internal floor area: 22m2
Gross (internal + external) floor area: 110m2
Client: Royal Botanic Gardens, Kew
Architect: Hugh Broughton Architects
Main contractor: CityAxis Ltd
Contract: JCT Intermediate Building Contract with Contractor’s Design (2016)
Structural engineer: Stantec
M&E consultants: Stantec, Spencer Mayes
QS: Firmingers
Building energy management consultant: Kendra
Pump supplier: KGN Pillinger
Project manager: Royal Botanic Gardens, Kew
Principal designer: CityAxis Ltd
Registered building control approver: Regional Building Control Limited
Specialist timber design and fabricator: Xylotek
Specialist steel design and fabricator: Rank Engineering
CAD software used: Autodesk Revit, Rhino, SketchUp
Images: Dirk Linder