Surface tension at Hongluo Clubhouse near Beijing
The Hongluo Clubhouse, by Beijing-based MAD Office, uses curved steel sections to create a roof structure that blurs boundaries with the surrounding landscape
Lake Hongluo is located to the north of Beijing and the Hongluo Clubhouse serves as a community centre for a rapidly expanding suburb of China’s industrial capital. The clubhouse appears to float in liminal space. The digitally designed steel-framed enclosure responds to context, mediating between the mountains and the tranquil waters of the lake.
The Beijing-based architects, Ma Yansong and Yosuke Hayano of MAD Office, say the structure, which was completed in 2006, is meant to appear to ascend from the lake itself. As the practice states:
“A continuous, reflective surface rises up out of the water, becoming first the roof and then the walls of the clubhouse. This surface blurs the distinction between solid and liquid states, between building and environment.”
I started to research this project when it won an architectural design award in 2008 and the judges praised its curvaceous roof. The roof was built from a framework of curved steel sections which were clad on site with plywood. The project was tendered with doubly curved 2mm aluminium sheet, but this was revised by the contractor as it would have been difficult to detail as drawn. Instead the plywood was coated on site with glass-fibre-reinforced epoxy resin, exploiting the inherent flexibility of GRP, while the outer surface was painted silver.
The design intent of this project is atectonic, the role of the flowing folded roof surface is to define space and provide reflectance. The materials are not used in an expressive manner, however the architects have fully exploited the qualities of steel particularly its formability and strength.
The primary route to the clubhouse is a gully-like walkway 1.3m below the surface of the lake. The architects wanted visitors to feel as if they were walking through water to get to this venue. The route is faced in stone and opens out into an exhibition area.
The clubhouse is also tethered to the shore by two timber bridges, which lead to terraces sheltered by the cantilevered roof. The glazing line is set back to form these spaces. The interior is a flowing space with a core that encloses the kitchen. The architects intend this space to be defined by the users and not the architecture. At the western entrance, the asymmetrical wing-like roof folds down to form a valley appearing to envelop the lake.
Adjacent to this entrance and just a few steps from the bar is an outdoor swimming pool. The water of the pool is kept precisely at the same level as the lake, and is just one of the many examples of how the architects have created a dialogue between artifice and nature. Their aim is to blur the boundaries between inside and outside, between intervention and nature.
Achieving the smooth transitions of the clubhouse’s doubly curved enclosure was not a simple process. However this is not the space-hungry strategy often used by Frank Gehry on projects such as the Bilbao Guggenheim. The clubhouse’s opaque construction remains within a 330mm zone. At the core of the wall/roof build up are preformed 200 x 100 x 8mm galvanised steel rectangular hollow sections. Typically these sections form the north-south sections, which on the tender drawings are linked together with 160mm steel channels. This has been replaced by a bricolage of square hollow steel sections which are clad on the outside with two layers of 8mm ply. This is topped off with waterproof layers of glass-fibre-reinforced epoxy resin.
This is an architecture driven by a fascination with surface. The underside is similarly clad but with only a single layer of 8mm ply that is plastered and painted white. The roof is in essence a propped cantilever, held up by 150 x 8mm steel circular hollow sections. The west elevation is reminiscent of the gull-wing doors of a Mercedes-Benz 300SL Coupe, except for the tubular steel columns.
The single glazing comprises two layers of 8mm laminated clear float glass that typically spans 3,580mm — framelessly. It is supported at the head and base by concealed steel angles that are integrated into the floor and roof build up. The continuity between interior and exterior is emphasised by the resin floor that extends beyond the glazing line — it stops inline with the inner surface of the roof or wall. The visible edges of the insulated concrete floor are finished to match the roof — it is expressed as another plane. Generally, the visible detailing of Hongluo Clubhouse is spatially well resolved. However, a glass balustrade adjacent to the eastern entrance appears to be competing for the same zone as the opaque roof/wall.
The building is not a good precedent in terms of thermal performance — it features single glazing and 60mm of insulation in a zone that could have been filled with at least 200mm of insulation. The vapour check layer appears to have been omitted by the contractor, which is a cause of concern for the long-term durability of this construction. The clubhouse demonstrates key differences in building regulations between China and Britain, when studying precedents from world architecture, the cultural, climatic and regulatory differences should be borne in mind.
Manufacturing curved steel
To investigate how difficult it is to bend steel sections that can support a doubly curved form such as Hongluo Clubhouse, I visited to Barnshaw Section Benders in Wolverhampton.
Barnshaw has developed its tooling over the past 40 years to virtually eliminate distortion of the section when bending. It can curve a 200 x 100 x 8mm rectangular hollow section down to a radius of 1,500mm and 140 x 8mm circular hollow section to a minimum radius of 785mm. The company’s CNC bending machine is capable of curving Corus’s largest universal beam, which is 1,016mm deep. Tremendous pressure is required as the yield point of the section needs to be overcome.
Barnshaw no longer uses induction bending, having developed cold bending processes that are more economical. These use three asymmetrical rollers; for an open section it is vital that the flanges are pulled opposite where it is under pressure, to ensure that the web of the I-beam does not collapse.
When bending closed sections, it is essential the hollow of the section be supported by a mandrel. There are aspects of this process that Barnshaw considers a trade secret and commercial director Greg North described section bending as a “dark art”. Even though its latest machine is computer controlled, it is operated by a skilled worker.
Although Barnshaw uses cold bending processes, it can achieve tight tolerances. For example, for sections up to 500mm the tolerance on the diameter is ±2mm. However they are willing to investigate even tighter tolerances.
Barnshaw works with a full range of metals including stainless steel and aluminium. Using asymmetrical bending machines the radii can be varied at will and thus it can work to digital co-ordinates, a skill honed in the building of amusement rides. A recent project is the steelwork of the monorail for Heathrow’s Terminal 5. The manufacturer can curve circulation sections up to an external diameter of 1,067mm, using concave hardened steel tools.
Curving steel should no longer be considered expensive, curving a 20m-long x 457mm-deep universal beam costs about £100 — significantly less than cutting, welding and testing a faceted beam of the same dimensions.
Michael Stacey is professor of architecture at the University of Nottingham and director of Michael Stacey Architects.