The Watershed – designing the indoor street

Imagine an interior that is designed like an exterior. The Watershed is an unconventional retail space firmly grounded in green design principles.

Cape Town’s Victoria and Alfred (V&A) Waterfront’s exploration into redeveloping an existing warehouse, which previously contained the Blue Shed craft market, into a multi-functional building, was an opportunity to re-imagine not only the concept of how small-scale retail should function, but also how interior spaces should interact with each other.

On an economic level, the Waterfront wanted to use the new building, now called the Watershed, as a platform for emerging small and local businesses in the creative design, arts and crafts sectors.

Although the Watershed was initially registered as a pilot project under the Green Star SA Interiors tool, this application is currently on hold, however, the Watershed is still lined up for Green Star SA status.

The core architectural concept is a generous open ended internal street that runs the length of the existing building, connecting the Two Oceans Aquarium on the west, to the rest of the Waterfront (a previously dislocated connection).

Two upper levels, which include a business incubation hub and a wellness centre, flank the sides of the building, and a large suspended steel floor for open exhibitions hangs 3.5m over a craft market space below.

Other facilities include a large exhibition hall in one corner, permanent retail units, and other public ‘street’ functions, like small green pocket parks and seating spaces. “Instead of a building, we made a network,” says architect Heinrich Wolff of Wolff Architects.

Permanent vs temporary

The interior fit of the building happens at a few different scales, explains Wolff, and varies between permanent or temporary in nature, which is also expressed through the construction and use of materials.

Inside the existing envelope of the warehouse there are a few permanent insertions, such as the concrete cores that contain the fire escapes, lifts and services. The strength of the existing structure provided the possibility for suspending the business incubation hub and the mezzanine floor above the ground without adding new columns.

The building was historically an electrical workshop and still contains the original equipment, such as a large gantry crane spanning the internal street.

“When I noticed that the point load of the gantry crane was 5 tons, I realised we could hang the entire building off the existing structure”, says Wolff.

The business incubation hub consists of a series of enclosed steel-framed glass “volumes” that run adjacent to the sides of the street and project into the central space, creating visual connections with the market and exhibition spaces below.

The low hung steel mezzanine floor, which forms the central exhibition space, appears to slightly step away from the massive steel braced columns, emphasising the notion that the floor is suspended “from the sky”.

Very little else in the space is actually permanent, Wolff says. The temporary parts of the fitout blur the lines between architecture and furniture.

On the west side of the building, large fixed 32m2 retail units of 7m in height create an edge to the street along which tenants can display their goods. These units are expressed in timber and slightly raised from the ground.

The smaller retail spaces in the central market are defined by movable 2.1m-high timber walls that double as cupboards. Timber trading carts of 2x2m2 form the smallest lettable spaces and can be pulled out and locked away.

The smallest scale is a 600mm x 600mm timber box, which can be used in various combinations to form displays and walls. Traders are given freedom to paint and change these boxes as they like.  These structures can be moved in order to change the spatial layouts when required.

Pine timber is used throughout for all furniture elements, beams and plywood flooring, explains Wolff, as it is a local, inexpensive and highly sustainable material.

Minimal interference

Wolff says one of the best ways to be resource-efficient and cost-effective is to “refuse to do something such as not installing an expensive technology, not demolishing something or not building something new when it’s not really needed”.

The choice was made to leave the industrial timber floor of the warehouse in its existing condition. The enclosed upper level buildings are all treated as interior spaces with efficient air-conditioning and quality thermal and acoustic materials, which make them comfortable.

A 100m-long skylight runs above the street in order to bring in natural light. Polycarbonate sheeting, which blocks out approximately 90% of the heat on the north side of the building, allows in ample light from above. The existing windows on the south side of the building were refurbished and the upper floor level was also glazed.

“We have achieved about 80% daylight autonomy on the upper floors,” says Wolff. Huge circular cut-outs in the low hanging slab above the market draw light into the space below.

Wind exposure at the open-ended entrances is reduced by carefully designed recessed walls that deflect the wind, and low scalloped walls that double as outside seating. Planted trees help to mitigate wind gusts.

The enclosed retail units are situated at the uncovered ends of the building to provide a buffer for the more exposed inside spaces. Large doors at each end can also be closed in order to provide extra shelter and security.

In keeping with the “outside market” concept, the space is naturally ventilated by being open at both ends. In order to deal with extreme temperature conditions, the smoke ventilators are fixed to temperature sensors so they open to allow heat to escape when the building is too hot, and close to retain heat when the building is cold.

Acoustically, the challenges included mitigating rain and wind noise, and footfall noise. These are only major problems for the enclosed spaces on the upper levels, and are mitigated by acoustic walls and ceilings, explains Terry Mackenzie Hoy, acoustic engineer from Mackenzie Hoy.

The huge suspended steel floor above the market space acts like a large acoustic panel by absorbing crowd noise from the market below and cushioning the footfall noise from above.

Experiences of the space

Wolff architects conducted intensive research into how markets and workspaces should be laid out in order to create an optimum environment for users. But the evidence comes from the tenants themselves. In general the traders are concerned about what the winter months will bring.

The comfort levels of an exterior environment will never be akin to those of an interior one, and Wolff says people need to adjust their expectations. However, the building will continue to be monitored environmentally and problems will be addressed as they arise.

The Watershed demonstrates a connection between the environmental and social aspects of space through simple responses to environmental issues and an iterative approach to adding solutions when required, without compromising on innovative and creative design.


By Mary Anne Constable

The full article appears in the August-September 2015 earthworks magazine.