Milson Island Sports Hall by Allen Jack+Cottier

A steel shell curls over the arched frame of this sports hall near Sydney by Australian architects Allen Jack+Cottier.

Glazed end walls in the Milson Island Sports Hall allow views right through the building.

Milson Island Sports Hall by Allen Jack and Cottier

The inside is clad in curved, slotted plywood to absorb noise and withstand the impact of stray balls.

Strips of glazing run along both sides of the building below head height.

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Photography is by Nic Bailey of Allen Jack+Cottier.

The following information is from the architects:

Milson Island Sports Hall

The most recent addition to Allen Jack + Cottier's suite of award-winning sports and recreation centres for the NSW Department of Sport & Recreation is located just north of Sydney on Milson Island, in the Hawkesbury River.

The shape of the building emerged by morphing the ideal shapes resulting from the thermodynamic analysis, the side wind forces, the need to shed leaves and branches and yet collect water and the enclosure requirements. All building elements had to be sized to be barged across the river to the site.

The design celebrates this integrated thinking by not allowing any visible ridge, eaves gutters, downpipes or skylights on the exterior. The natural thermal ventilation aided by the suction caused by the wing shape demanded a clean crisp interior skin with no visible fixings bracing, wiring or lighting.

The acoustic slotted ply ceiling is integrated to the structural bracing, so that the walls and ceiling carry all the wind loads of 38 m of building to the ground. The shape of the building reduced wind load by 30%, thus reducing structural sizes and saving money.

At night, the curved wing shape of the new building acts as a proscenium arch to define the place for the campfire, an important part of each camp at the site. It works both for the audience inside looking out to the gathering space, and for the audience around the fireplace looking back into the hall.

When the campfire is lit at night, and the hall interior is illuminated only by a strip of lights, the building seems to magically float off the ground, into the surrounding bushland.

Natural light from the roof windows ground level slot windows and end walls create an even, almost art gallery like, light on the playing surface of the hall.

A combination of twelve wind turbines and a series of floor mounted louvres ensure the building remains cool in Sydney's fierce summer heat. In winter with the turbines and louvres closed a heat plume forms to act like an insulation blanket. Attached amenities and storage modules service the fireplace, the bushwalking activities and the oval so have to be accessed from outside, forming a strong entry and destination point.

Roof water, free from the blockage of leaves and branches, falls clear of the sloping glass slots into an oversized roof garden for natural filtering and collection to water tanks for future use.

This is a powerful building which in its frugality demonstrates the essence of shelter.