Plantation Place Galleria
Plantation Place, London
Engineer: Arup Associates
2000-2002

The Galleria, just west of the tower of London, will make a new pedestrian connection through the Plantation Place office development by architects Arup Associates, that will open up views of the spire of Christopher Wren's church of St. Margaret Pattens. The roof uses the compressive strength of the glass in its surface to create an extremely transparent glass vault allowing the clearest possible view of the spire.

Light from the sky is reflected down into the narrow tapered space from reflectors positioned on the building directly to the north of the Galleria. The translucent south wall is a semi-reflective and translucent surface on which light and shadows play throughout the day, and highly reflective vertical blades between the semi-reflective panels catch the light of the sky behind the viewer creating bright lines that draw the eye up to the spire.

The roof rests on steel brackets on the main building on the north side, and on the 14m high glass wall on the south side.
The shape of the roof is based on a translational geometry to accommodate the tapered plan, creating a double curved surface whose single panels are still planar though not exactly of equal size.

The overall design intent was to create an all-glass roof that is extremely transparent with a minimized number of structural elements.  To achieve this we  used the glass as the primary structural element, forming a compression vault.

To stabilize the roof we developed several different options of using tension rods.
At the first planning stage we decided to use a radial cable arrangement at about 3m spacing, together with a small rib on the outside of the glass, to stabilize the roof under asymmetrical loads.  In the further planning process we changed this design to a  layout where the cables connect the glass panels directly, going to every third panel.  This arrangement proved to be sufficiently stiff in computer load simulations that we could avoid using the rib, achieving a remarkably transparent glass roof.

James Carpenter, Luke Lowings and Valerie Spalding worked on this project from concept design to design development, at both JCDA and Carpenter/Lowings Architecture & Design.