The Marlowe Academy in the UK is an award-winning school building designed by Building Design Partnership Ltd. (BDP), with the entire structure placed under a single roof and featuring a long span engineered timber grid shell. The teaching spaces are connected by a theatre in the centre, providing heart space – a key element in the architectural vision for this project.
The heart space is at the centre of an arc of teaching, sports and performance accommodation with the double curved timber grid shell roof uniting all these internal spaces. The grid shell is a section of a toroid, which provides a structurally efficient and elegant enclosure to the column-free space below.
The grid shell climbs 28 metres to the roof of the teaching faculty at the perimeter of the central space. The tight radius of the inner support is converted to a wider radius on the outer support by the clever use of parabolic plan geometry.
Ribs measuring 300mm deep are formed from 75mm-thick Kerto LVL (laminated veneer lumber) to a maximum of 3 metres between nodes. The roof deck, also formed from LVL, is used as a stressed skin where the forces within the shell require it.
The graceful link between the grid shell roof and the adjoining sports hall and performance hall roofs further enhances the clarity of the form.
The shell based structural form in timber used at the academy spans 22m x 68m in girth, yet the ribs are only 30mm deep, and is probably best described as 'geodesic'. It took less than 600 ribs to cover 1000m², generally under 3 metres long, with many repeat patterns making them easier to process on and off site.
The ribs were profile cut from Kerto LVL (mostly spruce), which was also used for the deck. This was bent around the 10m and 30m radii detailed across the roof section. A dense pattern of ledgerlok screws secured the 33mm sheets to act compositely with the ribs, thus adjusting the remarkable span to depth ratio.
The joints made extensive use of Cowley Connectors, epoxy bonded into the rib ends to secure the ribs to the nodes.
Image: All images courtesy UK Wood Awards [Sourced by arrangement from timber+DESIGN magazine (www.timberdesignmag.com)]