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AJ Specification Live: Roofing

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Industry professionals came together to discuss and explore roofing at this month’s AJ Specification live seminar

Specification manager Daniel Weait from the sponsor, MarleyEternit, introduced the event on the topic of roofing and drainage, echoing the February print issue.

David Kirkland, founding principal of Berkhamsted-based Kirkland Fraser Moor, discussed the practice’s Quintain House project which uses one of MarleyEternit’s products.

The home is roofed in double-curvature cut hip tiles, designed with Rhino software, with Grasshopper plug-in.

Acting AJ Specification editor Felix Mara said the roof reminded him of Alec Clifton-Taylor’s description of billowing eiderdowns of terracotta red in The Pattern of English Building - but that Kirkland had achieved this effect by design rather than by accident.

Quintain house by kirkland fraser moor exterior

Quintain house by Kirkland Fraser Moor

Foster + Partners’ Paul Kalkhoven’s theme was ‘2x light + 1x heavy’. The head of the AJ100 practice’s technical development spoke about two lightweight roofs: the stainless steel canopy at Marseille Harbour with 5m cantilevers terminating in 15mm radius edges, and the 10m span roof of the Zorlu Apple Store in Istanbul, supported entirely by glass perimeter walls and designed with Eckersley O’Callaghan.

By way of contrast, Kalkhoven explained that the practices Ciudad Casa de Gobierno in Buenos Aires featured a concrete roof, its wave profile gently falling 4m from peak to trough, supported on circular columns at 24m intervals. A pattern of fine grooves raked into the concrete soffit softens the acoustics.

Acoustics was centre stage in the projects presented by Jason Flanagan. The Flanagan Lawrence design director discussed his RIBA Award winning lightweight Soundforms music pavilion concept, which delivers booming outdoor acoustics without the need for audio amplifiers. Flanagan also discussed the refurbishment of an outdoor theatre in Szczecin, Poland, with an arched roof made from inflatable panels.

Flanagan Lawrence CAM 06 PRINT

Flanagan Lawrence CAM 06 PRINT

In the Q&A session, Felix Mara asked the speakers for their thoughts on ways to design and execute elegant roof structures without compromising technical requirements such as drainage and thermal insulation, as well as complying with building regulations. Paul Kalkhoven noted that a project’s geographical location was a major influence. Jason Flanagan agreed that one’s choice of materials also had a big impact, such as the various benefits of ETFE versus glass.

Adam Knight, director at Hugh Broughton Architects, spoke about the challenges of designing and installing a new ETFE canopy over the central courtyard at Congress House, the TUC headquarters in central London. He noted that ETFE has been around since the 80s and has therefore been proved by the test of time.

In the concluding discussion the speakers, including David Kirkland who worked on Grimshaw’s Eden Project, further discussed the pros and cons of ETFE roofing. On the negative side, it can be noisy when it rains and can attract birds, but positively it is 1% the weight of glass and therefore does not require a heavy support structure, lending itself to larger module sizes with less restriction on the width of fitting. ETFE also provides better thermal insulation than glass.

Bringing the evening full circle Felix Mara concluded with the observation that David Kirkland had demonstrated at Quintain House that complex roof curvatures are not only possible with membrane and sheet materials such as ETFE.

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