[WORKING DETAIL 16.07.09] Bull nose detail, Snowdon Summit Visitor Centre by Ray Hole Architects
Snowdon Summit Visitor Centre − The bull nose needed to maintain a flexible weathertight seal between wall and roof, while supporting the significant dead loads applied by the granite, snow and ice in conditions where winds speeds can reach 150mph and humidity levels can approach 100 per cent.
The bull nose is a large, half-round section of curved granite inspired by locally quarried curling stones. It is supported by a standard stainless-steel bracket system, specially developed with Halfen to suit the 3D geometry. The whole assembly is cantilevered from the primary structure on large galvanised steel fins, which provide sufficient depth to house the roller-shutter drive systems designed by HAG. The shutters are necessary to protect the glazing during winter shutdown, but the blades are perforated so that they can also act as a solar shade.
The roof consists of an outer skin of granite planks, supported on a stainless-steel rail system secured to the seams of the aluminium standing seam roof using clips. The roof was developed by Corus using its Hi-Point system, which allowed bays of the roof to be prefabricated, complete with insulation liner and frame. Given the unpredictable weather conditions, a prefabricated system was considered safer to install than individual sheets, and it also significantly reduced the installation time.
The waterproofing between wall and roof uses a thick Prelasti membrane, carefully located away from the perimeter to minimise the number of penetrations through it.
Garry Reynolds, director, Ray Hole Architects