PROJECTS
A series of LVL trusses form the central spine ; they are set on the diagonal and rise to the ridge .
All the trusses taper to reflect the magnitude and orientation of the forces acting on them – any portion that is superfluous has been removed . Analysis of the stresses caused by wind load ( sideways ) and snow and dead load ( vertically ) indicate where the timber could be optimised . The 7.5m long cantilever roof trusses taper as the bending forces reduce towards the cantilever tip , through the column to the pin connection at the ground , and at the central node above the spine . The ends of the top and bottom flanges become solid as the shear force increases along the section . The node is a key component of the structure , the point where vertical loads from the roof are transferred to the 3.1m high columns below . The node also acts as a portal frame haunch to provide the rigidity required to resist the horizontal wind forces which act across the structure .
The use of LVL creates a sophisticated piece of engineering , strong and lightweight , yet with all the warm tones and domestic qualities that timber provides . The trusses were produced from Kerto LVL provided by Metsä Wood ; 3mm thick , rotary-cut sustainable Nordic spruce veneers bonded to form a continuous board and cut to suit the required basic shape . These were transported to the factory of timber specialist Blumer-Lehmann in Switzerland where they were CNC cut to form the series of tapered layers which make up each truss . “ By studying the process ,” explains Darron Haylock , project architect . “ We were able to maximise opportunities to refine it .”
For instance , although all the LVL layers which make up a single tapered truss follow a consistent perimeter profile , two inner layers were specially cut to create the two sets of diagonal web flanges ; all the layers were then dowelled and glued together to form the final truss . Likewise , the LVL layers of the truss columns and the cantilevered beams were extended at the ends to create the triangular node ; during construction the column layer of the node slots between the cantilever truss layers of the node , in a manner similar to a halved timber joint .
All fixings between the trusses are concealed ; a metal Y-shaped strap along the top of each cantilever truss connects it to the diagonal roof trusses .
SUSTAINABILITY
The desire to create a homely environment , in contrast to the institutional space of a clinic , defined the approach to the building environmental design ; natural ventilation , daylight and radiant floors provide a comfortable environment within a low-energy building . Passive design elements , such as the deep roof overhang , help to shade the building from excessive solar gain during the summer and capture the low winter sun – therefore minimising energy consumption . The sustainability of the building in use was also considered , with water efficient fixtures , waste separation and a greenhouse .
// FEB / MARCH 2017 37