Constructing the Ribbon Roof
The roof support frames consist of a 7 metre horizontal rafter 125mm x 25mm clamped between pairs of vertical members which are attached to each of the vertical laths in the gridshell.
Six longitudinal members 80mm x 12mm are let in to notches in the frame to support the ribbon roof, below each of these, the rafter is supported by a post with a simple lap joint at the top and a hemispherical turned base which is drilled for a bolt to be inserted and glued. This bolt then passes through the vertical lath on the gridshell and is secured with a stainless steel nut. The rafter is then supported at six points across the structure. The vertical member shown on the right of the following photo form the frames for the polycarbonate glazing.
Ribbon roof construction
The ribbon roof consists 100mm x 12mm longitudinal timbers laid at 200mm centres across the support frame, a waterproof reinforced polythene barrier backed with foil, then a multilayer insulation material is laid into a void, then a 12mm ply board and a further layer of 12mm ply which will be covered with Roofkrete.
Where the underside of the roof is outside the structure a plywood soffit replaces the 100×12 longitudinal members. The roof layers are clearly visible in the next picture.
Stages in the roof construction
The finished roof. Small section laths were fixed to the roof boards running diagonally from high to low points to distribute the run-off water to the sides of the roof. The whole was covered with three layers of 10mm galvanised mesh extending over the side of the roof and finishing with a metal bead at the soffit. The Roofkrete material was trowelled over the whole roof to cover the mesh layers.
The glazing consists of a upper vertical section and a lower sloping section that will cover the uppermost third of the gridshell. The polycarbonate glazing is mounted in aluminium extrusions fixed to the framing that supports the ribbon roof. At the base of the vertical section lead flashing has been fixed which will eventually overlap the lower glazing panels. The vertical sections have been fixed working from the scaffolding which protrudes through the gridshell, the lower sections will be fixed once the main scaffolding has been removed. Note the plastic filament strung underneath the roof as a deterrent to birds.
The bird deterrent consists of plastic coated stainless steel wires attached rigidly at one end and to a spring the other end.
With the completion of the cladding it is now possible to install the sloping glazing panels.
The glazing is almost completed, only the end sections remain to be finished.