A turf-roofed canopy supported by tapered glulam beams and columns
The canopy consists of a 145 x 45mm tongued-and-grooved timber deck with a two-layer turf roof system supported by eight 450 x 135mm tapered glulam beams.
To minimise the number of columns required and to present a clean, uncluttered soffit, the glulam beams are suspended from 203 x 203mm UB beams which run above the deck. The beams are drilled through to receive pairs of M12 dome-headed bolts which run through them and are fixed to recessed 280 x 40mm stainless steel plates in the glulam soffits.
At the front of the canopy the steel beams are supported by two tapered glulam columns with pinned and forked connectors; a drum rooflight is set at their connection with the steel beam above, making the structural logic visible.
At the rear, five beams rest on a wall plate, and a 254 x 254mm UC spreader beam - to ensure lateral stability - is bolted to the top of the ticket office wall.
The three adjacent beams are suspended from a 203 x 203mm UC which is supported at one side by a SHS column concealed in the ticket office wall (now clad with limestone), and at the other side by a tapered column hard against the cafe wall.
To accommodate the anticipated severe snow load on the canopy above the entrance passage to the caves, glulam beam sizes have been increased to 185 x 450mm and the UB beam supports are doubled. At one side the double beams rest on a small glulam column; on the other side they rest on a 450mm high concrete base secured to a rock ledge by a pair of 1.5m deep rock anchors.