The Joist Jak is a self levelling, adjustable pedestal for use on raised trafficable surfaces supported on Joists. The Joist Jak accepts joists up to 50mm between the two support flanges and will support loads up to 2400 kg. With a smooth moulded base for sitting on waterproofing membranes, the Joist Jak allows a fast and simple way to construct a timber type deck on waterproof balconys or roof tops. Height adjustable from 20mm to 25mm.