VIDEO - London 2012's Olympic Stadium raises the roof

London's 2012 Olympic Stadium has reached another construction milestone as the cable net roof is lifted into place, ensuring the Stadium remains on target for completion by mid-2011.

The 450 tonne cable net, which took four weeks and 56 hydraulic jacks to lift, is formed between the outer, white steel roof truss and an inner tension ring 30 m above the field of play.

According to the Olympic Delivery Authority (ODA), over 900 tonnes of scaffolding and over 1 km of support platforms were used to assemble the 12000 m-plus of cables and walkways.

Commenting on the lift, ODA chairman John Armitt said, "It has been a complex engineering and construction challenge, complicated by the wind and rain in recent weeks [but] we remain firmly on track and will lift the lighting towers into place early next year, taking the Stadium to its full height.

Construction on the Olympic Stadium started in May 2008 and progress to date has included:

• over 4,500 reinforced concrete columns installed as the foundations
• 28 steel sections of the roof compression truss lifted into place - each weigh 85 tonnes and are 15m high by 30m long
• 112 steel rakers fixed to act as the terracing supports to hold the 55,000 seats in the upper tiers
• 12000 pre-cast concrete terracing units for the seating installed
• all five bridges and their abutments in place, connecting the Stadium island to the rest of the Park
• the fit-out of the 700 rooms and spaces within the Stadium, including changing rooms and toilets is progressing.

Next year, a 650 tonne crane will be assembled in the middle of the Stadium site to lift the 28 m-high lighting gantries on to inner ring of the cable net roof, taking them 60 m above the field of play.