The 1 x 4.4 metre roof panel is the first of almost 10,000 panels to be fitted to the Stadium.
The roof will be split into two sections, a solid rear section and a translucent forward section. There will be 6,300 rear panels and 3,600 transparent polycarbonate panels at the front.
The initial lift comes after several weeks of preparation works.
Eight kilometres of cable net weighing 930 tonnes was lifted and connected over a four week period before 112 steel roof rafters, the longest of which is 38 metres, were lifted and secured into place.
Main contractor Balfour Beatty struck a deal last month with the London Legacy Development Corporation for an extra £36m for the conversion contract.
This has driven the original project cost up by nearly a quarter to close to £190m to convert the stadium into a new home for West Ham United.
Balfour was awarded the contract in January and is running against a fixed deadline to complete the first phase of the conversion to host games for the 2015 Rugby World Cup.
After the tournament Balfour will return to finish the conversion and create a permanent home for West Ham from 2016.
When complete the new roof will be twice the size of the original at around 45,000 square metres.
At 84 metres at its deepest point it will be the longest cantilevered roof of its type in the world and will cover every seat in the Stadium.
David Goldstone, Chief Executive of the London Legacy Development Corporation said: “Installing the first roof panel represents another significant milestone in the transformation of the Stadium into a world class multi-use venue.
“The overall spectator experience, whether that’s at a football match, concert or other sporting event, will improve significantly and the Stadium will become a great addition to Queen Elizabeth Olympic Park which is already proving to be a top destination for world-class events of all kinds.”
Karren Brady West Ham United Vice-Chairman said: “The roof is just one of the superb features that will make our new home one of the greatest stadiums in world football and a fitting legacy for the venue that did Britain so proud in 2012.”
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Facts about the Stadium roof
- At 45,000sq metres, the new roof will be twice the size of the original.
- At 84 metres at its deepest point it will be the longest cantilevered roof of its type in the world.
- The new roof will cover every seat in the Stadium.
- The design is intended to improve the acoustics and spectator experience for football matches, other sporting events and concerts.
- New floodlights will be installed that will reuse the light bulbs from the original Stadium lights.
- Work will be completed ahead of Rugby World Cup 2015.
- Eight kilometres of cable net ranging in width from 60 to 105 millimetres was lifted and connected over a four week period.
- The cable net weighs around 930 tonnes.
- There are 5,423 pieces of steel in the roof, weighing 3,900 tonnes.
- The longest roof rafters are 38 metres long and it will take 27 weeks to install all the steel.
- The roof panelling to the rear of the roof is an insulated system using a profiled lower deck with an insulation layer and covering for weather protection.
- The roof panelling to the front of the roof is formed of transparent polycarbonate corrugated sheeting.
- It will take 26 weeks to install the roof panelling.