The cost of converting the London Olympic Stadium into a 54,000-capacity multi-use stadium is set to rise from £154m to £190m due to complications in installing the new roof.

Providing the support structures for the new roof have required significantly more strengthening work to the main roof truss than initially expected. The truss was originally designed to be taken down after the Games.

As a result, the London Legacy Development Corporation (LLDC) has allocated an extra £35.9m for the project, increasing the total cost for the conversion to £189.9m.

When complete, the roof will cover 45,000sq m and will be 84m at its deepest point, the longest cantilevered roof in the world, covering every seat in the stadium and improving the acoustics and spectator experience.

The work on the Populous-designed stadium is being undertaken by Balfour Beatty, which will be given the extra funding to complete the job. Balfour Beatty signed the £154m contract ($246.7m €195.1m) in January 2014.

The additional costs will be funded by project contingencies and additional income generated by LLDC from its other “developments”. West Ham United Football Club (WHUFC), which will be the stadium’s main tenant when it moves in to the venue in 2016, will not be asked to contribute towards the added costs.

Rod Sheard, who lead the Populous team of architects that designed the iconic stadium, told Sports Management: “The transformation is progressing very well and, when complete, will be a wonderful stadium.

“It will retain much of its recognisable charm from the London Olympics as well as its operational requirements for athletics and other field sports but also have the ability to be a fine football stadium for the West Ham supporters.”

The stadium will host five matches during the Rugby World Cup 2015 as well as the 2017 IAAF World Championships and 2017 IPC World Athletics Championships – the first time these global events have been staged in the same venue in the same year.