Designs by HOK Sport do not include a roof, but may provide shelter for executive area

HOK Sport’s designs for the 2012 Olympic stadium do not include a roof structure, Building has learned.

An Olympic Delivery Authority (ODA) source said that the design did not have a roof, but that it gave the ODA the option of covering an executive or VIP area.

The source said: “Imagine if it was a wet summer – it would be a disaster. The ODA can’t make a decision at the moment, but there is an option for certain parts of the stadium to be covered.

“This obviously causes concern in relation to risk management in the construction programme, but the intention is to provide everybody with clarity to the situation as early as possible.”

The news emerged as Sir Robert McAlpine signed a memorandum of understanding with the ODA to deliver the £400m stadium after weeks of negotiation. The contractor forced the ODA to come up with the document after concerns over its non-Olympic workload and how it would manage its staff.

The source said: “The ODA realises McAlpine is its only feasible option to deliver the stadium. After much discussion it has given them a document. This is not the full contract with an agreed price, but a statement of intent to give them the works.”

The negotiations between the ODA and McAlpine for the full price for the stadium and surrounding works is continuing and subject to final designs that are yet to be released. However it is understood that negotiations are based around a programme of incentives to complete the stadium early and the contract may be on a cost plus basis.

Last week, the government said that the Olympic budget was £9.3bn with the construction budget set at £5.1bn, including a contingency of 20%.

In other Olympic developments, architectural heavyweights Lord Foster and Sir Michael Hopkins have said they will bid to design the international media centre for the Olympics. They will be joined by Sheppard Robson and BDP. Other contenders, Broadway Malyan and Hamilton Associates, have ruled themselves out, saying they will not go for any main venues but will focus on projects peripheral to the Games.

The ODA has also put the aquatics centre for the 2012 Olympics out to tender for contractors.

Work clearing and excavating the site has already begun and construction is due to start in 2008.

Meanwhile, headhunters are expected to draw up a shortlist of candidates for the position of ODA chairman within the next week. Contenders include Roy McNulty, the acting chair; Peter Rogers of Stanhope; and Sir Stuart Lipton, the former Stanhope boss.