The council has now called in contractors to demolish part of the 310-pupil zero carbon school built three years ago.
Temporary classrooms have now been installed while repairs are carried out to other buildings.
The claim is being made to cover the costs of rebuilding and mobile classrooms being put on a neighbouring site until the work is complete in 2016.
Temporary classrooms being installed
A report commissioned by the council last year said the building started letting in water shortly after it was finished and that significant repairs were needed.
It highlighted “complexities within the rainwater harvesting system” and “concern with the specified use of materials”.
In a statement the council said: “We’ve issued letters of intent to the architects and contractors amounting to over £7m.
“That covers the cost of the construction work and the cost of temporarily relocating the school, including the temporary classrooms.”
Both Interserve and White Design said they would not comment while the project was subject to legal proceedings.
