Architect Allies and Morrison’s £71m fit-out of the Royal Festival Hall on London’s South Bank has risen £20m in cost and been delayed for six months.

The South Bank Board, which controls the redevelopment of the cultural complex, has confirmed a final price estimate with contractor ISG InteriorExterior of £91m. This includes the cost of the removal of asbestos and solutions to structural problems.

Because of the problems, the board has had to move the opening of the newly refurbished Royal Festival Hall back from January to the middle of June 2007, causing the cancellation of a number of concerts scheduled in spring 2007.

A spokesperson for the South Bank Centre said the initial cost estimate had never been completely finalised.

The spokesperson said: “The South Bank Centre has now confirmed details of the contract with ISG InteriorExterior, giving the maximum certainty on total cost and timetable for the major refurbishment of the Royal Festival Hall’s foyers, auditorium and infrastructure at £91m.”

The spokesperson added that the figure included additional landscaping on level one and the terrace and the refurbishment of the exterior on the riverfront.

The spokesperson said: “The reasons for the increased price are the significant inflation in building costs in London and the South-east; the complexities of safe removal of asbestos from a 54-year-old building; and structural changes to a grade I-listed building proving more complex than anticipated.”