The British Museum has been told to pay Easton Masonry (Portland) Ltd an extra £211,904.24 for the new south portico in the Great Court project that is built in French limestone rather than British Portland stone.

The museum has been awarded additional costs of £137,116.30 against Easton Masonry.

Although the £97million Great Court development was successfully completed on time and on budget in 2000, it had proved impossible to resolve a number of outstanding disputes between the Museum and Easton Masonry, with Easton maintaining they fulfilled the contract to build the portico of "Portland or similar" as specified, in fact using Anstrude Roche Claire.

The disputes were, therefore, finally referred to an adjudicator, who heard the two sides' arguments in London in July (click link above to view previous articles).

The adjudicator has now confirmed that Easton were in breach of contract and misled the Museum's design team by supplying Anstrude Roche Claire for approval as Portland stone.

He has also concluded that the Museum acted properly in mitigating its losses by allowing construction to proceed in Anstrude Roche Claire stone once it became aware that Anstrude was being used.

The Museum says it was advised that it would have cost £3million in delays to the overall project to have terminated Easton's £1.73million contract.

The adjudicator's decision, and the award of additional costs of £137,116.30 to the Museum, has cleared the way for decisions in relation to the remaining disputes with Easton, resulting in additional payments to the contractors of £211,904.24.

A spokesman for the Museum said: "We are pleased this matter has been concluded. The adjudicator's findings support the Museum's stance in relation to Easton Masonry's breach of contract and its conclusion when the stone substitution came to light that, however regrettably, it was not realistic to terminate the contract with Easton and find a new contractor to build in Portland stone."

The award to the British Museum was based on a series of calculations covering the additional costs for reports incurred by the museum as a result of the stone not being Portland.

The award to Easton Masonry was calculated on the basis of 37 weeks of delay that led to factory downtime and factory overtime, additional site overheads and revised logistics.