Architect Grimshaw has been dealt a blow in the Bath Spa saga after the local council’s internal report suggested that the latest disaster to befall the project could be caused by design problems, writes George Hay.

Bath and North-East Somerset council (BANES) commissioned the report to find out why the shower room floors were leaking.

A spokesperson from Mowlem, the project contractor, said the report confirmed the view that “the problems in the waterproofing to the flooring related to Grimshaw’s design and specification and were not a workmanship issue”.

The spokesperson said the report cleared Mowlem of any errors in the construction of the waterproof floor. He said: “We are in receipt of an independent expert report – produced at BANES’ request by architect Bickerdike Allen and materials specialist Stats – which effectively audits Grimshaw’s design and reflects on its instruction to Mowlem in respect of the waterproofing problems to all the flooring in the Bath Spa.”

In a statement to Building, Mowlem quoted the report’s findings. This confirmed their view that: “There is an inherent lack of clarity in the original design which, irrespective of the consideration of the fundamental suitability of the RIW membranes for the specific use, make an instruction simply to repeat the work properly in accordance with the design, an unrealistic request.

“Unless Grimshaw does have evidence of satisfactory long-term performance of Toughseal or Toughseal in combination with RIW Flexiseal in comparable circumstances, there will be no basis for their contention that the design is adequate.”

Nicole O’Flaherty, responsible for regeneration at BANES, confirmed the council had commissioned the report but said that it was for Mowlem and Grimshaw to resolve the leaking problems.

There is an inherent lack of clarity in the original design

Internal report (as quoted by Mowlem)

She said: “The report was forwarded to both Grimshaw and Mowlem to help resolve the issue. It is up to Grimshaw to come up with a further instruction. At the moment we are in limbo.”

BANES would not comment on whether it would be seeking compensation from Grimshaw but denied it would seek a new architect. It also admitted that it could not give any estimate for how much more the £36m project would cost.

The council would not reveal whether it would be suing Grimshaw.

Grimshaw declined to comment.