If a defect has been notified by the Project manager and the contractor and Project manager agree a method of fixing the defect but the method involves the employers designer in additional design work which they charge the employer for can the employer claim this cost back from the contractor
There is no mechanism for this in the contract, the Employer’s rights in respect of Defects are limited to recovering the cost of other people correcting a Defect:
if the Contractor fails to do so within its defect correction period (45.1) or
if the Contractor is not given access to correct a Defect before the defects date (45.2)
Alternatively the Contractor and Project Manager may agree that a Defect does not have to be corrected. In this case the Contractor submits a quotation for reduced prices and when the Project Manager accepts the quotation the Works Information etc are changed accordingly (44.2).
In your situation if the Works Information was changed this should trigger a CE. However, the PM may decide that the reason it was changed was the Contractor’s fault i.e. because the Defect was caused by some failure of the Contractor, in which case the PM would say “no” to the CE.
From what I can see, correcting a Defect shouldn’t require additional design work - if the work is in accordance with the WI then no further design work should be required.
What you have agreed in this case appears to me to be doing something different from what was in the WI, in order to ensure that the Defect can be accepted. That implies a situation as set out in Clause 44 - although some corrective work is being done, the Defect as such is being accepted. In that case, the Contractor should submit a quotation for reduced Prices, and that quotation would take into account the cost incurred by the Employer in the additional design work.