This would be a matter for the designer's professional indemnity insurance, your Client would have to prove that the Consultant had not used the skill and care normally used by professionals providing similar services.
Also the Client's Scope will be relevant in terms of what standards / specifications should the Consultant design in accordance with? This said, the Client's only remedy for defective service is for the Consultant to correct it, i.e. if they hadn't designed in accordance with a specification that required a drip then the design should be re-issued however the cost of doing so would still most likely be part of Time Charge. Remember Option C involves the Client sharing some risk with the Consultant.
Just an observation but surely discrepancy in brickwork alignment is the Contractor's Defect under the ECC and not a Consultant one under the PSC?
Also the Client's Scope will be relevant in terms of what standards / specifications should the Consultant design in accordance with? This said, the Client's only remedy for defective service is for the Consultant to correct it, i.e. if they hadn't designed in accordance with a specification that required a drip then the design should be re-issued however the cost of doing so would still most likely be part of Time Charge. Remember Option C involves the Client sharing some risk with the Consultant.
Just an observation but surely discrepancy in brickwork alignment is the Contractor's Defect under the ECC and not a Consultant one under the PSC?