Mr. Phelim Devine:

You can nail down the cost because, when you specify a sink, the contractor prices for that in the bill of quantities or pricing document. However, when it is incorporated into the works, there may be something missed, the alignment might require an extra bit of mastic, or the bulkhead might have to be built out further. The costing will be for a certain number of kilometres of bulkhead or plasterboard, but there might be an extra bit of plasterboard required. The contractor is entitled to seek the amount of the additional cost because it is a re-measurement contract.