Key Takeaways

Follow Best Practice Before Drafting Any Z Clause

Before putting pen to paper, ask why the change is needed, what problem it solves, and whether the issue can be addressed through scope or contract data instead. Flowchart the change against existing NEC processes to catch conflicts and unintended consequences before they reach tender.

Share Your Reasoning With the Supply Chain

Publishing the thinking behind proposed amendments helps bidders price risk appropriately and builds trust. Contractors interpret unexplained changes as a signal that the client will be difficult to work with, which limits competition and increases tender prices.

Balance Cost Certainty Against Value for Money

Clauses that transfer all scope errors to the contractor may provide budget certainty, but they increase tender prices and can shrink the pool of willing bidders. Consider keeping contingency for errors and paying only when issues actually arise through the compensation mechanism.

Test Z Clauses Against Abrahamson Principles

Allocate risk to the party with most control, who can transfer the economic risk, stands to gain the most, or where the loss falls naturally. If reversing the positions would make you uncomfortable signing the contract, the clause probably needs rethinking.

Further Reading

GMH Planning’s own guidance notes, CECA bulletins and webinar pages on this topic. They explain the standard provisions and are useful alongside, not instead of, the executed contract.

Check the contract form, edition, incorporated amendments, main and secondary options, Contract Data and any Z clauses for your own project.

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