NEC4 Option Z: How to Approach Additional Conditions | Gather

3 Feb 2026 · 62 min
1:01:38

The webinar, hosted by Glenn and featuring David Allen (SECA Southern) and Ben Walker (Gather), examined NEC4 Option Z – the additional conditions of contract that allow parties to tailor NEC contracts. The presenters explained why Z clauses exist, how they can be misused, and offered a structured approach to drafting them. They emphasized starting with a clear “why” – identifying a fault or gap in the standard contract – and then using flow‑charts to test the impact on processes, risk, and resources before drafting. Three informal categories of Z clauses were discussed: boiler‑plate/legal‑insurance clauses, constraints that lock out certain activities, and substantive changes that shift risk or governance. The speakers warned that poorly drafted Z clauses can create ambiguities, unintended consequences, and unfair risk allocation, often leading to higher tender prices, reduced supply‑chain participation, and strained client‑contractor relationships. They highlighted Abrahamson’s risk‑allocation principles (control, economic risk, gain/loss, planning efficiency, insurability) as a lens for deciding who should bear a risk. The balance between cost certainty and value for money was a recurring theme, especially when clauses attempt to shift design‑error risk onto contractors. Practical advice covered using existing NEC terminology, adhering to the NEC User Guide (plain language, active voice, short sentences), avoiding copy‑paste and legalese, and seeking internal and external (supply‑chain) review before finalising clauses. Real‑world examples illustrated pitfalls such as reducing compensation‑event notification periods, removing the mutual‑trust clause, and imposing blanket liability for pre‑contract document errors. The session concluded with a call to publish the rationale for any Z clause, engage the market early, and ensure that any additional conditions are coherent, transparent, and aligned with NEC’s collaborative spirit.

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