Extension & Renovation Contracts: The Checklist

Nearly every homeowner dispute we run traces to the same origin: a big project on a small document. The extension contract checklist below is not bureaucracy — it is the distilled autopsy of hundreds of building disputes, reduced to the terms that would have prevented them.

The Checklist

• Parties and scope: full legal names (is it him or his company?), and the works defined by reference to drawings and a written specification — the reference point every later argument returns to;
• Price basis: fixed price, or estimate with defined mechanics? What is included, excluded, and provisional? Ambiguity here is where bills mushroom;
• Stage payments behind the work: verifiable milestones, paid after completion of each — never ahead — with a 5–10% retention until snags clear;
• Variations in writing: scope and price confirmed before the change is built — the single most dispute-preventing clause in domestic construction;
• Timeline: start, substantial completion, and what happens on serious delay — even a simple written expectation changes later conversations;
• Insurance and compliance: public liability sighted, responsibilities for building control confirmed for works of your type;
• Snagging and defects: the inspection-remedy-retention-release sequence written down;
• Disputes: a sensible escalation term — discussion, then mediation — beats silence.

Why Payments-Behind-Work Is the Master Principle

Run the test at every stage: if the builder vanished tomorrow, would the work done exceed the money paid? Keep the answer yes and almost nothing that goes wrong can ruin you — the abandoned-job playbook becomes an inconvenience instead of a catastrophe. Let the answer drift to no and every other clause is decoration. Deposits modest and purposeful; materials paid on vouched invoices; retention held to the end.

Getting It Signed Without a Standoff

Good builders sign reasonable documents — many will respect you more for asking. Frame it as mutual protection (it genuinely is: written variations protect his extras claims too), keep it short, and treat refusal to write down basics as the free information it is. For larger projects, or any contract the builder supplies, a fixed-scope legal review before signature is the cheapest insurance in the job: contracts review. And if you are reading this checklist mid-dispute rather than pre-signature — the toolkit for that lives at disputes with builders, and the 2022 Act protects you regardless of paperwork.