Construction work runs on standard forms of contract, often heavily amended. Knowing which form you are on, and where the traps usually hide, can be the difference between a profitable job and a painful one. Here is a plain-English tour.

The common families

  • JCT (Joint Contracts Tribunal): the most widely used family in building work, with sub-contract versions such as the design and build sub-contract. Familiar and broadly balanced, but frequently amended.
  • NEC (currently NEC4): process-driven and collaborative, built around early warnings and a live programme. Its Z clauses are bespoke amendments added by the client, and this is where onerous terms usually appear.
  • Bespoke and amended forms: many main contractors issue their own sub-contract, or a standard form with a long schedule of amendments. Always read the amendments, not just the base form.

Areas to look out for

  • Payment terms. When is the due date and the final date for payment? Watch "pay-when-certified" or back-to-back terms that tie your payment to someone else being paid.
  • Z clauses and amendments. Read every one. They commonly shift risk, lengthen payment, or cut your rights.
  • Insurance. Check what cover you must carry (public liability, employer's liability, and professional indemnity if you design) and who insures the works themselves under a contractors' all-risks policy.
  • Retention. The percentage held and when each half is released, see retentions in construction.
  • Liquidated damages. What you pay per week for delay, and whether the figure is realistic.
  • Variations and programme. How changes are valued and how time is managed.
  • Collateral warranties, indemnities and set-off. Open-ended indemnities and wide set-off rights can be costly.

Read it before you sign

Most disputes trace back to a clause someone did not read. Take the time, or take advice, before committing, particularly on the amendments and Z clauses where the real risk lives.

This is general information, not legal advice. For a specific contract, take professional advice before signing.