JCT Contract

JCT contract families

JCT publishes around 20 contract types covering different project structures. The most common: Standard Building Contract (SBC) for traditional procurement; Design and Build (DB) for contractor-led design; Intermediate Building Contract (IBC) for medium-complexity projects; Minor Works Building Contract (MWBC) for small jobs.

Each contract has variants (with quantities, without quantities, with approximate quantities) reflecting how the works are priced.

Variations under JCT

JCT variations are simpler than NEC compensation events. The architect or contract administrator issues a written instruction; the contractor prices it; the consultant agrees the price; the variation is approved and added to the contract sum. The audit trail is the instruction itself plus the agreed quotation.

JCT does not have NEC's mandatory early warning system. Variations are reactive rather than predictive. This makes JCT lighter-touch but also means cost surprises are more common.

Common pitfalls

• Verbal instructions becoming variations. Under JCT, instructions must be in writing (or confirmed in writing within 7 days). Site verbal instructions are a common dispute source.
• Provisional sums not properly de-converted. JCT projects with provisional sums need them resolved before final account; consultants who let provisional sums drift accumulate huge final-account disputes.
• Treating JCT as NEC-light. The contractual obligations are different. Under NEC, the contractor has a duty to programme; under JCT, that's typically not the case. Project controls patterns differ accordingly.

Related

• What is an NEC contract? →
• What is a variation? →
• Variation management module →