Master the practical benefit rule in contract modification.
Williams v. Roffey Bros. [1991] 1 Q.B. 1 (C.A.)
Roffey Bros. hired Williams as a subcontractor to do carpentry work on flats. Williams underpriced the job and was struggling financially. Concerned about delay penalties, Roffey promised Williams an additional £575 per flat if he completed on time. Williams continued work but Roffey refused to pay the additional sum. Williams sued for the extra payment.
Can a promise to pay more for work already contractually owed constitute valid consideration if the promisor receives a practical benefit?
When a party to an existing contract promises additional payment in return for the other party's promise to perform their existing contractual obligations, that promise is supported by consideration if the promisor obtains a practical benefit or obviates a disbenefit, provided there was no duress.
The court held that Roffey's promise to pay extra was enforceable because Roffey received practical benefits: avoiding delay penalties, avoiding finding a new subcontractor, and ensuring timely completion.
This case modified traditional consideration doctrine by recognizing practical benefits as sufficient consideration. It provides an alternative to the pre-existing duty rule and represents a modern, pragmatic approach to contract modification.