Contra proferentem is a rule of construction applying to written documents or deeds. The rule provides that if the wording of an agreement is ambiguous or uncertain, but not otherwise, the contract should be construed more strongly against the person whose words they are rather than the other party.
In the case of John Lee & Son (Grantham) Ltd v Railway Executive (1949) it was found that:
'We are presented with two alternative readings of this document and the reading which one should adopt is to be determined, amongst other things, by a consideration of the fact that the defendants put forward the document. They have put forward a clause which is by no means free from obscurity and have contended... that it has a remarkably, if not extravagantly, wide scope and I think that the rule contra proferentem should be applied’
If a party has incorporated its own standard terms and conditions of trade into an agreement then in the event of ambiguity those terms and conditions will be construed contra proferentem that party. Where however the parties execute standard form contracts, the contra proferentem rule will only operate in respect of amendments or additions to the contract.
Contra proferentem is a particularly important rule of construction in relation to exclusion clauses.
 Related articles on Designing Buildings Wiki
Featured articles and news
Green paper published for consultation.
Mental health issues effect 80% of construction workers. Read our interview with the founders of a new wellbeing initiative.
Would Stephenson be disappointed by the lack of progress on the high speed transport of Hyperloop?
The immersive pop-up cinema experience that could revolutionise on-site health and safety training.
5 out of 10 filtering facepieces fail HSE tests.
Eleven Magazine announce the winner and runners-up in their Moontopia competition.
As January is the time for hitting the gym, Designing Buildings Wiki lists the best gym architecture in the world.
London is at the top of the list of global construction megacities, beating Dubai and Abu Dhabi.
What are the innovative business models of the future, and how to incentivise supply chains to work on a whole life basis?