The paper argues that interlocutors in intercultural interactions rely mainly on co-constructed temporary norms rather than on codified norms of the target language. There is a complex interplay of codified and emergent norms that drives interaction. Temporary norms emerge through temporary communicative extension of the system (TCE) that are expressions, chunks and utterances that violate the existing relatively definable norms and conventions of target language use, but still make sense in actual situational contexts and can be considered possible outputs of (...) the English language system. TCEs function as building blocks for temporary norms, and they can also be building blocks in common ground development. The paper demonstrates these functions through examples in intercultural interactions. (shrink)