This paper discusses root phenomena in imperative clauses, assuming as diagnostics conversational dynamics and the type of discourse categories that are admitted in their C‐domain, through a systematic comparative interface investigation in three languages (English, Italian and Spanish) based on an original experimental work. This novel perspective sheds new light on the syntax‐semantics mapping and the interface (syntax‐prosody) properties of imperative clauses, embedding the relevant proposal in a cartographic framework of analysis. Based on a twofold distinction of root phenomena – those which are widely allowed in Common Ground‐active (Type I) contexts and those which can occur in non‐Common Ground‐active contexts (Type II) – it is proposed that imperatives are non‐Common Ground‐active propositions with no update potential, thus allowing only Type II root phenomena. Syntactically, imperative clauses are dominated by a super‐ordinate Speech Act Phrase, including the Speaker and the Addressee as co‐arguments, which explains the blocking effects identified in imperatives.