This article takes a usage-based Construction Morphology perspective to examine the polysemy of the locative prefixoid up in complex words such as upstairs, upland, upheaval and uproot. Drawing on a relational structure model of morphosemantics, it is argued that the prefixoid systematically approximates the functions of different syntactic categories in different complex words: up functions like a preposition (upstairs), adjective (upland), adverb (upheaval) and verb (uproot). These constructions consequently require bases of specific syntactic categories and differ in the ways in which the prefixoid semantically relates to the second element. These subschemas are investigated in detail using corpus data from the BNC, collostructional analysis and various productivity measures to analyze the selectional restrictions of the open slot of the constructions as well as the semantics of the complex words. This approach elegantly solves the question of category change and the difficulties in identifying the syntactic category of the base in complex words with locative prefixoids, providing an alternative to the righthand head rule.