Double modal constructions (dmcs), the co-occurrence of two modal verbs within the same clause, are well-attested in English dialects of the Southern United States, as well as in African-American Vernacular English. dmcs pose a problem for generative grammar. Modals are traditionally viewed as tense-bearing items, only one of which may appear in a clause. Double modals challenge these restrictions. Several proposals have been put forth to account for dmcs within the theoretical framework of generative grammar. These proposals provide insight into the possible structures of double modal constructions. No work has looked at double modals from a functional perspective, however. This aims to fill that gap. Construction grammar has shown itself to be well-suited to phenomena that are non-predictable in either form or function. dmcs are clearly in this category, as respondents who do not use dmcs find them ungrammatical and their meaning at best unclear. Finding dmcs in traditional text corpuses is difficult due to their dialectal distribution and colloquial nature. Instances of double modals were gathered from the Corpus of Contemporary American English (COCA), and the relative usage of each was determined. The prevalence of certain double modal combinations (especially might could) and rarity of others is explained via degree of epistemic-deontic polysemy of the modals and whether they fill a semantic lacuna. The role of semantics in determining acceptable epistemic-deontic pairs bodes well for further analysis of double models within a construction grammar framework.