The LinGO Grammar Matrix (Bender et al. 2002, 2010) provides a system for user-linguists to jump start the creation of starter Head-driven Phrase Structure Grammar precision grammars (Pollard and Sag 1994), with semantic representations in Minimal Recursion Semantics (Copestake et al. 2005). The Grammar Matrix provides an online questionnaire for users to describe their target language in a user-friendly and typologically motivated fashion. This description is utilized to produce customized, language-specific rule definitions extending a core, near universal set of types available to any grammar. I propose and implement a new library for intersective adjectives cross-linguistically, considering both attributive and predicative constructions, editing and extending the core grammar while adding additional capabilities to the online customization system to analyze adjectives in target languages and generate language-specific customized grammars with analyses of adjectives. I present a broad typological review the behavior of adjectives, including the morphology and syntax of adjectives, along with an overview of the literature on the semantics of adjectives. I also present a review of the adjectives in several large implemented deep linguistic HPSG grammars in the DELPH-IN formalism. I develop a cross-linguistic analysis of adjectives, adapting previous DELPH-IN analyses to cover significant amounts of new data. The analysis relies not only on definitions in the lexicon, but also on defining the syntactic behavior of adjectives in the morphology. I present a computational implementation of this analysis as an extension to the Grammar Matrix. Finally, I present an evaluation of this extension, showing that the extension achieves 100% coverage of development language test suites and 100% coverage of held out test language test suites, with minimal spurious ambiguity.