This paper proposes a novel modular building system using curved-crease origami columns. The column is designed with a non-rotationally symmetric trapezoidal cross-section profile and an elastica curvature surface profile. The selected profile and surface curvature allows for flexible tessellation and interlocking of adjacent columns, forming intricate, quasi-continuous wall surfaces using a single repeating component. A generative shape grammar is developed for parametric wall surface description and validated against desktop-scale prototypes. A building-scale prototype is also constructed from cardboard material, showcasing the use of integrated digital design and fabrication techniques for the rapid construction of ultra-lightweight curved-crease origami building systems.