Extrudable building material wall structure and method

A wall structure and a method for forming a wall structure is provided using three-dimensional printing of extruded building material applied to a surface of a building structure. According to one embodiment, the wall structure includes a pair of outer wythes spaced from an inner wythe. The outer wythes can include a core extending between the pair of outer wythes and toward the inner wythe. A protrusion can also extend toward the inner wythe a spaced distance from the inner wythe or entirely toward and adjoining the inner wythe. The core is configured with an inwardly facing spaced opposed surfaces of the outer wythes surrounding a vertically extending rebar, with grout surrounding that rebar. Horizontally extending support pins can be spaced parallel from each other and extend from the protrusions and into the inner wythe.