A construction system for constructing a structure atop a foundation , the construction system comprising: a rail assembly , forming a track, wherein the rail assembly is configured to be mounted to the foundation , wherein the rail assembly comprises a first elongate rack comprising a plurality of axially adjacent teeth ; a gantry movably disposed on the rail assembly , wherein the gantry is configured to translate along a first axis relative to the rail assembly , wherein the gantry comprises a first driver configured to rotate a pinion gear that is engaged with the teeth of the first elongate rack to translate the gantry (50, 350 450) along the first axis relative to the rail assembly ; and a printing assembly movably disposed on the gantry , wherein the printing assembly is configured to translate along a second axis relative to the gantry , wherein the second axis is orthogonal to the first axis ; and wherein the printing assembly is configured to deposit vertically stacked layers of an extrudable building material onto a top surface of the foundation to construct a structure , wherein the gantry comprises: a vertical support assembly movably coupled to the rail assembly with a plurality of rollers engaged with a track defined by the rail assembly ; and a trolley bridge assembly movably coupled to the vertical support assembly such that the trolley bridge assembly is configured to translate along a third axis relative to the vertical support assembly ; wherein the third axis is orthogonal to each of the first axis and the second axis ; and wherein the printing assembly is movably coupled to the trolley bridge assembly . a rail assembly , forming a track, wherein the rail assembly is configured to be mounted to the foundation , wherein the rail assembly comprises a first elongate rack comprising a plurality of axially adjacent teeth ; a gantry movably disposed on the rail assembly , wherein the gantry is configured to translate along a first axis relative to the rail assembly , wherein the gantry comprises a first driver configured to rotate a pinion gear that is engaged with the teeth of the first elongate rack to translate the gantry (50, 350 450) along the first axis relative to the rail assembly ; and a printing assembly movably disposed on the gantry , wherein the printing assembly is configured to translate along a second axis relative to the gantry , wherein the second axis is orthogonal to the first axis ; and wherein the printing assembly is configured to deposit vertically stacked layers of an extrudable building material onto a top surface of the foundation to construct a structure , wherein the gantry comprises: a vertical support assembly movably coupled to the rail assembly with a plurality of rollers engaged with a track defined by the rail assembly ; and a trolley bridge assembly movably coupled to the vertical support assembly such that the trolley bridge assembly is configured to translate along a third axis relative to the vertical support assembly ; wherein the third axis is orthogonal to each of the first axis and the second axis ; and wherein the printing assembly is movably coupled to the trolley bridge assembly . <EOS>