An ultimate strength theory is developed for double chord rectangular hollow section (RHS) K-joints that accounts for both perfectly plastic and strain hardening material characteristics. The parameters that are investigated are chord depth–width ratio, eccentricity, chord preloading, and diagonal–chord angle. Interaction curves are presented that relate the diagonal and chord axial forces for different combinations of the parameters. It is shown that joints may suffer significant reductions in strength with an increase in eccentricity for the case when shear capacity of the chord's webs does not govern overall strength.Various detailing alternatives are investigated to improve joint capacity for prescribed weldment lengths. These include altering the diagonal–chord angle and the chord depth–width ratio.