Steel joint capacity depends on the joint details and the associated geometric values. This paper focuses on the static behavior of multi-planar out-of-plane overlapped KK-joints, under symmetrical compressive and tensile loading, with different joint details namely; (a) joint with hidden weld, (b) joint with no hidden weld, (c) joint with a non-through stiffener, and (d) joint with a through stiffener. The study considered four experiments involving each of the four types of joint details, and considered finite element numerical simulations parametric studies covering extensive and practical geometric variables. The results reveal that (a) welding or not welding the hidden seam of a through brace associated with KK-joints has marginal effect on the capacity of such joints. (b) A non-through longitudinal stiffener detailing for a KK-joint results in 5% to 68% increase in the joint capacity, and obviously the actual percentage increase depends on the values of various geometric parameters. (c) A through longitudinal stiffener detailing for KK-joint results in about 20% to 200% increase in the joint capacity. In order to provide design guidance for practicing engineers, empirical equations have been derived for multi-planar out-of-plane overlapped KK-joints containing non-through or through stiffener.