VERTICAL JOINT SYSTEM FOR SURFACE COVERING

A vertical joint system for a substrate having an opposed major first and second surfaces， the joint system comprising male and female joints (Jm， Jf) being non-symmetrical joints extending along opposite sides of the substrate， the male and female joints configured to enable two substrates with like joint systems to engage each other in response to a force applied in an engagement direction which is perpendicular to the major surfaces; the male and female joints each provided with two laterally spaced transversely extending surfaces (Cm1， Cm2; Cf1， Cf2) configured to enable the male joint of a first substrate (12a) to engage the female joint of a second substrate (12b) with the first and second transversely extending surfaces of the female joint (Cf1， Cf2) located relative to the first and second transversely extending surfaces of the male joint (Cm1， Cm2) to form respective first and second locking planes (18， 20) on an innermost and an outermost side of each joint， wherein the transversely extending surfaces are configured to enable relative rotation of two engaged substrates by up to 3° while maintaining engagement of the two substrates， and wherein at least one of the transversely extending surfaces associated with at least one of the locking planes has a profile of a continuous convex curve.