A retention clip for use with a panel system has a base plate having a pair of opposing flanges at least one of which is configured for attaching to a support structure. An upright extends between the base plate and a top plate having a pair of opposing flanges and defines opposing first and second surfaces that in use are dimensioned to engage opposing first and second ends of a pair of first and second adjacent panels. At least the first surface supports a spacer element that is configured to prevent mutual abutment of opposing ends of the first and second panels at least during construction of the panel system.