Weatherproof joint for exterior building panels

A fiber-reinforced plastic (FRP) panel comprising:

• an inner core material having a perimeter and forming at least one core channel that extends around the perimeter and inward a predetermined depth from the perimeter toward a center of the FRP panel;
• a first outer wall coupled to a first side of the inner core material;
• a second outer wall coupled to a second side of the inner core material opposite the first outer wall;
• and
• at least one elastic member received within the at least one core channel, the at least one elastic member forming a recess that extends along a top surface of the at least one elastic member and extends inward from the top surface toward a bottom surface of the at least one core channel,
• wherein the at least one elastic member forming a recess extending along a top surface of the elastic member and extends inwardly from the top surface of the at least one elastic member toward a bottom surface of the at least one core channel,
• wherein the recess of the at least one elastic member is configured to receive a joining member for joining to another FRP panel.