A joint for fluid storage tank insulation systems designed to be a centralexpansion joint which forms a fluid-sealed recessed channel having aridge-like cap. Water and moisture are directed away from the centralexpansion joint by the ridge-like cap. Any water that breaches the capenters the recessed channel and flows out of the expansion joint withoutdamaging tank insulation material. With installations having multipleexpansion joints, at least one of the expansion joints can be equipped withan inverted cap to form a gutter within such expansion joint.
