ISO 18319:2015 specifies requirements for fibre-reinforced polymer (FRP) sheets for upgrading of concrete members. The methodologies to express the mechanical properties as characteristic values, appearance and dimensions, and sampling test are specified in this International Standard. The properties for design are calculated from the characteristic values, as prescribed in an appropriate design code which is in accordance with ISO 14484. The fibre orientation of the FRP sheets covered by this International Standard is unidirectional.