This European Standard specifies the methodology for laboratory evaluation of the performance of water repellent products on porous inorganic materials. It is based on the measurement of several parameters which assess the performance of the product using standard test methods before and after ageing. Acceptable performance within the laboratory does not constitute a blanket endorsement of application in every situation. The particular context of the heritage object, including such factors as material designation, condition, exposure, salt content and problems related to water ingress requires further investigation.