Experience with testing in accordance with EN 13948 has shown that flexible sheets for waterproofing with different thicknesses, different colours, different formulations, different surface finishing, and different internal fabrics, amongst others, have passed the test successfully. This document expresses the extrapolation rules of the results of root resistance testing in accordance with EN 13948 for roof waterproofing sheets manufactured in accordance with EN 13707:2004+A2:2009, and EN 13956:2012. Experience with testing in accordance to EN 13948 has shown that the main critical points are represented by the joints. If joints are done in a proper way, it will avoid the penetration of roots during the test.