Root Bloc 20 secondary root barrier is an optional addition to prevent again root penetration. Typically used in an intensive vegetative roofing assembly, Root Bloc 20 is a flexible and polymeric alloy geomembrane liner. ROOTBLOC™ 20 is a polyethylene composite geo-membrane specially designed as a barrier against root penetration in vegetative roof assemblies. Product is folded and rolled onto heavy-duty cores for ease in handling and installation. Laps of ROOTBLOC™ 20 are over-lapped 24 inches and sealed with 1/2 in bead of Henry HE925 BES Sealant.