Pre-fabricated waterproofing membrane made of distilled bitumen and elastomeric polymers (SBS) reinforced with a woven non woven single strand composite polyester fabric, with high mechanical characteristics and excellent dimensional stability. The particular structure of these products make them suitable for the waterproofing of complex works where the stress on the waterproofing system require the use of products with proven reliability. Due to the characteristics, the membranes of the GRID BIT SBS VIADUCTS series are used with success for the waterproofing of both civil and industrial works, in particular for those with great mechanical stress such as: bridges, viaducts, water works, foundations, parking lots.