Abstract: The invention relates to protective waterproof membranous sheeting which will prevent the passage of water and corrosive salt solutions into structures.The protection membrane comprises a bituminous adhesive waterproof sheet 1, a flexible polymeric protection grid 2 and a release sheet 3. The waterproof sheet 1 may comprise a fibre core in a matrix of a polymer modified bitumen polymer. The protection grid is partially embedded in the waterproof sheet 1, and is formed with drainage channels 13,14 on each face, provided by ribs or strands 4 and 5 defining the grid. The aperture size of the grid may be up to about 10 mm across. A filter web may be fixed to the face of the grid.