The APP Membrane Stands for Atactic Polypropylene Membrane is a special waterproofing material that is manufactured from bitumen they comes in rolls. These are commonly used to protect structures against hydrostatic pressure. Available in different thikness i.e. 1mm, 2mm, 3mm and 4mm. The membrane also available in centre core of HMHDPE Film/Fibre glass tissue/Non woven polyster.