The APP membrane, short for Atactic Polypropylene Membrane, is a special waterproofing material that is manufactured from Bitumen. They comes in rolls. Each roll measures 10 metres by 1 metre and covers an area of 8.7 m²
Most are about 2 to 4mm thick. There are essentially 2 types of membranes, sheet based membranes and liquid applied membranes. Ideally, a waterproofing membrane should be strong, flexible, tear-resistant and elastic so that it can stretch to cover cracks and also move with the building.
A waterproofing membrane is a thin layer of material used to prevent water from contacting another material that it is placed over. Waterproofing membranes may be adhesive or simply laid on top of the material they are supposed to protect