400 Micron DPM 4m x 20m Damp Proof Membrane | Radon Barrier & Heavy-Duty Floor Sheet is a durable 400-micron polyethylene damp proof membrane designed to provide an effective moisture barrier beneath floors, concrete slabs, and building foundations. With a generous 4m x 20m size covering approximately 80m2, it helps reduce moisture penetration from the ground and can be used as a radon barrier where the appropriate installation system is specified. Ideal for construction, flooring, foundations, basements, and concrete projects, this heavy-duty DPM floor sheet offers reliable moisture protection and easy site installation.