dampsperre

Dampsperre, or damp-proof membrane (DPM), is a thin sheet or coating designed to resist the diffusion of water vapor through building components. Its primary purpose is to reduce moisture transfer from warm, humid interiors into cooler structural elements where condensation or dampness could occur. By limiting vapor movement, damp spares insulation from becoming wet and helps prevent mold growth and material damage.

Common applications include floors under concrete slabs, basements and crawl spaces, and segments of walls in contact with earth or exterior moisture. In floors, a DPM is laid on the warm side of the insulation and beneath a concrete slab or between the subfloor and finished floor. In foundations, it is used to impede rising damp along masonry. In roofs and walls, vapor retarders may be specified to balance drying capacity with moisture control according to climate.

Materials range from polyethylene film (the most common form) to other polymeric sheets, aluminum foil laminates, and bitumen-based membranes. Dampsperre can be described as a vapor barrier (low-permeance) or a vapor retarder (higher-permeance) depending on the intended performance. Compliance is typically indicated by permeance ratings in local codes or by European standards such as EN 13984.

Installation requires continuous coverage with sealed joints and careful detailing at penetrations, edges and transitions to prevent punctures or gaps. The barrier should be installed on the correct side of insulation and protected from damage during construction; otherwise trapped moisture may occur. Damaged barriers should be repaired or replaced.

See also: damp-proof course, moisture barrier, vapor barrier.