Self adherent water vapour permeable membrane comprising an adhesive composition

A self adherent, water vapour permeable membrane, for use in a building envelope, comprises a water vapour permeable membrane 1 and an adhesive composition 2 on at least one surface of the water vapour permeable membrane, wherein the adhesive composition comprises a hydrophobic adhesive polymer and hydrophilic microparticles. The hydrophobic adhesive polymer may be a pressure sensitive adhesive. Preferably, the hydrophilic particles may be polymeric and can be formed from water soluble ethylenically unsaturated monomer(s). A method for manufacturing a self adherent, water vapour permeable membrane is also claimed. The use of the self adherent water vapour permeable membrane in buildings for preventing the ingress of water and allowing the transmission of water vapour from the interior of the building to the exterior is also claimed. The membrane can be adhered to surfaces within a building envelope, which typically may be sheathing in wall applications, sarking board in roof applications or rafters.