A high-performance butyl mastic tape used for jointing radon membranes, DPM, and DPC. This double-sided tape features a high-quality adhesive that bonds firmly to damp-proof materials or membranes, ensuring adhesion in moist environments like bathrooms, attics, or basements. The butyl material is totally damp-proof, preventing moisture seepage. It is supplied on a roll for ease of use. For application, overlap membrane material by a minimum of 150 mm and apply the tape between the layers. A length of Damplas single-sided jointing tape can be used to seal the overlap. This tape is also methane gas resistant (tested to ISO15015-1, achieves 0.07 ml/linear metre/day) and BBA-approved. It offers excellent adhesion to a wide range of building and construction membranes, including damp-proof and gas-protective membranes, with high tack and minimal waste or mess.