Aldercourse GRA is an aluminium cored damp-proof course, developed in combination with Alderprufe MR50 or GRA to provide a continuous “through the wall to floor” junction. Both products have a low permenance of methane and other gases including radon. Aldercourse GRA is suitable for use as the associated damp-proof course particularly where resistance is required to the ingress of methane. It may be used in conjunction with Alderprufe MR50 or GRA and similar methane retardant membranes. If resistance to methane is a factor, great care must be taken with detailing on all parts of the structure.