A composite membrane comprising a layer of rubberized asphalt having a heavy duty plastic film layer continuously bonded to one side and, optionally, a layer of nonwoven geotextile continuously bonded to the other side. The membrane can be used in vertical or horizontal applications, and is particularly useful for its stress-relief properties that resist crack formation and propagation in concrete walls and slabs in addition to serving as a barrier to moisture, toxic substances and insects. An appropriate composite membrane of the invention can be advantageously utilized in positive side, blindside, underslab or split slab applications. The thickness of the composite membrane preferably ranges from about 30 mils to about 150 mils.