Abstract: A waterproofing membrane including a layer of bentonite that has sufficient flexibility to be bent upon itself 360° around a 0.5 inch radius. The layer of bentonite is preferably made of bentonite particles compacted to at least 25 pounds per square inch and held together by an adhesive matrix. The waterproofing membrane is preferably four layers, including a scrim, a first compacted layer of bentonite particles secured to the scrim, and a water permeable layer disposed on the first layer of bentonite particles and second layer of bentonite particles compacted and disposed on the water permeable layer. The bentonite particles may be used on a surface of a thermal insulating board to form a composite waterproofing and insulating structure.