A sheet-like structure comprising two layers of respective bituminous compositions, each including a polymer, one layer being substantially non- adhesive and the other layer being a pressure-sensitive adhesive and, between the layers and in intimate contact with each layer, a coating of an oil resistant material. A method of preparing the structure includes forming one of the layers, spraying onto that layer, when it is hot, an oil resistant material in liquid form, allowing the liquid to solidify to form a coating on that layer, and applying the other layer, when it is hot, to the exposed face of the coating.
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