Built-up roofing systems and methods

A bitumen-based built-up roofing system comprising a structural deck covered with a membrane comprising:

• (A) at least two layers of reinforcement,
• (B) at least one layer of insulation wherein the bottom layer of reinforcement is attached to the upper most layer of insulation,
• (C) a base layer having an upper surface and a lower surface, wherein the lower most layer of insulation is attached to the upper surface of the base layer, and the lower surface of the base layer is attached to the structural deck,
• (D) a separately applied bitumen-based waterproofing adhesive between each of the layers of reinforcement, between the lower most layer of the reinforcement and the upper most insulation layer, between the insulation layers, and between the lower most insulation layer and the upper surface of the base layer whereby each of said layers is adhered to the bitumen-based adhesive applied between the layers,
• (E) a bitumen-based flood coat over the layers of reinforcement, and
• (F) a protective layer of mineral aggregate material embedded in the flood coat, wherein the bitumen in at least the flood coat comprises a coal tar composition prepared from a blend comprising:
• (1) from about 80 parts to about 98 parts by weight of coal tar having an overall float test of from about 50 seconds to about 220 seconds,
• (2) from about 2 parts to about 20 parts by weight of coal tar pitch having a softening point of from about 140 to about 160.degree. C., and
• (3) from about 1% to about 20% by weight, based on the total weight of the composition, of an acrylonitrile-butadiene copolymer.

A bitumen-based built-up roofing system comprising a structural deck covered with a membrane comprising

• (A) at least two plied layers of reinforcement, the bottom layer being attached to said structural deck,
• (B) a separately applied bitumen-based waterproofing adhesive between each layer wherein each ply is adhered to the bitumen-based adhesive applied between the plies,
• (C) a bitumen based flood coat over the plied layers, and
• (D) a protective layer of inert mineral aggregate material embedded in the flood coat, wherein the bitumen in at least the flood coat comprises a coal tar composition prepared from a blend comprising:
• (1) from about 80 parts to about 98 parts by weight of coal tar having an overall float test of from about 50 seconds to about 220 seconds,
• (2) from about 2 parts to about 20 parts by weight of coal tar pitch having a softening point of from about 140 to about 160.degree. C., and
• (3) from about 1% to about 20% by weight, based on the total weight of the composition, of an acrylonitrile-butadiene copolymer.