Patent CA-2279304-A1 (CA)
Title: Built-up roofing systems and methods
Inventor: BRZOZOWSKI KENNETH J
IPC: C08L95/00
Filed: 1999-07-29
Abstract: In one embodiment, this invention relates to 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 firmly 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°C, and (3) from about 1 % to about 20% by weight, based on the total weight of the composition, of an acrylonitrile-butadiene copolymer.      In another embodiment, the present invention relates to a coal tar impregnated reinforcement sheet useful in particular in bitumen-based built-up roofing systems which comprises a layer of reinforcement such as a felt which has been impregnated with a coal tar composition as described above.     In yet another embodiment, the invention relates to a method of recoating a bitumen-based built-up roofing membrane which comprises the steps of: (A) removing loose mineral aggregate, if any, from the surface of an existing roofing membrane, (B) cleaning the surface of the existing roofing membrane, (C) applying a flood coat over the cleaned surface, and (D) embedding a layer of inert mineral aggregate material into the flood coat wherein the flood coat comprises the coal tar composition as described above.      The invention also relates to a method of re-coating a built-up roofing system having a mineral-surfaced cap sheet which comprises the steps of: (A) cleaning the surface of the mineral-surfaced cap sheet of an existing roofing membrane, (B) applying a flood coat over the cleaned surface, (C) embedding a layer of inert mineral aggregate material into the flood coat wherein the flood coat comprises the coal tar composition described above.      A method of re-covering a bitumen-based built-up roofing membrane is also described which comprises the steps of: (A) removing loose mineral aggregate or mineral surfacing, if any, from the upper surface of an existing roofing membrane, (B) cleaning the upper surface of the existing roofing membrane, (C) applying one or more layers of reinforcement, the bottom layer being attached to the cleaned upper surface of the existing roofing membrane, (D) separately applying a bitumen-based waterproofing adhesive between each layer of reinforcement when more than one layer is applied, and between the bottom layer of reinforcement and the cleaned upper surface of the existing roofing membrane, wherein each reinforcement layer is firmly adhered to the bitumen-based adhesive applied between the layers, and the bottom layer of reinforcement is firmly adhered to the cleaned surface of the existing membrane, (E) applying a bitumen-based flood coat over the applied reinforcement layer or layers, and (F) embedding a protective layer of inert mineral aggregate material into the flood coat, wherein the bitumen in at least the flood coat comprises a coal tar composition as described above.