Features   Features Coal Tar built-up roofing provides one of the most durable roofing systems known due to its inherent waterproofing and weathering characteristics. Coal tar roofing systems are the time-proven roofing systems for level and low sloped roofs. Coal tar provides numerous advantages to an owner. Superior performance in the areas listed below make coal tar roofing systems unique in the roofing industry. Koppers Coal Tar Pitch, the traditional roofing grade coal tar, is manufactured to meet Standard ASTM D 450 Type I. Coal Tar has natural resistance to water, air, and water vapor penetration. A tight molecular structure enables coal tar to resist water penetration, oxidation of the roof surface as well as resistance to many of the common chemicals found in today's environment. Koppers roof warranties do not exclude coverage for areas of ponding water. Coal Tar roofing is self-healing. Alligatoring and hairline cracks common to most materials eventually allow damage to the roofing membrane. Coal tar has a property known as “cold flow” which acts to correct or lessen these conditions periodically. This “cold flow” feature permits the roof to slowly heal hairline cracks and alligatoring when roof temperatures reach the necessary level for “cold flow” to take place. This process will reoccur during the normal life expectancy of the roofing system. Although the ability of the coal tar to “cold flow” will decrease during its normal life, “cold flow” will continue in varying degrees provided the coal tar was installed in accordance with Koppers specifications utilizing Koppers products in Koppers roofing systems. Softening Point. Coal tar roofing pitch meets the applicable ASTM standard at the time of manufacture. At the time of application and after application, the softening point or other properties will change as a result of natural processes. If installed and maintained properly, any change in the properties of the coal tar products will not affect the ability of the roofing system to perform normally. See Effective Maintenance with Tar and Asphalt Roof Resaturants Effects of Temperatures on Coal Tar Products. Coal tar pitch is sensitive to temperatures above those permitted by the manufacturer’s specifications at the time of application and after application. To avoid damage to the roofing system or to avoid shortening of the normal life expectancy of a roofing system, do not: Exceed the application temperature ranges contained in Application Considerations, by degree or by duration during application; or Permit the roofing membrane to remain exposed without aggregate surfacing more than the limits specified in Surfacing Time.  Return to Built Up Roofing Systems