Describes origin of tobacco juicing and the effects this residue may have on modified bitumen roofs. Provides ways to minimize/eliminate residue runoff.
The formation of a “tobacco-juice” residue, so named for its color, is the normal result of the weathering of all asphalt-based products (i.e., roof coatings, base and cap sheets and shingles — to name a few), regardless of their manufacturer. A certain chain of exposure conditions — intense sunlight, sizable accumulations of moisture/dew, and a prolonged lack of rain — cause the formation of this residue. Once the residue has been washed away in the first rainy season, it is not likely to reoccur.
The residue will not affect the performance of the roof and should not be considered a performance problem. If any accumulation of this liquid residue occurs prior to coating, the proper bonding of coatings to the roof surface may be adversely affected. Finished roof surfaces which are continuously subjected to “tobacco-juicing” should be hosed off regularly, as “tobacco-juicing” residue may cause the peeling of acrylic and aluminum coatings. Preparation of the roof for coating should conform to the recommendations of the Roof Coatings Manufacturers Association (RCMA) and the Asphalt Roofing Manufacturers Association (ARMA) to help ensure proper adhesion.
Though it may not be possible to control environmental elements that cause the formation of the residue, the following recommendations can be utilized by the specifier, contractor or owner to minimize the aesthetic conditions associated with “tobacco-juicing”.
- Require coping metal on parapet walls where the tops slope outward, are rounded, or have no lip on the outside edge.
- Hose down the roof at regular intervals during long, dry periods of the first summer after installation.
- Using a solvent-type fibered aluminum coating, or acrylic coating, coat the field membrane. Coat all asphalt emulsions after they are thoroughly dried. Coat plastic cements and other solvent vehicle asphalts after they have cured for at least thirty days.
The problems associated with asphalt residue can be minimized if the necessary steps are taken by the specifier, contractor and owner.
*DISCLAIMER OF LIABILITY: This document was prepared by the Asphalt Roofing Manufacturers Association and is disseminated for informational purposes only. Nothing contained herein is intended to revoke or change the requirements or specifications of the individual roofing material manufacturers or local, state and federal building officials that have jurisdiction in your area. Any question, or inquiry, as to the requirements or specifications of a manufacturer, should be directed to the roofing manufacturer concerned. THE USER IS RESPONSIBLE FOR ASSURING COMPLIANCE WITH ALL APPLICABLE LAWS AND REGULATIONS.
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