01 May 1999
Bitumen Application Temperature Range for Surfacing: The optimum bitumen application temperature
range for surfacing is dependent upon the type and method of surfacing. For glaze coating, wherein a
relatively thin coating is desired, bitumen application temperature in the EVT range is generally
recommended. For aggregate surfacing, a lower bitumen application temperature is generally
recommended for the pour coat.
Bitumen Application Temperature Range for Adhering Insulation: The optimum bitumen application
temperature range for adhering insulation boards is dependent upon the type of insulation, type of
substrate, ambient temperature and wind conditions. Bitumen application temperature within or lower
than the EVT range is generally recommended.
Supplementary Recommendations Regarding Bitumen Heating: Excessive or prolonged bitumen
heating may have a deleterious effect on the physical properties of the product. Accordingly, the
following is recommended.
a. Bitumen in kettles or tankers should be kept approximately 14oC (25oF) or lower, below the
bitumen's flash point.
b. Bitumen should not be maintained above 260 C (500 F) for more than four hours unless
bitumen is being added and drawn off periodically.
c. If bitumen is held in a tanker or in storage for more than 48 hours, it should be kept
approximately 163 C (325 F) or lower.
Commentary on Bulletin 2-91 Revisions.
The major revision to this edition of the bulletin was the incorporation of separate EVTs for asphalt
mop application and mechanical spreader application. Bitumen application temperature range
information has also been added for surfacing and adhering insulation boards. Editorial changes have
also been made.
Although the bulletin is intended for built-up membrane systems, portions of it are also applicable to
certain aspects of hot-applied polymer-modified bitumen roof systems. Bitumen used to adhere base
and ply sheets, and bitumen used to adhere roof insulation, is generally recommended to be applied at
the temperature range recommended in this bulletin. However, the appropriate bitumen temperature
application range for adhering modified bitumen capsheets may be hotter than the ranged
recommended in this bulletin. For the recommended range when adhering modified bitumen
capsheets, consult the sheet manufacturer.
1. Cullen, W.C., "Equiviscous Temperature Concept Revisited", International Journal of Roofing
Technology, 1990, p. 46.
2. NRCA and Trumbull Research Report, "Temperature and Viscosity Effects on the Application of
Asphalt during the Construction of Built-Up Roofing Systems", September, 1988.
3. NRCA and Koppers Research Report, "Temperature and Viscosity Effects on the Application of
Coal Tar Products during the Construction of Built-Up Roofing Systems", December 1986.
Reprinted with permission of the National Roofing Contractors Association.