The effect of heat-conditioning on the maximum tensile load and elongation properties at cold temperature of glass and organic felt, 4-ply reinforced asphalt built-up roofing (BUR) membranes was determined. Specimens were heat-conditioned at 65°C (150°F) for 1, 7, and 28 days. Both the conditioned and the unconditioned membranes were tested for maximum tensile load and elongation. The specimens were prepared in both the machine and cross-machine directions. The tests were conducted at room temperature and at seven temperatures ranging from 0 to -60°C (32 to -75°F). In general, glass-felt BUR membranes showed higher elongations than the organic-felt BUR. The maximum tensile loads for both membranes were in the same range for the machine direction. The glass-felt BUR was stronger in the machine direction. The maximum tensile load and elongation of glass felt BUR are affected neither by heating time nor by testing temperatures below -10°C (14°F). The maximum tensile load of organic-felt BUR increases and elongation decreases with cold testing temperatures.