- Q. What is the life expectancy of hot-mopped asphalt on a flat roof? Will aluminum paint extend the life of the roof? If so, how often should the roof be recoated with the paint?
A.The average life expectancy of a hot-mopped asphalt roof is 15 years. If the roof drains well, its life span might be longer. The edge details are critical to the life of this type of roof. Joints in any edge metal must be maintained regularly, since the metal expands and contracts at a different rate than the roofing, which tends to crack the roofing at the joints. An aluminum coating can extend the life of the roof because it reflects more heat, reducing alligatoring. The aluminum paint should be reapplied every three to five years.