Roof Leak Repair in Knoxville TN. This roof leak first looked like it was coming from the metal exhaust pipe from the furnace. This is a common place for roofs to leak. An attic inspection was performed, and it was evident that the area around the furnace exhaust had been leaking but could have been something else. Once it was inspected on the roof, It appears that that exhaust could leak, But there was a nail pop in the area of this roof leak, which is the most likely cause of this issue.