Water that is not drained properly will find any weaknesses in the roof membrane and infiltrate the moisture barrier that the roof was designed to provide. The results can be anything from obvious water leaks inside the building to less apparent but just as costly damage such as saturated insulation or traveling leaks. Saturated insulation absorbs heat instead of repelling it as designed. Wet insulation, in addition to leaking, robs the educational or health care facility of the energy efficiency of a properly designed roof system. Traveling leaks are leaks that occur at one point on the roof but actually appear quite far away on the inside of the building.
Flat roofs have a lot of traveling leaks.
A solution to the problems of flat roof construction on existing buildings is retrofitting with the roof with steel structural standing seam panels. The method of reroofing over an existing roof is called retrofit roofing. Retrofit roofing should not be confused with roof replacement. Roof replacement occurs when the existing roof is removed and the same type of roofing is replaced or another type of roofing is used. Retrofit roofing is used almost exclusively to reroof flat built up or single ply roofs.