Leaks in an aging built up roof surfaced with aggregate such as slag or gravel can be tough to locate unless there are visible clues such as blistering, ridging, splitting, cracks in sealant around pipe penetrations or equipment or at pitch pockets.
When leaks seem to occur in a wide expanse of open roof area with no clues, try this:
Spread out a sheet of clear plastic sheeting and secure the perimeter with weights to prevent wind uplift, then observe that area under the heat of the sun. The damp areas should form more condensation on the underside of the clear polyethylene helping to isolate the leak area for repair.
Larger areas of dampness are generally located with infrared photography or mapping the areas with an inductance type moisture meter.
The aggregate surface can be swept back to search for isolated defects, but if the water is simply seeping through the roof, this can be an indication that the asphalt has deteriorated within the plies. Sealing the surface in that area may provide a temporary cure, but these symptoms may indicate a more thorough solution is needed.
For additional information about Commercial Roofing please see: CommercialRoofingManagement.com