Correct identification of single-ply materials is important to ensure repairs are compatible with the existing roof system. Because white reflective single-ply surfaces are common with many single-ply materials, correct identification can be challenging. The following are field tests that may be used to help identify the type of single-ply membrane material in an existing roof system.

• The shedding of top surface material, also termed “chalking,” is characteristic of aged CSPE roof membranes. Staining of hands and shoe soles with white powdery material typically is evidence of chalking and may be used to identify CSPE roof membranes.
• Surface contaminants tend to be difficult to dislodge from aged PVC membranes as compared to aged TPO membranes. Simply dragging a shoe sole across the surface of an aged single-ply membrane may provide clues to help identify the material. With TPO membranes, it is typical to see stark contrast between the bright patch of the cleaned-off spot and the surrounding area. The results vary with PVC membranes and depend on the specific product but typically, surface contaminants tend to smear or streak when subjected to this test.
• PVC and TPO materials behave differently when ignited. Burning PVC resin emits bright green flame and ceases burning when the ignition source is removed. Burning TPO resin emits yellow flame and typically continues burning when the ignition source is removed.
• Depending on the age of the material, when a sample is cut from an existing PVC roof membrane, characteristic PVC plasticizer smell may be detected coming from the membrane underside.
• Black bleed-out along hot-air welded seams indicate the membrane is probably PVC material.