Oil canning in EPDM roofing refers to those visible waves or ripples that appear on the membrane surface, often giving the roof an uneven, unsightly look. This happens primarily because EPDM is a flexible material that can expand and contract with temperature changes, and when it isn’t perfectly secured or installed flat, these movements cause the membrane to buckle or form ridges. Sometimes, oil canning occurs if the substrate beneath the EPDM isn’t smooth or if there’s improper tension during installation. While these ripples are generally more of an aesthetic issue and don't always indicate leaks, they can trap moisture and debris, potentially leading to further problems down the line.
To diagnose oil canning at home, visually inspect your roof for irregular waves especially after temperature swings or within the first year post-installation. Check for loose areas by gently pressing on the membrane—looseness or bubbles can signal tension issues. For safety, avoid walking heavily on the membrane; use binoculars or a drone for a closer look if you feel unsure. Fixing oil canning often means re-tensioning or re-adhering parts of the membrane, which is best left to a professional. When hiring a roofer, ask if they have experience specifically with EPDM roof repairs and how they ensure proper tensioning over time. Also, inquire about any warranty coverage for oil canning—this can save you money and trouble if the problem reoccurs later.