EPDM (ethylene propylene diene monomer) roofing is a popular single-ply membrane known for its durability and flexibility, making it a common choice for flat or low-slope roofs. Unlike some roofing materials, EPDM can perform well on very low slopes, even down to about 1/4 inch per foot (a 2% slope). This low slope requirement is because EPDM is fully adhered or mechanically fastened as a continuous membrane that resists ponding water. However, proper drainage is still critical to avoid water pooling, which can lead to premature membrane wear or leaks. If you suspect the slope is too low, a simple DIY check involves inspecting the roof after rain or heavy watering to see if any water remains standing more than 48 hours. A level or slope finder tool, often available at hardware stores, can also give you a quick estimate of your roof’s pitch.
While EPDM is tolerant of low slopes, extremely flat roofs below the 1/4 inch per foot guideline may need special design considerations. If water is ponding regularly, this is a red flag and an experienced roofing contractor should evaluate the situation. When calling a roofer, consider asking if the current roof design meets manufacturer specifications for slope and drainage, and whether adding tapered insulation or improving drainage solutions might be necessary. This helps ensure any repair or replacement adheres to warranty requirements and prolongs roof lifespan. Always emphasize to contractors that the roof must manage water effectively—questions about how their solution prevents pooling will guide you to quality advice.