Flashing a chimney on a roof with spray foam insulation (SPF) involves careful attention to waterproofing details to prevent leaks. The purpose of chimney flashing is to create a watertight seal where the chimney meets the roof surface, and with SPF roofs, this can be slightly more complex. Typically, step flashing is installed along the sides of the chimney, overlapping each shingle, while a counter flashing is embedded into the chimney masonry and overlaps the step flashing. This layered approach directs water safely away, reducing the risk of leaks. Over time, flashing can deteriorate due to weather exposure or improper installation, so checking for rust, cracks, or gaps is essential. Since SPF roofs are sealed and delicate to handle, avoid disturbing the foam unnecessarily. A safe DIY check includes visually inspecting the flashing edges for any visible gaps or signs of water damage inside your attic near the chimney.
While you can do a visual inspection yourself, flashing installation or repair on an SPF roof is usually best left to experienced roofers familiar with this roofing type, as improper work can damage the SPF layer or void warranties. When choosing a contractor, ask how they plan to protect the SPF foam while installing the flashing and whether they will use materials compatible with spray foam surfaces to avoid chemical reactions. Also, inquire if their method maintains the roof’s ventilation and moisture barrier integrity, as these impact long-term performance. Request proof of warranty coverage on both the flashing and the SPF roof work to ensure you are fully protected. Proper flashing installation protects your home and extends the life of your spray foam roof, making professional advice well worth considering.