Built-up roofing (BUR) is a traditional roofing system made of multiple layers of bitumen and reinforcing fabrics, often topped with gravel or mineral granules. The underlayment in a BUR system plays a crucial role as a protective barrier between the roof deck and the bitumen layers. It helps prevent moisture intrusion and provides extra durability. Typically, the underlayment should be a high-quality, non-perforated felt or synthetic material designed to resist moisture and chemicals in the bitumen. Underlayment requirements vary by region and roof design, but generally, a layer or two of fiberglass or organic felt is applied to ensure proper adhesion and protection during installation. If the underlayment is missing, torn, or improperly installed, you may notice bubbles, blisters, or early signs of roof wear, which can allow moisture to reach the deck and cause damage over time.
A simple DIY check is to visually inspect the roof if possible, looking for uneven layers, loose gravel, or any signs of wear that expose the underlayment or deck. While inspecting from inside, be alert for any water stains or damp spots on the ceiling, which might indicate underlayment failure. Because BUR systems are complex and involve hot asphalt and multiple layers, it’s best to call a professional roofer if you suspect underlayment issues or if maintenance is overdue. When speaking with a contractor, ask specifically what type of underlayment they recommend and whether it meets local building codes. Also, inquire about how they ensure the underlayment’s proper installation to avoid future leaks or delamination. This approach helps protect your roof investment and maintain your warranty coverage.