Built-Up Roofing (BUR) is a traditional roofing system made by layering multiple sheets of asphalt and reinforcing fabrics to create a tough, durable surface. Over time, blisters or bubbles can form on these roofs due to trapped moisture or air within the layers. This happens when water gets under the roofing material or when trapped vapors expand under heat. If left unchecked, blistering can cause parts of the roof to weaken or flake, increasing the risk of leaks. Simple diagnostics include looking for raised, rounded areas on the roof surface that feel soft or spongy to the touch. A safe DIY check involves gently pressing around a blister to see if it’s firm or if water seeps out, but avoid puncturing the blister as this can lead to further damage and void warranty coverage.
If you notice significant blistering or multiple areas spreading across your roof, it is best to call a professional roofer experienced with BUR systems. A contractor can assess whether the blisters are superficial or signs of deeper damage that might require patching, spot replacement, or more extensive repairs. When speaking with your roofing expert, ask about the recommended fix for blistering on BUR roofs and how it affects your roof’s warranty. Another useful question is whether the roof has adequate ventilation, as poor ventilation often contributes to blistering by allowing moisture buildup. Having a clear understanding of both the cause and the solution helps you avoid rushed repairs that might only be temporary.