Modified bitumen roofing is a popular choice for flat or low-slope roofs, often selected for its durability and waterproofing qualities. When considering whether to overlay an existing modified bitumen roof or perform a complete tear-off, it’s important to understand what each involves. Overlay means installing new layers directly over the old roof, which can be faster and less expensive initially, but may hide problems like deteriorated decking or trapped moisture. Tear-off removes the old roof down to the deck, allowing for a thorough inspection and repair of any underlying issues, but it’s more labor-intensive and costly. Simple diagnostics you can do yourself include looking for signs of bubbling, peeling, or cracks on the current surface, as well as checking the attic for any signs of leaks. If the existing roof’s structure feels spongy or you notice persistent water stains inside, these are red flags that a tear-off might be necessary.
For any DIY checks, walk the roof carefully to avoid damage, and ensure the weather is dry and safe. Look closely at flashings and seams for cracks or gaps, which are common failure points. However, modified bitumen roofing involves layers of cement or adhesive materials and specialized heat-welding, so if you’re unsure about the extent of damage or integrity of the existing roof, it’s wise to call a roofer. When consulting a contractor, ask if they recommend a full tear-off or an overlay based on your roof’s condition and local climate, and how the warranty will be affected by their choice. Also, inquire about the type of underlayment and ventilation improvements they suggest, since these can impact the roof’s lifespan regardless of the installation method.