One or more test cuts can determine the materials and deck type. Most low slope roofs have the insulation immediately above the deck and the waterproofing layer on top of the insulation. Sometimes there are multiple layers of roofing systems. The deck type usually can be determined from underneath (you may have to pop a few ceiling panels). See our test cut page for examples of what different material looks like. Anyone can cut into a roof but most roofs need to be patched by a professional. For example – asphalt based patching products are chemically incompatible with most single ply membranes.