In some cases, before proceeding with a roof installation, it can be beneficial to know exactly what layers of existing roofing, decking, insulation and/or other materials are on the roof. This can often be helpful in analyzing ventilation concerns as well as in looking at the condition of the roof decking. To do this, a “core sample” is removed by either sawing or hole-cutting into the roof. The core can then be removed and analyzed. The core must be replaced and securely sealed in order to prevent future problems.