A roof is part of the building envelope typically covering the uppermost part of the building. A well designed and constructed roof will stop moisture from entering the building and will typically keep the building insulated. Roofs generally consists of three (3) components: the waterproofing layers, the insulation and the supporting structure carrying the waterproofing layers.
The waterproofing layers are designed to prevent moisture from entering the structure. The layers are typically in the forms of shingles or tiles, rolled or liquid applied membranes or panelized systems.
The insulation layer can be installed above (inverted), below (conventional) or between the membrane and roof structure. The insulation is designed to create a barrier to reduce the amount of thermal loss or gain of a building (loss of heating or cooling or reduce the amount the building is heated or cooled by the surrounding environment).
The roof structure can be low-slope (flat) or sloped with beam, rafter and decking components constructed of either wood, concrete or metal. The roof structure is designed to support the membrane, insulation and any additional dead or live loads such as mechanical rooftop equipment, pedestrian traffic or snow and ice.
Due to the importance of the roof as the first line of defense to protect the occupants and contents of the building, it is often considered a high priority component. Quite often there are common deficiencies in roofing design, construction, materials and maintenance. Owners often spend large amounts of money on roofing systems in the form of on-going maintenance and replacement. Roofs should be routinely inspected, especially during the due diligence stage of a property acquisition to avoid unforeseen costs. Additionally the management of water plays a crucial role in the success of a roofing system.