Roofs are designed in an abundance of styles and combinations. Most roof designs have a pitch or slope. The slope of the roof allows it to shed water, reduce ultraviolet exposure and prolong the life of the roofing material. Roofing designs are selected to both protect the building and add ascetic appeal. Gable and Hip roofs are the most commonly seen roofs on homes. Flat roofs are often used to add curb appeal and save expense on construction. Each roof design is constructed differently and has potential problems if not installed and maintained correctly. When roof coverings have been changed as they wear out or renovations are undertaken, the roof design must be able to accommodate the new installation. Many roofs are designed using a combination of alternatives. The inspector will carefully check the roof framing where visible, the sheathing, flashing, and roof covering for any visible defects or wear. A badly designed or installed roofing system can be a source of constant problems and extensive damage to the inner building envelope.