Learning about roofing not only prevents fraud, but also enables you to get the best value for your money. Types of roof coverings include: asphalt shingles, metal, slate, tile, synthetic, or wood shake. Each of these are installed over a roof's structure and sheathing. Each varies in terms of life span, efficiency, cost, and appearance. To save money, instead of removing the old roofing, a new roof may sometimes be installed over an existing roof, then both may be removed later when an even newer roof is installed. Note that a roof can usually support only two layers. There are certain specialized terms that are helpful to know: Flashing, the material connecting roof coverings to vertical roof features like chimneys. Drainage system, the method of channeling water from the roof,including gutters and downspouts. Structural support, like beams and rafters. Sheathing, the layer of wood placed over the structural support. Fascia, the external covering at the top corners of walls. Rake, the inclined edge of a roof over a wall. Ridge, the top point of a roof where two sloping surfaces meet. Valley, the angle formed at the low point of two sloping surfaces. Eave, the underside of the overhanging part of the roof. Gable, the area under inclined edges of a roof. Ventilation louver, an opening in a gable to enable air circulation between the ceiling of a room and the roof support structure. Routine roof maintenance includes a self check in spring and fall. Look for loose shingles, algae, or an abnormal amount of roofing granules in the gutter. If you decide to get professional help, ask for a free estimate and a detailed contract with fully itemized costs, options, and debris removal. Ethical businesses will provide: warranty information, references, proof of insurance, and proof of license, if applicable. Getting three estimates with comparable materials can usually produce significant savings. For a complete checklist or a more thorough understanding of roofing or referrals, contact the National Roofing Contractors Association at www.nrca.net or 847-299-9070. Also you can ask the BBB for a free brochure entitled Home Improvement.