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Accurate estimates of cost are vital to the suc- cess of a construction project. Developing such estimates in great detail is the responsibility of the construction estimator. Usually employed by a gen- eral contractor, the construction estimator factors in everything from the price of lumber to the cost of renting a large crane for a day, the labor pay rates to insurance coverage, and expected loss of time resulting from bad weather. The resulting estimate is used as the basis for the contractor to competitively bid on the construction contract. For firms building single homes or residential developments, such an estimate is used to set the selling price of the homes. Construction estimators usually begin with a set of detailed building plans that provide dimensions and other information needed to begin the estimate. In most cases, the estimator also visits the site. This visit provides information on terrain, site access, drainage, and the availability of utilities. Next, careful analyses of material and labor requirements are done. These are called takeoffs and are entered on standard estimating forms. The estimator must identify and enter on the forms the exact quantities of each item that the contrac- tor must provide. If portions of the work (such as plumbing or electrical) are subcontracted, the esti- mator must usually analyze the bids submitted by the subcontractors. Decisions involving sequenc- ing of operations must be made, since improperly scheduled equipment, materials, or work crews may cause delays and increased costs. Allowances must be made for shipping delays, waste and damage to materials, weather problems, and so on. While most construction estimators are employed by building contractors, some work for large architec- tural or engineering firms. Estimators may also operate their own consulting businesses, providing fee-based services to contractors, government agencies, and building owners or financing organizations. Educational requirements for construction esti- mators usually consist of a degree in a field such as construction management, engineering, or archi- tecture. A strong aptitude for mathematics and pro- ficiency with computer software are also valuable assets. Many estimators also have practical expe- rience in construction work, giving them familiarity with materials, job practices, and the various spe- cialty trades. Additional on-the-job training is usually provided, since each company has its own specific way of preparing and presenting estimates. Professional certification is voluntary, but ben- eficial. Such certification is administered by two professional organizations—the Association for the Advancement of Cost Engineering and the Society of Cost Estimating and Analysis. The requirements vary, but include a number of years of professional experience and passing an examination.