The final profit or loss on a structure is often decided in the estimating or bidding stage before a job actually starts. Basically the cost of forming depends upon thickness, height, and length of wall but there are also many other factors involved that are not always easy to evaluate and some of which are even likely to be unforeseen.
To begin the estimate the contractor must consider what forming equipment is available, how much of the needed equipment is available, how much of the needed equipment he owns and how much he must rent or purchase. The next step is to analyze the job in terms of what types of equipment are needed- prefabricated, job-built or specials.
Once the estimate is started it proceeds according to the following four steps, usually in this sequence but not always: first, analysis of the total job. Many estimators prepare a rough estimate at this point to determine the amount of concrete to be formed, expressing it in terms of square feet of contract area. This will provide a rough indication of what percent of the total job is concerned with forming. It will also aid in selection of forming equipment. Second, examination of equipment of systems available. If the contractor owns forming equipment he may prepare a detailed take-off of the job to see if his inventory is adequate or if additional equipment andmaterials are necessary. If new equipment is to be rented or purchased, the take-off will be of great assistance in planning and scheduling. The take-off will be especially helpful if he plans to build the forms himself. Third, consideration of the effect of the choice of formwork on the total job. With estimates on prefab forms or job-building, or both, the contractor can compare figures and reach a conclusion on the best and most economical way to proceed. And fourth, consideration of factors other than formwork that can affect results. These would include job conditions, weather, condition of equipment, and strikes among the trades.