This method would result in more accuracy than the average method. The difference between the two totals would indicate the total soil either required to be brought in or removed. One would then multiply the area of each of these blocks by the difference determined from each of these blocks and the sum of these numbers to determine the total amount of cutting or filling. Block or Grid Method: In the block (or grid) method, one would divide an area up into smaller areas and determine the amount of difference between the existing and finish grade in each of those areas.It would be most appropriate to use this method as either a preliminary estimation method or on a smaller scale project. This would roughly determine the overall amount of fill or excavated soil that would be necessary to transport to or from the site. Average Method: In the average method, one would first determine the average level of existing conditions, then the average level of the final proposed conditions, and finally multiply this difference by the area of the work.Units of measure for typical items include: units for items such as doors, windows, drains, catch basins, manholes, and plumbing fixtures feet or meters of length for items such as pipes, guide rails, and striping square feet or square meters of area for items such as clearing and grubbing, paint, and flooring cubic yards or cubic meters of volume for items such as concrete, aggregates, earthwork excavation, soil, and backfill and tons of weight for items such as structural steel and reinforcement. Likewise, a calculated number of doors on a project would be multiplied by unit cost defined as a cost per unit to determine the overall cost for the doors on a project. For example, a calculated volume of soil in cubic yards would be multiplied by a unit cost defined as cost per cubic yard. The cost component of an estimation is determined by multiplying the material quantity by the corresponding unit cost to determine the overall cost for the material. This could be based on volume, area, length, unit count, or overall weight, depending on the material. The calculations for an estimation depend upon the typical unit of measure which is used for the material being estimated. The material component of the estimation is often referred to as a "take-off," as it involves the calculation of material quantities based on plans, sections, elevations, or other design drawings. As the design progresses, the amount of design contingency may be lowered since there is typically less uncertainty about the design as a project progresses. ![]() This is often provided as a percentage increase in the overall project cost. Given the uncertainties of a design during the early stages of development, design contingencies are typically added to early estimates to reduce the risk of going over the construction budget in the project design at a later stage. This may not be a very accurate estimate, but it may be good enough to allow the design team to work with a general sense of an item's cost while detail on the design elements has yet to be determined. One might, for example, have a general idea of the typical cost of a parking lot at grade on a square footage basis and apply that number to the particular area which is proposed on a given project. ![]() Schematic level design, for example, lends itself to rough estimates, which can be based on an engineer's previous experience with costs.
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