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The degree of accuracy used in the estimation of various material quantities used in the construction is crucial. This is to prevent cost estimate errors due to lack of proper accuracy and time consuming because of considering great accuracy which is not practical.
Degree of Accuracy in Estimating Construction Works
The accuracy considered in preparing an estimate is based on the unit of payment and the rate of the item. The higher the rates the greater should be the accuracy with which the quantities are computed. The dimensions need to be absolutely correct If the rates are high and payments are per unit.
Nonetheless, taking dimensions to nearest 1 to 0.5 cm may be permitted for practical reasons. However, extreme accuracy is not needed if rates are low and paid for % to ‰ unit.
Reduction or subtraction of a few centimeter to length or height of a wall where masonry is paid per cubic meter would not make great difference. In contrary, the width and thickness of the wall must be measured with great accuracy. This is because half centimeter or quarter centimeter would affect the result significantly. Table 1 provides general approximation for various measurements and construction items.
Table 1 Degree of Accuracy for Various Measurements and Construction Works
|Items||Degree of Accuracy|
|Dimensions||Measured to the nearest 1 cm or 0.01 m|
|Areas||Computed to the nearest 0.01 square meter|
|Cubic||Calculated to the nearest 0.01 cubic meter|
|Thickness of slab||Measured to the nearest 0.5 centimeter or 0.005 meter|
|Partitions||Measured to the nearest 0.5 centimeter or 0.005 meter|
|Sectional dimensions of columns, pillars, and beams||Measured to the nearest 0.5 centimeter or 0.005 meter|