Estimating in Building Construction

96 CHAPTER TEN

The remaining element of the drilled piers is to determine the volume
of the shaft, which is done by subtracting the height of the bell from
the pier depth. However, the shaft typically extends 6 inches through
the bell requiring an extra 6 inches to be added to the shaft length.

This length of the shaft is then multiplied by its cross-sectional area
to determine its volume.

Formula 10-5

Shaft volume26.15 cf

Shaft volumea

1.5¿^2

4

b(14.8¿)

Shaft Volume

Shaft volumea

S^2

4

b(Length of shaft)

Length of the shaft14.8¿

Length of the shaft16.0¿1.732¿0.5¿

The volume of the shaft and pier can then be added together and

multiplied times the number of piers to determine the total volume.

The bell volume can be verified using the 60-degree table in

Figure 10.6. From this table, the bell height is 1.73 feet and the

volume is 8.96 cf per bell, which match the previous calculations.

Figure 10.7 is the workup sheet for the spread and continuous foot-

ings for the building in Appendix A. 

Use 5 cy

Volume of concrete (cy)3.89 cy1.104.3 cy

Add 10 percent for waste

Volume of concrete (cy)105 cf>27 cf per cy3.89 cy

Volume of concrete in piers (cf ) 3 (8.96 cf26.15 cf)

Volume in shaft)

Volume of concrete in piersCount(Volume in bell

FIGURE 10.7.Concrete Footing Takeoff.

EXAMPLE 10-4 FORMED PIERS

Use 1 cy 

Volume in formed piers0.786 sf 3 ¿ 7 – 2.8 cf

Cross-sectional arear^2 0.5¿0.5¿0.786 sf

Height

Volume in formed piersCountCross-sectional area

EXAMPLE 10-5 FOUNDATION WALLS

The concrete for the foundation walls is done in substantially the
same manner as the spread footings. In the small commercial build-
ing example, the building perimeter foundation walls are 1 2 thick
and the interior walls are 1 0 thick. Figures 10.8 and the table in

Figure 10.9 detail the linear feet of 1 2 -thick foundation walls. In

addition, side B is 8 4 tall as compared with 3 8 high for the

remaining 1 2 -thick walls. This is why, side B is not included in

Figure 10.9.

Spread footings typically have projecting formed piers that support
the building structure. The small commercial building has one
formed pier. This pier, as shown in Figure 10.4, is 1 foot in diameter
and 3 feet, 7 inches tall (sheet S8.1 details 1, 7, and 16 in Appendix A).
The volume of the formed pier is found by multiplying the cross-
sectional area by its height.