Estimating in Building Construction

100 CHAPTER TEN

FIGURE 10.17.Labor Productivity Rates—Placing Concrete.

Productivity Rate

Type of Placement (Labor Hours/c.y)

Continuous Footing—Direct Chute 0.4

Spread Footing—Direct Chute 0.873

Drilled Piers 0.320

Formed Piers 0.873

Foundation Walls—Direct Chute 0.5

Grade Beams 0.4

Slab—Direct Chute 0.32

10–3 Reinforcing

The reinforcing used in concrete may be reinforcing bars,

welded wire mesh (WWF), or a combination of the two.

Reinforcing bars are listed (noted) by the bar number, which

corresponds to the bar diameter in eighths of an inch. For

example, a No. 7 bar (deformed) has a -inch nominal

diameter. The No. 2 bar is a plain round bar, but all the rest

are deformed round bars. The bar numbers, diameters,

areas, and weights are given in Figure 10.19.

Reinforcing bars are taken off by linear feet. The takeoff

(workup) sheet should be set up to include the number of

the bars, pieces, lengths, and bends. Because reinforcing bars

are usually priced by the hundredweight (100 pounds, cwt),

the weight of reinforcing required must be calculated. The

steel can be bought from the mill or main warehouses, and

the required bars will be cut, bundled, and tied. Bars will also

be bent to job requirements at these central points. Bars pur-

chased at smaller local warehouses are generally bought in

20-foot lengths and cut and bent in the field. This process is

usually more expensive and involves more waste. When time

permits, the reinforcing bars should be ordered from the

mill or main warehouse and be shop fabricated. Often the

fabricators will provide the required shop drawings. Check

the specifications to determine the type of steel required and

whether it is plain, coated with zinc, painted with epoxy

paint (typically green), or galvanized. Zinc coating and

galvanizing can increase the material cost by as much as

150 percent and often delays delivery by many weeks. Rebar

painted with epoxy paint increases the cost by about 20 per-

cent and has the advantage that damage to the paint can be

touched up in the field.

Allowance for splicing (lapping) the bars (Figure 10.20)

must also be included (lap splicing costs may range from 5 to

15 percent, depending on the size of the bar and yield

strength of steel used). Waste may range from less than

1 percent for precut and preformed bars to 10 percent when

the bars are cut and bent on the job site.

7 > 8

FIGURE 10.16.Slab Takeoff. 

Labor Costs. The labor costs are found by multiplying
the quantity takeoff by the appropriate productivity rate.
Figure 10.17 shows various productivity rates for placing
concrete in various situations.

EXAMPLE 10-8 LABOR COSTS

Find the labor cost for placing concrete in the 3 2 -wide conti-
nuous footings. From the concrete takeoff in Figure 10.7, there
are 42 cy of concrete. Using that quantity and the labor productiv-
ity information from Figure 10.17, the following calculations can
be performed.



Figure 10.18 is the priced-out estimate for all the concrete in
the foundation of the small commercial building.

Labor costs ($)$229 .50

Labor costs ($)17 hours$13 .50>hour

Labor costs ($)HoursWage rate

Labor hours17 hours

Labor hours42 cy0 .4 labor hours>cy

Productivity rate (labor hours>cy)

Labor hoursQuantity (cy)