Estimating in Building Construction

102 CHAPTER TEN

Mesh reinforcing may be a welded wire mesh or
expanded metal. Welded wire mesh is an economical rein-
forcing for floor and driveways and is commonly used as
temperature reinforcing and beam and column wrapping. It
is usually furnished in flat sheets or by the roll. The rolls are
5 feet wide and 150 feet long. Wire mesh is designated on the
drawings by wire spacing and wire gauge in the following
manner: 6  610 ⁄ 10. This designation shows that the longitudi-
nal and transverse wires are spaced 6 inches on center, while
both wires are No. 10 gauge. Another example, 4  88 ⁄ 12 ,
means that the longitudinal wires are spaced 4 inches on cen-
ter, and the transverse wires are spaced 8 inches on center; the
longitudinal wire is No. 8 gauge while the transverse is No. 12
gauge. The takeoff must be broken up into the various sizes
required and the number of square feet required of each type.
It is commonly specified that wire mesh have a lap of one
square, and this allowance must be included: For example, a
6-inch lap requires 10 percent extra mesh, whereas a 4-inch
lap requires almost 6.7 percent extra. The mesh may be either
plain or galvanized; this information is included in the speci-
fications. Galvanized mesh may require special ordering and
delivery times of two to three weeks.
The 1/4-inch rib lath is designed primarily as reinforce-
ment for concrete floor and roof construction. The 1/4-inch
ribs are spaced 6 inches on center, and this reinforcement is
available only in coated copper alloy steel, 0.60 and 0.75
pounds per square foot. The width available is 24 inches with
lengths of 96, 120, and 144 inches, packed six sheets to a bun-
dle (96, 120, and 144 sf, respectively). Allow for any required
lapping and 3 percent for waste (for rectangular spaces).

The reinforcing steel must be elevated into the concrete

to some specified distance. This can be accomplished by using

concrete bricks, bar chairs, spacers, or bolsters, or it may be

suspended with wires. The supports may be plastic, galvanized

or zinc-coated steel, steel with plastic-coated legs, and other

materials. If the finished concrete will be exposed to view and

the supports are touching the portion to be exposed, consider-

ation should be given to using noncorrosive supports. Steel,

even zinc or galvanized steel, has a tendency to rust, and this

rust may show through on the exposed finish. A wide selec-

tion of accessories and supports are available.

When the reinforcing must be fabricated into a special

shape—perhaps round, spiral, or rectangular—it is usually

cheaper to have this done at a fabricating shop, which has the

equipment for bending these shapes. Thus, there would be a

charge in addition to the base cost of the reinforcing, but the

process provides speed and economy in most cases.

Corrugated steel subfloor systems are also used for

reinforcing concrete. When corrugated steel floor deck

material is used as reinforcing for the concrete, it also acts as

a form for the concrete that is to be poured on top of it. The

system may simply be corrugated deck with concrete or may

be as elaborate as supplying in-floor distribution of elec-

tricity, hot air, and telephone requirements. The more elab-

orate the system, the more coordination that is required

between the trades.

Steel deck subfloors are taken off by the square footage

required (also discussed in Chapter 11). Available in a variety

of heights and widths, the type used will depend on the span

and loading requirements of the job. Finishes include galva-

nized, galvanized with primer on the underside, and phos-

phate treated on upper surfaces with primer on the underside.

Wire mesh is sometimes specified for use as tempera-

ture steel, in conjunction with the steel decking. The estima-

tor must include it in the takeoff when it is required.

Estimating Reinforcing Bars. The linear footage of

rebars can most often be worked up from the concrete calcu-

lations. The sections and details must be checked to deter-

mine the reinforcing requirements of the various footings.

The various footing sizes can generally be taken from the

concrete calculations and adapted to the reinforcing takeoff.

EXAMPLE 10-9 FOUNDATION REINFORCING

For this example, determine the quantity of reinforcing steel

required for the side A continuous footing of the building found in

Appendix A. From Figure 10.3, which was used to quantify the con-

crete, the dimensions for all of the sides can be found. From that

table, side A is 39 10 . This footing has reinforcing bars that run

both the long and short dimensions. Figure 10.21 is an excerpt of

the details found on sheet S8.1 of the project found in Appendix A.

Continuous Footing Short Bars

Add 1 to get the number of barsUse 45 bars

Number of short bars39.833¿>0.916744 spaces

Number of short bar spaces 39 ¿ 10 – > 11 – spacing

FIGURE 10.19.Weights and Areas of Reinforcing Bars.

FIGURE 10.20. Splice Requirements (Minimum splice is 1 0 ).