Estimating in Building Construction

Metals 143

FIGURE 12.11.Steel Decking

Productivity Rates. 

Steel Decking Labor Hours

(gauge) per Square

22 1.0 to 2.5

18 2.0 to 4.0

14 2.5 to 4.5

Decking is generally available either unpainted, primed,
painted, or galvanized. Accessories available include flexible
rubber closures to seal the flutes, clips that fasten the decking
to the purlins, lighting, and acoustical finishes.

Specifications. Determine the type of decking required,
thickness, gauge of metal, finish required on the decking as
received from the supplier, method of attachment, acces-
sories required, and the specified manufacturers.
Items that are necessary for the completion of the deck-
ing and which must be included in the specifications include
painting of the underside of the deck, acoustical treatment,
openings, and insulation.

Estimating. Because metal decking is priced by the
square (100 square feet), the first thing the estimator must
determine is how many squares are required. Again, a sys-
tematic plan should be used: Start on the floor on which the
decking is first used and work up through the building,
keeping the estimates for all floors separate.
Decking is usually installed by welding directly through
the bottom of the rib, usually a maximum of 12 inches on
center, with side joints mechanically fastened not more than
3 feet on center. The estimator will have to determine
approximately how many weld washers will be required and
how long it will take to install them. Otherwise, fastening is
sometimes effected by clips, screws, and bolts.
The estimator should consult local dealers and suppliers
for material prices to be used in preparing the estimate.
Materials priced f.o.b. the dealer will require that the estima-
tor add the cost of transporting the materials to the job site.
Once at the job site, they must be unloaded, perhaps stored,
and then placed on the appropriate floor for use. In most
cases, one or two workers can quickly and easily position the
decking and make preparations for the welder to make the
connections.
The estimator must be especially careful on multifloor
buildings to count the number of floors requiring the steel
deck and keep the roof deck and any possible poured con-
crete for the first floor separate. Most estimators make a small
sketch of the number of floors to help avoid errors. In check-
ing the number of floors, be aware that many times there may
also be a lobby level, lower lobby level, and basement.

EXAMPLE 12-3 DECKING

Determine decking for the sample project in Appendix A (Figure 12.2).

From the labor productivity rates in Figure 12.11 and assum-
ing a prevailing wage rate of $20.65 per hour, the following labor
cost calculations can be performed.

Labor cost ($)12 .6 hours$20 .65 per hour$260 .19

Labor hours6.3 sq 2 labor hours per sq12.6 labor hours

Using 22 gauge decking and 2 labor hours per square:

Add 5 percent for wasteUse 63 sq

Roof area (sq)6,000 sf> 100 sf per sq60 sq

Roof area (sf ) 60 ¿ 100 ¿6,000 sf

12–6 MISCELLANEOUS

STRUCTURAL METAL

Other types of structural framing are sometimes used. They

include structural aluminum or steel studs, joists, purlins,

and various shapes of structural pipe and tubes. The proce-

dure for estimating each of these items is the same as that

outlined previously for the rest of the structural steel.

1. Take off the various types and shapes.


2. Determine the pounds of each type required.


3. The cost per ton times the tonnage required equals the
   material cost.


4. Determine the labor hours and equipment required and
   their respective costs.

12–7 Metal Erection Subcontractors

Most of the time, these subcontractors can erect structural steel

at considerable savings compared with the cost to the average

general contractor. They have specialized, well-organized work-

ers to complement the required equipment that includes cranes,

air tools, rivet busters, welders, and impact wrenches. These fac-

tors, when combined with the experienced organization that

specializes in one phase of construction, are hard to beat.

Using subcontractors never lets the estimator off the

hook; an estimate of steel is still required because cost con-

trol is difficult to maintain and improve upon.

12–8 Miscellaneous Metals

Metal Fabrications. The metal stairs, ladders, handrails,

railings, gratings, floor plates, and any castings are all consid-

ered part of metal fabrications. These items are typically

manufactured to conventional (standard) details.

The estimator should carefully review the drawings and

specifications of each item. Next, possible suppliers should

be called in to discuss pricing and installation. It may be pos-

sible to install with the general contractor’s crews, or special

installation or equipment may be needed, requiring the job

to be subcontracted.

Ornamental Metal. Ornamental metals include orna-

mental stairs, prefabricated spiral stairs, ornamental

handrails and railings, and ornamental sheet metal. These

types of products are most commonly made out of steel, alu-

minum, brass, and bronze and are often special ordered.