Estimating in Building Construction

136

METALS

CHAPTERTWELVE

12–1 General

This chapter covers structural metal framing, metal joists,
metal decking, cold-formed framing and metal fabrications,
ornamental metal, and expansion control assemblies. The
structural products are most commonly made of steel and
aluminum. The rest of the products are available in a wide
range of metals, including steel, aluminum, brass, and
bronze.

12–2 Structural Metal

General contractors typically handle structural metal in one
of two ways: either they purchase it fabricated and erect it
with their own construction crew, or they have the company
fabricate and erect or arrange erection by another company.
Many contractors do not have the equipment and skilled
personnel required to erect the structural metals. The struc-
tural metal includes all columns, beams, lintels, trusses,
joists, bearing plates, girts, purlins, decking, bracing, tension
rods, and any other items required.
When estimating structural metals, the estimator
should quantify each item such as column bases, columns,
trusses or lintels, separately. Structural metals are purchased
by the ton. The cost per ton varies depending on the type
and shape of metal required. Labor operations are different
for each type.
The estimate of the field cost of erecting structural met-
als will vary depending on weather conditions, delivery of
materials, equipment available, size of the building, and the
amount of riveting, bolting, and welding required.

12–3 Structural Metal Framing

The metals used for the framing of a structure primarily
include wide flange beams (W series), light beams, I-beams,
plates, channels, and angles. The wide flange shapes are the

most commonly used today and are designated as shown in

Figure 12.1.

Special shapes and composite members require cus-

tomized fabrication and should be listed separately from the

standard mill pieces. The estimator needs to be meticulous

when quantifying each size and length. It is also a good prac-

tice to check not only the structural drawings, but also the

sections and details. The specifications should include the

fastening method required and the drawings of the fastening

details.

Estimating. Both aluminum and steel are sold by weight,

so the takeoff is made in pounds and converted into tons.

The takeoff should first include a listing of all metals

required for the structure. A definite sequence for the takeoff

should be maintained. A commonly used sequence is

columns and details, beams and details, and bracing and

flooring (if required). Floor by floor, a complete takeoff is

required.

Structural drawings, details, and specifications do not

always show required items. Among the items that may not

be shown specifically, but are required for a complete job, are

various field connections, field bolts, ties, beam separators,

anchors, turnbuckles, rivets, bearing plates, welds, setting

plates, and templates. The specification may require confor-

mance with American Institute of Steel Construction (AISC)

standards, with the exact methods to be determined by the

fabricator and erector. When this situation occurs, a complete

understanding is required of the AISC and code require-

ments to do a complete estimate. Without this thorough

FIGURE 12.1.Wide Flange Beam Designation.