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How To Use Steel I-Beams & Girders

When building a home or an addition it is not necessary to frame the house completely in lumber. Steel beams and girders can be used to span longer distances with less chance of bending than might occur using wood beams. Steel beams are often used in place of heavy wooden girders in the framing of floor systems.

A 6 inch deep steel section can substitute for a wooden girder 14 inches deep, thus saving headroom.

The following table gives the allowable loads for steel beams and it indicates two different types of cross sections. The most popular I-beam is designated on the table as an "S" section, as shown in Figure 1. The "S" stands for slim. The "W" designation refers to a steel section with wider flanges, as shown in Figure 2, than the "S" section.

"S" style I-beam

Figure 1 - "S" style I-beam

"W" style I-beam

Figure 2 - "W" style I-beam

Safe Loads In Pounds For Steel I-Beams & Girders

Style

Size

Span

10'

12'

14'

16'

18'

20'

S

6" X 12.5"

8,700

7,300

6,200

6" X 17.25"

10,400

8,700

7,400

7" X 17.5"

13,300

11,100

9,500

8,300

8" X 18.4"

17,100

14,200

12,200

10,700

9,500

8,400

8" X 23"

19,300

16,100

13,800

12,000

10,700

9,600

W

8" X 17"

21,000

17,000

15,000

13,000

10" X 21"

33,000

28,000

24,000

21,000

18,000

15,000