Structural Steel Span and Spacing

One-Way Systems

Span: 20'-0"-30'-0" typ.

Spacing: 4'-0"-15'-0" (dependent on metal decking span and load)

Wide Flange Beams

Span: 20'-0" - 60'-0"

Spacing: (dependent on metal decking span and load)

Open-Web Joists

Span: 10'-0" - 90'-0"

Spacing: 16"-6'-0" (dependent on metal decking span and load)

Light-Gauge Steel Joists

Spans

6" Joist: 10'-0"-14'-0"

8" Joist: 12'-0"-18'-0"

10" Joist: 14'-0"-22'-0"

12" Joist: 18'-0"-26'-0"

Steel Rules Of Thumb

Steal Beams and Girders

Beam Depth = span (ft)/20 (take the span of your beam in feet and divide the number by 20)

Girder Depth = span (ft)/15 (take the span of your beam in feet and divide the number by 15)

Beam Width = 1/2 to 1/3 Depth (take the depth of your beam or girder and multiply it by .5 or .33)

Light-Gauge Steel Joists

Joist Depth = span (inches)/20

(take the span of your joist in inches and divide the number by 20)

Metal Decking

Decking Depth = span (inches)/24

(take the span of your joist in inches and divide the number by 20)

Decking Span = 1'6" - 16'-0" depending on decking type

The above calculations are rules of thumb thus they do not take in to account LRFD (load resistance factor design). Consult a structural engineer or architect for load sizes, fire ratings, and other building code information.