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.