Estimating Structural Steel for Construction Projects

Some Things to Keep in Mind When You're Estimating Structural Steel

Building frame
••• Image Source/Getty Images

Structural steel prices can vary widely, even just from one day to the next. Considering that major construction projects take months to years to complete, failure to account for potential fluctuations across the proposed time span of the project can throw your budget and the entire project into a tailspin. 

Having a good and accurate estimate is crucial to competitively bidding and winning major projects, but unexpected purchase prices for the steel can whittle away at your bottom line at the end of the road, compromising the value of any win to your own bottom line.

Here are a few tips and some examples on how to arrive at the best estimate for structural steel.

Some Things to Keep in Mind 

Material purchase location and quantity being purchased are central considerations when estimating structural steel. Warehouse prices generally apply to small orders, while mill prices apply to large orders, and pricing for each respective type of outlet varies. 

Keep in mind that prices offered by a supplier or manufacturer are quoted as of the time of delivery, which means future deliveries are subject to the same laws of fluidity in pricing. Incorporating an escalation clause into a contract to deal with unexpected rising material costs may help absorb any increases. The framing system of a building typically contributes a minimum 10-12 percent -- sometimes more -- of the total building cost.

The Estimating Procedure

Structural steel is normally priced by weight, so having a firm idea of what structural sections will be used and the meaning of the lettering of each section is important for developing an accurate estimate.

For example, the standard method for specifying the dimensions of an American Wide Flange Beam is W 6 x 25, which is 6 inches deep with a weight of 25 pounds per foot.

  • Prepare your takeoff by grouping the steel by its grade.
  • Group your material per section or member type.
  • Continue grouping by method of tied connection.
  • Group structural steel by its location on the project.
  • Maintain sequence of takeoff by columns and details.
  • Specify the beams and details per floor.
  • Take off quantities for bracing and flooring under a separate area.
  • Remember to estimate the quantities of plates, connectors, and accessories.

You might consider listing the materials in your design on a table like the one provided below. Complete the table with the type of section, quantity used, length of pieces, total length required for each particular section, and weight per linear feet. Once completed, the last column will give you a sum estimate of how many pounds of steel are necessary for your project.  

Computing Structural Steel Weight

Properties
MaterialSectionNumberLength(ft)Total LengthWt/FtTotal Wt(Pounds)
W 14 X 132120201322640
W 14 X 120130301203600
W 16 X 40520100404000
W 27 X 9413030942820
W 18 X 5023060503000
W 14 X 431202043860
W 18 X 8431545843780
W 14 X 10981512010913080
W 24 X 6813434682312
W 16 X 261252526650