Estimating Structural Steel for Construction Projects

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

Image Source/Getty Images

Structural steel prices can vary widely, even from just one day to another. Considering that major construction projects take much more time than just a few days, it can throw your budget and your entire project into a tailspin if you don't accurately estimate what the necessary steel will cost somewhere down the road. 

Having a good and accurate estimate is crucial to being the low bidder, the one who typically gets the job, but you don't want an unexpected purchase price for the steel to whittle away at your bottom line at the end of the road, either.

Even worse, you could potentially lose money on the project. There's low...then there's low. 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 

You must consider the location of where the material is purchased and the quantity that is being purchased when you're estimating structural steel. Warehouse prices will generally apply to small orders, while mill prices will apply to large orders. And warehouse prices and mill prices can be different. 

You'll also want to keep in mind that prices offered by a supplier or manufacturer are quoted as of the time of delivery. You might have to incorporate escalation clauses into a contract to deal with unexpected rising material costs. The framing system of a building typically contributes from 10 percent up to 12 percent or even more of the total building cost.

The Estimating Procedure

Structural steel is normally priced by weight, so you must have a firm idea of what sections you're going to use and the meaning of the lettering of each structural section.

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 this one provided here. Complete the table with the type of section, the quantity used, the length of pieces, the total length required for each particular section, and the weight per linear feet. When you're finished, the addition of the last column will give you an 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