Steel in construction is measured in various ways, depending on the type of steel and its application. This ensures accuracy for design, fabrication, and material ordering.
Different forms of steel used in building require different measurement standards.
Measurement of Thin Steel Products (Sheets, Coils, Tubes, Wiring)
For thin steel products like sheets, coils, tubes, and wiring, measurement is often done using Gauges.
- Gauges (sometimes spelled “gages” and abbreviated “GA”) are a standardized method of measuring and categorizing thin steel products such as sheets, coils, tubes, and wiring.
- As the gauge number increases, the material thickness decreases in an inverse relationship. For example, 20-gauge steel is thinner than 10-gauge steel. This system provides a quick way to refer to specific thicknesses commonly used in various applications like metal roofing, siding, and ductwork.
Here's a simplified example of how gauge relates to thickness (exact measurements can vary slightly by standard, like U.S. Standard Gauge for sheet steel):
| Gauge Number | Approximate Thickness (Inches) | Approximate Thickness (mm) |
|---|---|---|
| 10 GA | 0.1345 | 3.416 |
| 14 GA | 0.0747 | 1.90 |
| 20 GA | 0.0359 | 0.912 |
| 26 GA | 0.0179 | 0.455 |
Measurement of Structural Steel
Structural steel, used for frameworks and load-bearing elements (like I-beams, H-beams, channels, and angles), is primarily measured by its dimensions, cross-sectional properties, and weight.
- Dimensions: Beams and columns are specified by standard designations that indicate their shape, depth, and weight per unit length (e.g., W 10x33 refers to a Wide Flange beam approximately 10 inches deep weighing 33 pounds per linear foot).
- Weight: Steel is often purchased and estimated by weight (pounds or kilograms), calculated from the volume and density based on its dimensions and length.
- Grade: The steel's grade (e.g., ASTM A992, A36) specifies its material properties, such as yield strength and tensile strength, which are crucial for structural calculations but not a physical measurement of size.
Measurement of Rebar (Reinforcing Steel)
Rebar, used to reinforce concrete, is typically measured by its diameter or a numbering system that relates to its diameter.
- In the United States, rebar is commonly specified using a # system (e.g., #3, #4, #5 rebar). The number generally corresponds to the diameter in eighths of an inch (e.g., #4 rebar is 4/8 or 1/2 inch in diameter).
- In other systems (like metric), rebar is specified directly by its diameter in millimeters (e.g., 10mm, 12mm, 16mm rebar).
- Rebar is also specified by its grade, indicating its yield strength (e.g., Grade 60 implies a minimum yield strength of 60,000 psi).
- It is purchased and delivered based on length and total weight.
Measurement of Other Steel Products
Other steel products in construction are measured according to their form:
- Steel Pipes and Tubing: Measured by outer diameter (OD), wall thickness (often using schedules), and length.
- Steel Plates: Measured by thickness, width, and length.
- Fasteners (Bolts, Nuts, Screws): Measured by diameter, length, thread pitch, and grade.
In summary, steel measurement in construction is not a single method but depends on the specific product, using standards like gauge for thin materials, dimensional and weight specifications for structural members, and diameter/numbering systems for rebar.
