Understanding Steel Grating Designations

When searching for steel grating, you’ll likely find numbers like 19W4, 11W4, and 8W4. These are all common designations for industrial and municipal steel grating. These classifications are designed to help you understand the material and configuration of the grating to ensure it meets your application’s needs.

Who Standardizes These Designations?

The American National Standards Institute (ANSI) and the National Association of Architectural Metal Manufacturers (NAAMM) are responsible for standardizing steel grating designations. Their metal bar grating manual highlights which numbers and letters to use when describing steel type, design/construction type, load-bearing capacity, surface pattern, and dimensions.

Breaking Down These Designations

Bar Spacing

The first one or two numbers (such as in 19W4) refer to the bearing bar spacing. This number is measured in sixteenths of an inch. So, in the case of 19W4, the bars are spaced 1 and 3/16 inches apart (19/16).

The bar spacing determines how much load the grating can bear, so it’s critical that you choose a grating with the correct spacing. Wider spacing helps reduce weight but could limit the grating’s load-bearing capacity. Close bar spacing is generally preferred for industrial applications that require a higher capacity, while wider bar spacing is commonly used for cat walks and other light-duty applications.

Construction Type

Next, the letter describes how the grating is constructed. In the 19W4 example, the W stands for welded. Welded grating is created by welding the cross bars to the bearing bars at each intersection and is typically used in high-load environments because it’s strong and rigid.

In addition to welded, there are two other commonly used construction types:

• P: Press-locked, where the cross bars are pressed into notches in bearing bars without welding. They are commonly used in light-duty grating and decorative fencing and are not as heavy-duty as welded grating.
• R: Riveted, where the cross bars are riveted to the bearing bars. This grating type has exceptional strength, so is preferred for mining applications, heavy machinery platforms, and grating in high-load areas.

Cross Bar or Rivet

The next number in the designation refers to the cross bar or rivet spacing, which is measured in eighths of an inch. In the 19W4 example, the 4 means that the cross bars are spaced 4 inches apart, W2 would indicate the cross bars are spaced 2 inches apart, etc. The cross bar spacing helps with load distribution and lateral stability.

Bar Size

After the initial 4-5 number designation, you’ll see dimensions referring to the bar size. This is pretty self-explanatory. If you see 1/4” x 2” inches, this means that the bar is 1/4 inch thick and 2 inches deep. Larger or thicker bars increase the load-bearing capacity.

Surface Pattern

You may also see a surface pattern designation. There are two types: plain and serrated. Plain surfaces are smooth, while serrated surfaces are (you guessed it) serrated. Serrated surfaces provide better traction, so are preferred in wet and/or oily environments. Different manufacturers may use different letters for this, as these aren’t standardized. You may see “P” or “PLN” for plain or “S” or “SER” for serrated.

Material

Lastly, manufacturers may use a material label in the designation. Grating is typically made from either steel, stainless steel, or aluminum. They will be marked as such, so it will be easy to figure out.

Get Help From Laurel Custom Grating

Laurel Custom Crating has been an industry-leading manufacturer of heavy-duty industrial steel bar grating since 1983. If you’re still not sure what type of grating you need for your application, please contact us today to speak with one of our specialists.