This table shows Factory Mutual’s maximum allowable spans for each steel roof deck type and gauge, based on multiple long span metal deck conditions (2 or more). In other words, each sheet must rest on at least three supports that are approximately equally spaced. (See figure1)
The table lists the three 1.5 inch deep steel roof deck profiles in ascending strength, followed by the 3 inch deep profile. As you might expect, the allowable spans increase as material thickness increases (gauge number goes lower). What you may find surprising is the difference in allowable spans for the first three profiles, even though they are all 1.5 inches deep with ribs 6 inches on center! If you would like us to help you determine the right profile and gauge for your next project, particularly for Type A roof deck, please give us a call. We’re always happy to help!