Something has been troubling me. I can’t tell you how many times I’ve seen Type X panels used instead of Type C panels (or vice versa) in fire-resistant construction. I even saw a sell sheet from a manufacturer recently promoting how their lightweight Type X boards were one of the only lightweight boards that is Type X rated for walls, beams, columns and CEILINGS. The total disregard for the need for Type C panels in ceilings is so common it’s unbelievable; and I think it’s happening far more than anyone notices.
It’s crucial for contractors to understand the difference between these two panels and communicate when they aren’t used correctly. Why is this such an important topic? Because the integrity of the building and the safety of its occupants are at stake in the event of a fire.
Over the past 30 or so years, the use of uninsulated floor and ceiling assemblies (where Type X can be used) has dramatically declined. Nowadays, almost all floor and ceiling assemblies require Type C for the proper level of fire and acoustical performance.
Each panel addresses different requirements within a building and should be used in those ways. Whereas 5/8” Type X is the most economical gypsum panel for walls where a one-hour (or more) fire rating is required, Type C should rarely be used on walls because its full fire performance isn’t achieved when installed vertically. Type C panels will continue to be used in most ceiling applications requiring insulation.
One of the main reasons these panels are so often misapplied is that there’s no visual differentiation between the boards. Even the difference in the products’ name is subtle and could be overlooked. Accurately identifying a panel is challenging at best and pretty much impossible after it’s hung and the joints are covered. That’s why I’m glad to see that USG is starting to print UL designations in the field of its panels. This will make panels more identifiable for contractors during installation, and code officials during inspections.
Type C panels are also typically more expensive (roughly 10% more), which is probably the biggest reason contractors use Type X instead of C. But imagine the cost of having to repair an entire project after an inspector finds the error. No thanks.
I encourage you to work with your distributor to make sure that Type X and Type C panels are specified and used correctly in every project, and to keep an eye out for the field printing on your USG panels. I’m hoping we’ll see much less of this rampant misuse of Type X where C is called for, and make sure that the level of fire resistance is where it needs to be.
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