Cement Board and 5/8 Inch Drywall Fire Rating

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Question

Would you please tell me how long cement board/"c" board is fire rated for and how long 5/8 inch drywall is fire rated for?

Answer

Type "X" drywall is rated for one hour. This is 5/8 inch and it really depends on the entire package for that rating. For instance, using metal studs would/could give you more time than wood studs. Typically, Type "X" is rated for one hour. Doubling the layers will result in a two hour fire rating.

This "c" board is certified by each manufacturer with UL control. Generally, a rate of "A" is applied. Think of the three types of fire classifications ABC. "A" being paper. Each manufacturer has their own specificatons. The problem with "c" board is that the trapped moisture, when heated fast, will expand and blow out. Depending upon your application, use the Type "X".



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