# Type C Sheetrock



## cda (Mar 10, 2017)

I know there was discussion awhile back about

Type C Sheetrock vs type X

Just seeing anymore pro/con on Type C?
Or anything else about C??


Do you see it used much?

Anything about not listed for vertical use??


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## Paul Sweet (Mar 10, 2017)

If I remember correctly, 1/2" type C can provide a 1 hour rating, but type X requires 5/8" for a 1 hour rating.

Type X is generic, type C may be proprietary.


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## RLGA (Mar 10, 2017)

Paul Sweet said:


> Type X is generic, type C may be proprietary.


Bingo! Type C must be per tested assembly. Type X can be used in generic assemblies and when using calculated methods.


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## fatboy (Mar 10, 2017)

And we have found that it is not readily available, hence the default to Type X.


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## mark handler (Mar 10, 2017)

USG invented USG Sheetrock® Brand Firecode® C Gypsum Panels, which provides even greater fire resistance than Type X. As with the Type X panels, the core of the Type C panels contains glass
fibers, only in a much higher percent by weight. In addition to the greater amount of glass fiber,
the core of the Type C panels also contains vermiculite, which acts as a shrinkage-compensating
additive that expands when exposed to elevated temperatures of a fire. This expansion occurs
at roughly the same temperature as the calcination of the gypsum in the core. It allows the core
of the Type C panels to remain dimensionally stable in the presence of fire, which in turn allows
the panels to remain in place for a longer period of time even after the combined water has been
driven off.
https://www.usg.com/content/dam/USG...pe-x-and-type-c-white-paper-en-usa-WB2605.pdf


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## cda (Mar 10, 2017)

Thoughts :::


"""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."""



http://www.lwsupply.com/blog/the-difference-between-type-x-and-type-c.html


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## tim walocha (Apr 5, 2017)

Actually the vermiculite either slows the release of water or increases the amount of latent water in the gypsum board.  The failure point of wallboard occurs afters the latent water is removed by heat or boiled off.  More water or slower release of latent water equals more time.  This is straight from a UL Fire Protection Engineer.  Otherwise ditto everything else above.

As a plan reviewer I see designers specifying fire resistive designs utilizing Type C Board but details and project specification still reflecting type X.

This has got to cause a nightmare in the field when it comes to inspection.


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