Fire rating of cement board ?

[Clarence Martin]

Anyone know what the fire rating of 1/2 inch thick cement board would be and if the board is doubled up to 1 inch thick, what is the best way to attach it to a metal surface ?


Thanks,

[John Downey]

Have you tried the manufacturer's website? Usually they list this sort of info for their products and have digital versions of brochures outlining installation techniques.

[Matt Day]

There should also be a UL rated assembly for whatever you're building with it. For instance, there are hundreds of UL rated assemblies for drywall for different manufacturers, thicknesses, types of stud material (metal, wood, etc), and number of sheets. And then there are hundreds of assemblies for penetrations... it gets pretty complicated.
From working in commercial construction, you need a UL rated assembly to make the Fire Marshal happy, if that's what you're trying to do.

[Clarence Martin]

I am trying to fireproof a safe .

[Clarence Martin]

From what I have seen of fireproof safes, the real big difference, besides the cheap air seal around the door, is the addition of a couple of 1/2 inch sheets of drywall.

[John Downey]

From what I have seen of fireproof safes, the real big difference, besides the cheap air seal around the door, is the addition of a couple of 1/2 inch sheets of drywall.

Use gypsum board rather than cement board then. The "fireproofing" effect is that lining the box with gypsum board keeps the insides below the boiling point of water for a period of time due to the energy from the fire being consumed driving water off from the gypsum (leaving anhydrite rather than gypsum). The effect is not open ended, once all the water is gone from the mineral, the temperature inside the safe will rise.

Cement board is non-combustible and slightly insulating, but probably not the right stuff to use.