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Join Date: Jun 2009
Posts: 14

# Calculating Fire Wall Resistance

11/04/2009 1:41 PM

How do I calculate the fire rating of an existing wall? The wall consists of 2x6 studs with insulation. On one side is 1" of sheetrock. On the other side is 1-1/4" of wood siding with 3/4" plaster over it. This produces an overall wall width of 8-1/2". I need a two-hour minimum fire rated wall.

The sheetrock gives 40 minutes, and the plaster 50 minutes.

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#1

### Re: Calculate wall fire resistance

11/04/2009 1:46 PM
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Join Date: Mar 2007
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#3

### Re: Calculate wall fire resistance

11/04/2009 1:53 PM
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Join Date: Apr 2009
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#2

### Re: Calculate wall fire resistance

11/04/2009 1:50 PM

One could pore over the UBC and IBC tables for a considerable time, and you would not find that particular construction listed as a fire resistive barrier. In other words, that construction is not a 'Fire Wall'.

post script: "Sheetrock" is a registered trademark of the United States Gypsum Corporation. Generic term for the product is Gypsum Drywall or Wallboard. Sheetrock is a generic term often used (compare with 'Kleenex') to represent the material, but USG is known for vigorous protection of their trademark.

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#4

### Re: Calculating Fire Wall Resistance

11/04/2009 11:58 PM

two hour firewall

or dbl layer of 5/8" type "X" drywall screwed to studs and tape/mudded

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