Exterior Wall Assembly


jrboter
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Can someone help me with a plan check comment I have received regarding an exterior wall that is within five feet of the property line. City is asking for the "approved listing number for the 1-hour fire-rated assembly. The approved listing number can be in the form of a GA File # or ESR report #". 

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If you are using stucco, this will work. Do a web search for One Hour Wall assembly and refine your search for exterior side. Basically, you are going to need to use a Class 1 siding material and have a layer of Denseglass or similar over your sheathing. There are some fire rated sheathings that you can use to avoid the extra layer.

 

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UL U387 Wall Assembly one hour with mineral sheets.pdf

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Thank you, much appreciated. I've shown on the plans an exterior wood 2x4 wall with James Hardie lap siding, Tyvek, insulation and Type X gypsum. It seems they want an approved listing # for that wall detail. 

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Take a look at the Calculated Fire Resistant method outlined in the CBC, Chapter 7, 722.6 Wood Assemblies.  It applies to walls up to 1 hour rating.  It essentially allows a way to demonstrate a one-hour wall rating without the need to cite a tested assembly number.  I think this method is often overlooked and is easier.

 

Alternately, Section 721 "Prescriptive Fire Resistance" should have a good assembly I believe.  Table 721.2(2), Item 15.

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Those GA type and ESR type reports are Gypsum Association docs, and won't be any help with your Hardie Plank finished wall.

 

I looked here, in a web page from James Hardie, linking to Warnock Hersey reports of fire-rated wall assemblies faced with Hardie products.  I was in the entry door business (ThermaTru) and we did all our fire door testing at Warnock Hersey labs and they provided reports such as these.

 

I could not find a wall assembly making a 1-hour rating that did NOT have 5/8 GWB (gypsum wall board) on the exterior side of the framing layer.  

 

Recommend you ask the AHJ plans review person if a Warnock Hersey doc will do for your project, where the 1-hour wall is needed, and that you study the information at the link.

https://www.jameshardie.com/product-support/resource-center/technical-documents/fire-wall-assemblies?loc=refresh

 

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