# Is this a 1 hour wall?



## nealderidder (Mar 19, 2019)

I'm looking for a 1hr assembly for an exterior wall. Wood frame construction with exterior stucco. The trick is that I'm trying to find something with wood sheathing on the exterior (not DensGlass etc.). I need the rating for type V-A construction (have plenty of fire separation distance). 

Note that in CA section 705.5 requires that the wall be rated from both sides. 

I haven't found a manufacturer's tested assembly but I've heard folks say you can do this via the prescriptive fire resistance section (CBC 721). 

Would you buy this as a 1 hour assembly? Would you require any more info than this?


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## Pcinspector1 (Mar 19, 2019)

nealderidder said:


> Would you buy this as a 1 hour assembly? Would you require any more info than this?



I have to see a tested assembly, but that's just me?

If you haven't, try looking in the (UL) listed fire walls or the latest *Gypsum* *Fire Resistance Design Manual*, I'm still waiting for the latest edition to arrive, the 13th addition may be a bit outdated. 

Maybe some Fire-treated plywood designs?


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## steveray (Mar 19, 2019)

I believe I have seen it with FRT on the outside...But that was a long time ago.....

I would have to do the math on what you show, but it looks reasonable...


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## nealderidder (Mar 19, 2019)

Pcinspector1 said:


> I have to see a tested assembly, but that's just me?



Does that make you a Prescriptive Fire Resistance Denier? 

I've been all up in the UL and GA assemblies but haven't found just the right one yet...


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## Pcinspector1 (Mar 20, 2019)

nealderidder said:


> Does that make you a Prescriptive Fire Resistance Denier?



Not necessarily, if stamped by an engineer I would consider accepting a prescriptive design with calculations. I do like the idea of a wall that's been tested by (UL) or other approved testing lab.

Still waiting on my Gyp system manual, should be here today. Maybe someone on the form can take a peek for you to see if FRT has been added to a design?


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## Pcinspector1 (Mar 20, 2019)

nealderidder, have you gone to Hoover treated wood products, the show a 1-hr exterior wall design that may work?

www.frtw.com


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## nealderidder (Mar 21, 2019)

Pcinspector1 said:


> Not necessarily, if stamped by an engineer I would consider accepting a prescriptive design with calculations. I do like the idea of a wall that's been tested by (UL) or other approved testing lab.



Isn't the idea of the prescriptive designs that they don't require calculations? 721.1 says "...The materials of construction listed in Tables....shall be assumed to have the fire-resistance ratings prescribed therein..."

No testing or calcs required, right?


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## nealderidder (Mar 21, 2019)

Pcinspector1 said:


> nealderidder, have you gone to Hoover treated wood products, the show a 1-hr exterior wall design that may work?
> 
> www.frtw.com




They might have something but my contention is that I can add non-FRT wood sheathing and still meet the code requirement for a 1HR  wall. Footnote "L" to Table 721.1(2) says:

_Wood structural panels shall be permitted to be installed between the fire protection and the wood studs on either the interior or exterior side of the wood frame assemblies in this table...
_
So if I pick 15-1.3 of that table for the exterior half of my wall and 14-1.3 for the interior half I have a 1 HR all. Footnote "L" then allows me to slip in some wood sheathing either behind the stucco or behind the gyp. bd. 

Maybe the FRT products are better now but I remember using sheathing in the past and thinking - wow, this is like using shredded wheat. It seemed like the arsenic or boric acid or whatever soup they used really weakened the panels.

Thank you for the input and ideas!


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## Pcinspector1 (Mar 22, 2019)

I've got to read the footnotes, I believe it would be allowed with the correct length of fasteners. Also footnote "a" allows staples for attaching to wood framing. 

Your case is strengthen by footnote "o" in that table as well.


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## ADAguy (Apr 4, 2019)

staple diameter is not equal to nails? are staples rated for fire resistance to withdrawl?


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## mtlogcabin (Apr 4, 2019)

I suggest you specify the insulation so you get the 15 minutes. You get 20 minutes for the studs. You can get another 15 minutes specking out 19/32 sheathing  and then list the time you get for the specific stucco type and thickness

IBC Table 722.6.2(5)
Add to the fire-resistance rating of wood stud walls if the spaces between the studs are completely filled with
glass fiber mineral wool batts weighing not less than 2 pounds per cubic foot (0.6 pound per square foot of wall surface) or rockwool or slag material wool batts weighing not less than 3.3 pounds per cubic foot (1 pound per square foot of wall surface), or cellulose insulation having a nominal density not less than 2.6 pounds per cubic foot.


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## JCraver (Apr 5, 2019)

You might look at this from the AWC


*2x6 Wood Exterior Wall Passes Fire Test – Added to Fire-Resistance-Rated Wood Assemblies*

To meet new energy requirements, a number of designers have been asking to use asymmetrical exterior wood-frame walls constructed with 2x6 studs spaced at 24 inches on-center with fiberglass cavity insulation. An ASTM E119 1-hour fire resistance test, including the hose-stream component, was successfully completed on this assembly. This new 1-hour fire-resistance-rated assembly was added to the AWC _Design for Code Acceptance (DCA) 3 - Fire-Resistance-Rated Wood Floor and Wall Assemblies_. A free download of the updated _DCA3_ can be found on the AWC website: *http://www.awc.org/codes-standards/publications/dca3*.


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