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1 hour exterior wall

R

Robert

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Pinole, CA
New wall less than 5' from property line (single family residence). The exterior is stucco and interior is 5/8" type X gyp. for a 1 hour rating each side as req'd. by R302.1 (unsprinklered). Per the attached pic...what happens where the wall is interrupted by the floor joists (or ceiling joists in the attic)? Will I need to use 5/8" type X on the ceilings too? If so, what happens in the crawlspace where the exposed wall framing is vulnerable? If this was a cripple wall in the crawlspace, would that have to be protected? I seem to recall a job where I installed 4x blocking in the crawlspace perimeter to achieve a 1 hour equivalent (similar to heavy timber) but don't know where that is in the code. Thanks.
 

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I would say yes to all, the entire exterior needs to be 1-HR. And yes,someone was reaching with the 4X blocking. JMHO

Any chance of changing joist direction to parallel? So it does not have to interrupt the separation?
 
Assuming without 13D, IMO in the IRC platform construction the horizontal assembly is not considered a wall and therefore the space between the floor/ceiling isn't required to be protected.
However the exterior side of the horizontal platform is a portion of the exterior wall.
 
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This is from Table 302.1.(1): 1 hour—tested in accordance with ASTM E119 or UL 263 with exposure from both sides

This is from a recent project:




I agree with Francis and furthermore, 2X eave blocks, rim joists and blocking between floor joists are all legitimate fire blocking.

The cripple wall that you asked about is a twist that I have not encountered. I suppose that an ANSI E119 or UL263 listed assembly would require protection on both sides.
 
Fatboy...if the joist direction was to change, are you relying on the wood of the joist to protect the wall? This is similar to what was done on another job, however AHJ wanted 4x as it was the wood thickness that gave the 1 hour equivalency.

I tend to agree with Francis that the floors/roof are perpendicular to the required fire resistance and therefore exempt. However in the CBC (not the CRC) there is the requirement that the supporting construction must also be protected (cripple walls included) so I'm wondering if the same could apply here.
 
It all depends on how the exposing building face is defined under your code, in ours it is defined as the area of the wall from grade to the highest ceiling. So in our application, floor joists - yes, attic - no.
 
tmurray said:
It all depends on how the exposing building face is defined under your code, in ours it is defined as the area of the wall from grade to the highest ceiling. So in our application, floor joists - yes, attic - no.
Click to expand...

Thanks. In CRC, the definition of exterior wall includes "peripheral edges of floors, roof and basement kneewalls". Am I correct that the peripheral edge of floor in this case will be the exterior face only? Also, our 1 hour wall protection is required on both faces (interior and exterior)...which is why I was asking about the ceiling and floor finish....but going back to the assumption that the perpendicular elements (platformed framed floors) are not part of the definition of "exterior wall" ....(just the peripheral edge) then it sounds like the floor and ceiling finishes are exempt?
 
"Fatboy...if the joist direction was to change, are you relying on the wood of the joist to protect the wall? This is similar to what was done on another job, however AHJ wanted 4x as it was the wood thickness that gave the 1 hour equivalency."

If the direction were to change, the interior finish would be uninterrupted.
 
Robert said:
Thanks. In CRC, the definition of exterior wall includes "peripheral edges of floors, roof and basement kneewalls". Am I correct that the peripheral edge of floor in this case will be the exterior face only? Also, our 1 hour wall protection is required on both faces (interior and exterior)...which is why I was asking about the ceiling and floor finish....but going back to the assumption that the perpendicular elements (platformed framed floors) are not part of the definition of "exterior wall" ....(just the peripheral edge) then it sounds like the floor and ceiling finishes are exempt?
Click to expand...
That is not the way I would interpret it. Ceilings and floors should not require any protection. The protection should extend through the concealed spaces (i.e. between the floor and roof joists) in order to maintain protection. The local AHJ may decide to accept rating of the ceiling and floors in lieu of the wall rating though.

There is certainly an argument to be made on the crawlspace and attic given the fire load of these areas may not have depending on the use of the building. However, this would likely require a fire engineer to make the case.
 
Following through with your reasoning, if the floor/ceiling joist concealed space between the exterior walls needs 1 hour protection, how would you achieve that? What thickness fireblocking will get 1 hour and is that in the code? This is where I was allowed to use 4x blocking on another job, but that was CBC (where the supporting construction needed to be rated in addition to the wall).
 
@ ~ @

Robert,

Isn't the intent to protect all combustibles on an exterior wall,
if less than 5 ft. from the property line, ...even access to
concealed spaces, and regardless if the framed elements are
perpendicular to the wall or parallel to it ?

@ ~ @
 
North star, I don't know. Walls perp. to property line do not need one hour protection even if closer than 5', which is why I am still unsure about the floor and ceiling joist spaces, per my original post. But if I err on the side of caution and decide to make those spaces comply with 1 hour, how do I do it? There is 2x fireblocking at the exterior of each concealed floor and ceiling joist bay. (either as a rim joist or as structural blocking, which I drew on my attachment)...but that does not fully protect the cavity.
 
Robert said:
North star, I don't know. Walls perp. to property line do not need one hour protection even if closer than 5', which is why I am still unsure about the floor and ceiling joist spaces, per my original post. But if I err on the side of caution and decide to make those spaces comply with 1 hour, how do I do it? There is 2x fireblocking at the exterior of each concealed floor and ceiling joist bay. (either as a rim joist or as structural blocking, which I drew on my attachment)...but that does not fully protect the cavity.
Click to expand...

Robert, don't know about CA, this assembly detail would be a fire area separation wall such as Fire Barriers (Shaft Walls) or even Fire Walls reference in the IBC.

707.5 Continuity. Fire barriers shall extend from the top of the foundation or floor/ceiling assembly below to the underside of the floor or roof sheathing, slab or deck above and shall be securely attached thereto. Such fire barriers shall be continuous through concealed space, such as the space above a suspended ceiling.

Area Separation Wall.JPG
 
A crawlspace is not include in the definition of an exterior wall. How much fuel loading is in a crawlspace? l would say a crawlspace wall is not required to have a fire rating from the inside.

IRC
EXTERIOR WALL. An above-grade wall that defines the exterior boundaries of a building. Includes between-floor spandrels, peripheral edges of floors, roof and basement knee walls, dormer walls, gable end walls, walls enclosing a mansard roof and basement walls with an average below-grade wall area that is less than 50 percent of the total opaque and nonopaque area of that enclosing side.

R302.1 Exterior walls.
Construction, projections, openings and penetrations of exterior walls of dwellings and accessory buildings shall comply with Table R302.1(1); or
 
ICE said:
This is from Table 302.1.(1): 1 hour—tested in accordance with ASTM E119 or UL 263 with exposure from both sides

This is from a recent project:




I agree with Francis and furthermore, 2X eave blocks, rim joists and blocking between floor joists are all legitimate fire blocking.

The cripple wall that you asked about is a twist that I have not encountered. I suppose that an ANSI E119 or UL263 listed assembly would require protection on both sides.
Click to expand...


No soffit venting? How is roof ventilation being handled?
 
Francis: Thank you. Your detail shows what looks like a 2 hour assembly and a 2x6 wall and most importantly is showing 4-2x blocks at the floor joist/wall intersection...the area that I am inquiring about. Can I make an assumption that a 1 hour assembly would then require 3-2x blocks at those locations (basically to fill up the width of the wall at the floor assembly)?

Mtlogcabin...I agree. In my case, the foundation wall goes up to the bottom of floor framing so no cripple wall to worry about.

Steveray, I'm not familiar with that detail but IMHO the soffit should breathe. I have uncovered exterior double sided stucco walls that are completely rotten in less than 10 years...the result of no venting. CRC allows combustible projections up to 2' from property line IF blocking is provided at top plate to underside of roof OR if gable vents are not provided in the attic, so perhaps the OP can eliminate the stucco at the soffit if he falls into this category.
 
@ ~ @ ~ @

Robert,

In looking around on "the webby", apparently there are some intumescent coated,
metal type soffitt vents that could be installed to provide ventilation to the attic
and resist the the entrance of hot gases & embers to the attic spaces.
See this Link to one type of product:
http://www.guntermfg.com/index_files/Eave.pdf#page=1&zoom=auto,787,1540

They also have a demonstration video:
Some other web sites [ recommend ] coating the framing with a fire rated
intumescent product, ...adding stucco, ...5/8" gyp. board & additional wood
blocking to achieve the 1 hr. fire rating........Also, in some applications,
re-orienting the roof framing so that there are no soffitts on the property
line side might be an option.

IMO, A combination of these products and efforts could produce the "required"
1 hr. rating.


@ ~ @ ~ @
 
Great links. Francis, I like the look of that...and framers don't have to baffle the insulation at the edges (though here in CA would prob. need raised heel trusses so the insulation does not get pinched). Looks like a Coravent product but don't see it on their website?
 
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