# 1hr fire rated assembly question



## platinumaa (Apr 24, 2020)

hello all, 1st post here in awhile. i am remodeling a quadplex in florida. we installed new 4/12 slope 2x4 pre-eng wood truss roof w/ plywood sheathing and standard shingles. we were suppose to install fire treated plywood 48" on each side of the firewall but it didnt happen. we now need a 1hr UL detail. anyone have a ul detail they can suggest that we can use? ive been searching for awhile but cant find anything. i need it to extend down from ridge 48" each direction with 5/8" gypsum secured to bottom of existing wood truss top cord. and blocked off perpendicular with a 2x4 (or something). if not, any other assembly that would work? i could use a spray assembly but trying to use the material we have onsite if possible

thanks for the help!


----------



## cda (Apr 24, 2020)

You have a code compliant one hour wall??

And you were supposed to have four feet fire rated something on each side of that wall ??

Is that the picture ?


----------



## platinumaa (Apr 24, 2020)

correct. u305 fire rated wall, 1hr. we were suppose to have fire treated plywood extending 48" down from ridge on each side


----------



## cda (Apr 24, 2020)

platinumaa said:


> correct. u305 fire rated wall, 1hr. we were suppose to have fire treated plywood extending 48" down from ridge on each side




Just put type x drywall up there

like in the old days


----------



## platinumaa (Apr 24, 2020)

LOL.. i tried that. they want a UL detail. even tried to secure fire treated plywood to bottom of existing plywood.. no go


----------



## cda (Apr 24, 2020)

platinumaa said:


> LOL.. i tried that. they want a UL detail. even tried to secure fire treated plywood to bottom of existing plywood.. no go




Ok tell them to provide code reference,,, requiring it


----------



## cda (Apr 24, 2020)

Do you have the code reference to post

code book and year edition


----------



## RLGA (Apr 24, 2020)

Look at Section 706.6, Exception 4.

If Items 4.1 and 4.2 are met, then all you have to do is comply with the prescriptive requirement of Item 4.3--there is no need to find a UL assembly.


----------



## platinumaa (Apr 24, 2020)

i dont, but i will email and ask


----------



## RLGA (Apr 24, 2020)

Nevermind, I missed the FRT wood part.


----------



## cda (Apr 24, 2020)

The wings I don’t think have to be one hour 

If you would have put the correct decking there,,,,

I don’t think it is one hour rated


----------



## cda (Apr 24, 2020)

platinumaa said:


> i dont, but i will email and ask




This is FBC should be about same in IBC

Look at 2&3



*706.4.1 Townhouse fire separation*




[paste:font size="5"]*townhouse shall be considered a separate building and shall be separated from adjoining townhouses by a party wall complying with Section 706.1.1 or by the use of separate exterior walls meeting the requirements of Tables 601 and 602 for zero clearance from property lines as required for the type of construction. Separate exterior wallsshall include one of the following: 
*

*A parapet not less than 18 inches (457 mm) above the roof line. *
*Roof sheathing of noncombustible material or fire retardant treated wood, for not less than a 4-foot (1219 mm) width on each side of the exterior dividing wall. *
*One layer of 5/8-inch (15.9 mm) Type X gypsum board attached to the underside of roof decking, for not less than a 4-foot (1219 mm) width on each side of the exterior dividing wall. *
*


*


----------



## RLGA (Apr 24, 2020)

Look at UL I502, System A. This does require metal studs, though, but you could install between the trusses with the bottoms flush with the bottom of the rafters, and then run the gypsum continuously from ridge to exterior wall. At the edge of the 4 feet, turn up the gypsum board toward the deck.

See if they'll accept that.


----------



## platinumaa (Apr 24, 2020)

thanks for above. i think quadplex is multi-family. would that still apply? but this is a good start


----------



## platinumaa (Apr 24, 2020)

the UL I502 i believe is for a 2x10 joist system. we have a 2x4 wood truss. thanks though


----------



## cda (Apr 24, 2020)

platinumaa said:


> thanks for above. i think quadplex is multi-family. would that still apply? but this is a good start



Should,,,  or similar that applies 

Need to see what code section ahj comes up with.


----------



## RLGA (Apr 24, 2020)

platinumaa said:


> the UL I502 i believe is for a 2x10 joist system. we have a 2x4 wood truss. thanks though


UL I502 is a membrane system using 6" metal studs (https://iq.ulprospector.com/en/profile?e=14122). The system requires at least 3 inches of insulation above the studs, so maybe fill the space between the rafters with the insulation and then install the metal studs continuously under the rafters.


----------



## cda (Apr 24, 2020)

Missed by one:::

# 2, but it seems like they would allow the decking to be covered underneath, by a non combustible material..

      AND it does not say the noncombustible has to be one hour!!!!!!!!!



CHECK against your book

*706.5 Horizontal Continuity*

_Fire walls _shall be continuous from _exterior wall _to _exterior wall _and shall extend not less than 18 inches (457 mm) beyond the exterior surface of _exterior walls_.
Exceptions:

_Fire walls _shall be permitted to terminate at the interior surface of combustible exterior sheathing or siding provided the _exterior wall _has a _fire-resistance rating _of not less than 1 hour for a horizontal distance of not less than 4 feet (1220 mm) on both sides of the _fire wall_. Openings within such _exterior walls _shall be protected by opening protectives having a _fire protection rating_ of not less than 3/4 hour.
_Fire walls _shall be permitted to terminate at the interior surface of noncombustible exterior sheathing, exterior siding or other noncombustible exterior finishes provided the sheathing, siding or other exterior noncombustible finish extends a horizontal distance of not less than 4 feet (1220 mm) on both sides of the _fire wall_.
_Fire walls _shall be permitted to terminate at the interior surface of noncombustible exterior sheathing where the building on each side of the _fire wall _is protected by an _automatic sprinkler system _installed in accordance with Section 903.3.1.1 or 903.3.1.2.


----------



## cda (Apr 24, 2020)

OK maybe I missed it again, I was holding my hand wrong:::

Check against your book::

*706.6 Vertical Continuity*

_Fire walls _shall extend from the foundation to a termination point not less than 30 inches (762 mm) above both adjacent roofs. 
Exceptions:

Stepped buildings in accordance with Section 706.6.1.
Two-hour fire-resistance-rated walls shall be permitted to terminate at the underside of the roof sheathing, deck or slab, provided:
The lower roof assembly within 4 feet (1220 mm) of the wall has not less than a 1-hour _fire-resistance rating _and the entire length and span of supporting elements for the rated roof assembly has a _fire-resistance rating _of not less than 1 hour.
Openings in the roof shall not be located within 4 feet (1220 mm) of the_ fire wall_.
Each building shall be provided with not less than a Class B roof covering.

Walls shall be permitted to terminate at the underside of noncombustible roof sheathing, deck or slabs where both buildings are provided with not less than a Class B roof covering. Openings in the roof shall not be located within 4 feet (1220 mm) of the _fire wall_.
*In buildings of Type III, IV and V construction, walls shall be permitted to terminate at the underside of combustible roof sheathing or decks, provided: *
* There are no openings in the roof within 4 feet (1220 mm) of the fire wall,*
* The roof is covered with a minimum Class B roof covering, and*
* The roof sheathing or deck is constructed of fire-retardant-treated wood for a distance of 4 feet (1220 mm) on both sides of the wall or the roof is protected with 5/8-inch (15.9 mm) Type X gypsum board directly beneath the underside of the roof sheathing or deck, supported by not less than 2-inch (51 mm) nominal ledgers attached to the sides of the roof framing members for a distance of not less than 4 feet (1220 mm) on both sides of the fire wall.*

In buildings designed in accordance with Section 510.2, _fire walls_ located above the 3-hour _horizontal assembly _required by Section 510.2, Item 1 shall be permitted to extend from the top of this _horizontal assembly_.
Buildings with sloped roofs in accordance with Section 706.6.2.


----------



## cda (Apr 24, 2020)

From the good book::

See figure 13

And Vertical continuity # 4 



https://specsandcodes.typepad.com/the_code_corner/2011/11/fire-walls.html


----------



## RLGA (Apr 24, 2020)

cda, that is for exterior walls. The section is for _horizontal continuity_, which means from one end of the fire wall to the other end. For this particular application, you have to look at the requirements for _vertical continuity_.


----------



## RLGA (Apr 24, 2020)

cda, sorry, you changed it as I was typing my response.


----------



## RLGA (Apr 24, 2020)

cda said:


> OK maybe I missed it again, I was holding my hand wrong:::
> 
> Check against your book::
> 
> ...


cda, you're correct. I was right in my first post in this thread, but I didn't remember, nor looked close enough to see, that there is an "or" embedded in there. If you apply the gypsum board as prescribed by Item 4.3, then a UL assembly is not required. That should simplify things greatly.


----------



## cda (Apr 24, 2020)

I was holding my hand wrong,,,

And H comes before V in the alphabet and code book.


----------

