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Vertically continuity of firewall without parapet (706.6)

admiralArchArch

admiralArchArch

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Nov 30, 2018
Messages
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middle earth
We are evaluating a load bearing CMU wall in a existing building as a new firewall between two existing portions of the building. The two structures are completely separate, load bearing CMU on one side, post and beams on the other. The building was built in the mid 70s and features a poured gypsum roof. The firewall will be 2hr rated. The roofs are at the same level (not stepped).

I am having a hard time interpreting the exceptions of 706.6 (2018). Adding a parapet is not feasible, so I'm looking at exceptions 2 or 3. We cannot determine if the existing roof is class B or not but from research the gypsum roof should be at least 1 hr tested from historical data.

That leaves me with exception 2 and 2.1:

The wording of "the entire length and span of supporting elements for the rated roof assembly has fire-resistance rating of not less than 1 hour" is where I'm hung up. Does that mean we need to apply fire resistive material to the entire portion of this building (beams, columns, joist), or just within 4-feet both sides of the firewall? Does only protecting the steel, assuming the roof assembly is 1hr rated, meet the criteria of this exception?
 
First....Why are you putting a firewall in an existing building?


From Commentary:

Exception 2 to this section’s requirement for a parapet
applies to buildings where: a. The maximum
required fire-resistance rating of the fire wall is 2
hours; b. The roof assembly located within 4 feet
(1219 mm) of the fire wall has a minimum fire-resistance
rating of 1 hour (including all supporting elements
and structural members); c. No roof openings
are located within 4 feet (1219 mm) of the fire wall;
and d. The buildings on either side of the fire wall
have a minimum Class B roof covering. The provisions
of Exception 2 are not applicable to buildings
with combustible roof construction where a fire wall is
required to have a fire-resistance rating of 3 hours or
greater. Buildings where the fire wall is required to
have a 3-hour or greater fire-resistance rating must
comply with the general provisions of Section 706.6,
or with Exception 3 or 4 in order to qualify for the parapet
extension exception.
 
The fire wall must be independent of both structures. If the building with the load-bearing CMU collapsed, it would leave the other building exposed. To use the CMU wall as a fire wall, you would need to create a new separate wall between the columns and the existing CMU wall to protect the other building supported only by columns.
 
steveray said:
First....Why are you putting a firewall in an existing building?


From Commentary:

Exception 2 to this section’s requirement for a parapet
applies to buildings where: a. The maximum
required fire-resistance rating of the fire wall is 2
hours; b. The roof assembly located within 4 feet
(1219 mm) of the fire wall has a minimum fire-resistance
rating of 1 hour (including all supporting elements
and structural members); c. No roof openings
are located within 4 feet (1219 mm) of the fire wall;
and d. The buildings on either side of the fire wall
have a minimum Class B roof covering. The provisions
of Exception 2 are not applicable to buildings
with combustible roof construction where a fire wall is
required to have a fire-resistance rating of 3 hours or
greater. Buildings where the fire wall is required to
have a 3-hour or greater fire-resistance rating must
comply with the general provisions of Section 706.6,
or with Exception 3 or 4 in order to qualify for the parapet
extension exception.
Click to expand...

We are putting on a addition that puts us over the allowed SF. This is the best place to put one to create "two buildings".
 
Well....A couple things there....

[A] LOT. A portion or parcel of land considered as a unit.
[A] LOT LINE. A line dividing one lot from another, or from
a street or any public place.

706.1 General. Fire walls shall be constructed in accordance
with Sections 706.2 through 706.11. The extent and location
of such fire walls shall provide a complete separation. Where
a fire wall separates occupancies that are required to be separated
by a fire barrier wall, the most restrictive requirements
of each separation shall apply.
706.1.1 Party walls. Any wall located on a lot line
between adjacent buildings, which is used or adapted for
joint service between the two buildings, shall be
constructed as a fire wall in accordance with Section 706.
Party walls shall be constructed without openings and
shall create separate buildings.
Exceptions:
1. Openings in a party wall separating an anchor
building and a mall shall be in accordance with
Section 402.4.2.2.1.
2. Party walls and fire walls are not required on
lot lines dividing a building for ownership
purposes where the aggregate height and area
of the portions of the building located on both
sides of the lot line do not exceed the maximum
height and area requirements of this code.
For the building official’s review and approval,
the official shall be provided with copies of
dedicated access easements and contractual
agreements that permit the owners of portions
of the building located on either side of the lot
line access to the other side for purposes of
maintaining fire and life safety systems necessary
for the operation of the building.


Or ask for a modification as an existing building to use a fire barrier like the IEBC does for COO?

1011.6.1.1 Fire wall alternative. In other than Groups
H, F-1 and S-1, fire barriers and horizontal assemblies
constructed in accordance with Sections 707 and 711,
respectively, of the International Building Code shall
be permitted to be used in lieu of fire walls to subdivide
the building into separate buildings for the
purpose of complying with the area limitations
required for the new occupancy where all of the
following conditions are met:

Or rate everything....
 
@steveray, IEBC Section 1011.6.1.1 is for changes of occupancy. The OP later stated that the building area situation was due to an addition. Chapter 11 on additions does not offer that type of accommodation.
 
@RLGA, yes correct. Not changing occupancies, and not a party wall. I was not involved in the planning and code strategies for this, simply asked to research this fire wall and detail and went down this rabbit hole. Sounds like they might need to revisit this strategy.
 
admiralArchArch said:
@RLGA, yes correct. Not changing occupancies, and not a party wall. I was not involved in the planning and code strategies for this, simply asked to research this fire wall and detail and went down this rabbit hole. Sounds like they might need to revisit this strategy.
Click to expand...
Add an "ownership line" and then don't put a wall on it at all....What are the use groups?
 
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