Most cost-effective fire wall?

[imhotep]

2006 IBC, existing 80' x 250' typical steel-framed building, with wood framed offices and mezzanine above. City had originally thought IIB construction until they learned of the wood construction that had been added inside. Now the owner wants to add another 80' x 150' and is way over square footage limits for VB construction and the city wants a fire wall. The owner wants to install 2 layers of sheetrock to the existing skin, then add a stud wall and 2 more layers of sheetrock on the new side of the studs, thus creating a 2 hour wall. Screws from the inside of the flanges could attach the sheetrock to the studs from the "inside" of the new stud wall and then the sheetrock would no longer be dependent upon support by the existing skin (ave ht 19'). The joints could be overlapped as required and taped, but the tape and finish would be on the inside face of the sheetrock. Is this "close enough" to UL to be acceptable, or is there a better option? Gotta be cheap.

Typical steel framed building: Metal clad exterior - metal girts - steel structural frame? Sounds like a IIIB construction type.

What is the use and occupancy? If mixed occupancy then Separated or Nonseparated?

 

[DwightB]

CodeGeek: I have greater than 30' in all directions, so can take the max 75%, which qualifies the building.

Brudgers: When the local BO learned that wood framed walls and mezzanine floor above had been added, she said, "then it's a VB" and I went along with that. However, with the suggesting by a member here referring to IIIB, a close examination of the code revealed the 0 hr requirements, except for exterior bearing walls (there are none with the steel framed building), and allows "any material allowed by code" for interior elements, no ratings required. I agree that the building satisfies the IIIB requirement. So with a IIIB, I'm allowed enough square footage (with a perimeter increase) that the building qualifies without a fire wall.

Imhotep: Occupancy is S-2, storage of non-flammables on wood pallets (basically an HVAC wholesaler). New addition is assumed will be a similar operation.

 

[brudgers]

CodeGeek: I have greater than 30' in all directions, so can take the max 75%, which qualifies the building. Brudgers: When the local BO learned that wood framed walls and mezzanine floor above had been added, she said, "then it's a VB" and I went along with that. However, with the suggesting by a member here referring to IIIB, a close examination of the code revealed the 0 hr requirements, except for exterior bearing walls (there are none with the steel framed building), and allows "any material allowed by code" for interior elements, no ratings required. I agree that the building satisfies the IIIB requirement. So with a IIIB, I'm allowed enough square footage (with a perimeter increase) that the building qualifies without a fire wall. Imhotep: Occupancy is S-2, storage of non-flammables on wood pallets (basically an HVAC wholesaler). New addition is assumed will be a similar operation.

I take paypal.

 

[Builder Bob]

please define a wall per the building code..... it doesn't exist. the metal panels are not anythiong but a veneer, the purlins that the metal panels attach to are unable to exist without the vertical members that they attach to. the purpose of rating the exterior load bearing walls of a type III buildig is to prevent the exterior walls from collapsing. (Old town USA - fire cuts)

With the intent being to prevent the exterior walls from collapsing, the interpretation from my old building official would require any vertical load bearing component that purliins attached to be to be fire rated for two hours.......... this prevented the installation of pre-engineered metal buildings with wooden interior partitions ---- So I couldn't have have a S-1 17,500 SF two story facility when in essence it is a type V B construction limited to a single story and 9,000 SF...... because the wooden interior partitions may be protected from fire exposure from one side but not the other when placed along the exterior veneer wall of the building.

FWIW, I do not agree witht the classification of the building as a type III building.

 

[syarn]

does the BO have a record of the bldg permit app for the addition of the wood framed walls & mezzanine floor and what the construction type classification was for that work?

 

[DwightB]

Builder Bob: The exterior walls are not supporting the roof. The beams, columns, and purlins are structure that supports the exterior walls and roof. Table 601 says: "Structure, 0 HR", whether Type IIB, IIIB or Type VB, and specifically defines the "structure' to be columns girders, beams trusses

Interior, the wood partitions and mezz floor (Type IIIB allows any material allowed by code on interior) are not part of the building structure.

 

[DwightB]

syarn: NO, that was an illegal construction. There was no permit, the city didn't know about it until now.

 

[Builder Bob]

If the exterior all isn't supporting the roof.... define wall per the building code.

The columns are the support (I agree)

However, what is holding up the purlins and the veneer of the exterior section of the building?

 

[DwightB]

Veneer may be a poor choice of words. Veneer is basically a cosmetic finish surface with no structural ability that is laminated on to a supporting backing. The metal skin of the building has sufficient strength to span the distance between girts, but is not a bearing wall. The skin can be completely removed and the building will still stand. In fact, the skin is the last thing to be applied, unlike a bearing wall, which must be built before the roof or upper levels can be built.

The columns are holding up the purlins and skin, and are specifically excluded from fire rating.

The skin is 30' or greater from adjacent property line, so no requirement there either.

 

[mtlogcabin]

EXTERIOR WALL. A wall, bearing or nonbearing, that is used as an enclosing wall for a building, other than a fire wall , and that has a slope of 60 degrees (1.05 rad) or greater with the horizontal plane.

 

[ggmarch]

wait a second.....just going IIIb doesn't solve the problem that no separation if it's required.....add it up..... a building of 20,000 orig SF plus the 10,000 New SF leaving you with a 30,000 SF building. still an issue and needs a variance IMHO....are there penetrations between old and new?

...... the owner's assembly is not tested therefore, it won't pass muster.....cheapest method....2x6 wall(metal) with double firecode. build section at a time drywall side facing existing bldg, tape joints, tilt in place, brace as required cover inside face with double drywall (X) and repeat. maybe a little more labor intensive is go the UL U336 route.

it's unfortunate, but the new code doesn't like existing buildings. i just got one through after 2 months of going back and forth with the code official about a steel manufacturing plant addition where the existing building didn't fall nice and neatly into the current code therefore any alteration of the building would have made their whole operation illegal and non compliant. the code official granted our claim of both existing S-2 F-2 in a pre-engineered stl building(fit no building type) and the addition F-2 S-2 in a pre-engineerd stl building both as type IIb and no separation required. i totally redesign for the 2 hr independent wall between existing and new and then one day they called and said, they just made it a non-issue. i'm sure a bunch here will find that offensive, but it's within the code official's right to accept reasonable deviations from the code(if they couldn't, there'd be no reason for a variance hearing board and the code book would be 20' thick instead of 3 inches)

 

[mtlogcabin]

Type IIIB S2 allows 26,000 sq ft. He is allowed an increase because of the 30 ft around the building.

If he had 60 ft it could be unlimited

507.2 Nonsprinklered, one story.

The area of a Group F-2 or S-2 building no more than one story in height shall not be limited when the building is surrounded and adjoined by public ways or yards not less than 60 feet (18 288 mm) in width.

 

[Builder Bob]

The metal skin is a veneer - addressed by table 1405.2 and section 1405.11 of the IBC.

The metal skin is a veneer as it does not provide any structural stability to the building..... the purlins and wind/siemic bracing provide the structural support for racking of a structure.

 

[brudgers]

Veneer may be a poor choice of words. Veneer is basically a cosmetic finish surface with no structural ability that is laminated on to a supporting backing. The metal skin of the building has sufficient strength to span the distance between girts, but is not a bearing wall. The skin can be completely removed and the building will still stand. In fact, the skin is the last thing to be applied, unlike a bearing wall, which must be built before the roof or upper levels can be built. The columns are holding up the purlins and skin, and are specifically excluded from fire rating. The skin is 30' or greater from adjacent property line, so no requirement there either.

The correct term is "curtain wall."

 

[brudgers]

wait a second.....just going IIIb doesn't solve the problem that no separation if it's required.....add it up..... a building of 20,000 orig SF plus the 10,000 New SF leaving you with a 30,000 SF building. still an issue and needs a variance IMHO....are there penetrations between old and new? ...... the owner's assembly is not tested therefore, it won't pass muster.....cheapest method....2x6 wall(metal) with double firecode. build section at a time drywall side facing existing bldg, tape joints, tilt in place, brace as required cover inside face with double drywall (X) and repeat. maybe a little more labor intensive is go the UL U336 route. it's unfortunate, but the new code doesn't like existing buildings. i just got one through after 2 months of going back and forth with the code official about a steel manufacturing plant addition where the existing building didn't fall nice and neatly into the current code therefore any alteration of the building would have made their whole operation illegal and non compliant. the code official granted our claim of both existing S-2 F-2 in a pre-engineered stl building(fit no building type) and the addition F-2 S-2 in a pre-engineerd stl building both as type IIb and no separation required. i totally redesign for the 2 hr independent wall between existing and new and then one day they called and said, they just made it a non-issue. i'm sure a bunch here will find that offensive, but it's within the code official's right to accept reasonable deviations from the code(if they couldn't, there'd be no reason for a variance hearing board and the code book would be 20' thick instead of 3 inches)

Probably use area increase for frontage.

 

[DwightB]

Brudgers: Yes, the perimeter increase gives me the additional square footage needed to be inside the allowable. We just spent 2 days in our office trying to figure out the tilt-up idea using the exact system you described. We finally decided that 4 sections, 20' wide and 15' (lowest eave) to 22' (peak) high, but eventually decided that walking around on the gyp while installing and taping might break some of it. Then, how to lift it without buckling the steel studs looked like an insurmountable problem. We had a 20' tall interior wall that was being framed up in a building that wasn't completely enclosed, wind got behind it and buckled the studs, folded the framing over. If a 20' section (or even 10' x 8 sections) bent or bowed the least little bit, I think the studs would buckle and we'd have a pile of useless gyp and steel. At a minimum, I'd expect some joints to pop if the wall bowed a little. Two layers of gyp on the 80' wall would amount to 6,600 lbs of gyp. Four sections would still be a lot of weight to pick up and move into position. Eight sections would still be 1,000 lbs each with steel included; that seemed too heavy to lift 8 sections perfectly without a failure. That would also assume a stretch of dry days during the process.

We thought there would be another problem linking the sections together since you couldn't tape the hidden backside seam. Spray firestopping between sections seemed the only option. We finally came down to a simple 6" block wall, with adequate reinforcing; wouldn't have to be pretty, just effective.

We measured the site all the accuracy of eyeballs and tape and think there may only be 29' to an interior property line. The owner has instructed his surveyor to provide a new site plan showing a relocated interior lot line that is 30' or greater from the building so we don't have a Table 602 problem. If the adjacent property ever sells to a separate individual, he'll have a bit less to mow.

 

[brudgers]

Uhh...I didn't describe a system.

 

[Builder Bob]

H channel shaft wall.

 

[DwightB]

Final score:

City: won

Architect: 0

The CBO pointed to 714.5 and said I'd have to fire-rate all of the structure (existing and new) to be IIIB, so I caved, will go with the firewall, choosing 8" block as the cost-effective solution.

While waiting on the city's response, research on the web shows that this issue has been in contention for years, even saw a comment by BuilderBob in '05 on iccsafe.

In the final outcome, Type VB, with the firewall, and qualifying perimeter increases on remaining 3 sides, both buildings are legal.

Client is not thrilled, but content with the solution.

 

[imhotep]

Final score:City: won

Architect: 0

The CBO pointed to 714.5 and said I'd have to fire-rate all of the structure (existing and new) to be IIIB, so I caved, will go with the firewall, choosing 8" block as the cost-effective solution.

While waiting on the city's response, research on the web shows that this issue has been in contention for years, even saw a comment by BuilderBob in '05 on iccsafe.

In the final outcome, Type VB, with the firewall, and qualifying perimeter increases on remaining 3 sides, both buildings are legal.

Client is not thrilled, but content with the solution.

Take a minute please and clarify the issue for me if you would.

As I understand the AHJ's interpretation it is that the exterior non-bearing metal cladding attached to girts does not constitute an exterior wall. That the structural frame the girts and cladding are hung off of is considered to be within the wall and so the frame must be protected as if it is a bearing wall - 2HR. Do I have that right? You do have > 30' separation on all sides, right? So I wonder what a non-bearing exterior wall is.

 

[DwightB]

imhotep: You got it right, This is the word from CBO:

Dwight, you have read the table correctly, however, as are many other things in the IBC code, some types of construction have requirements in other sections, this is one of those. Below is the section that refers to structural members in an exterior wall and the requirement that they have the same rating as the exterior bearing wall rating from the table, so to qualify a metal building as type IIIB construction the structure would need to be rated to 2 hours, which requires some sort of fireproofing or wrapping to meet this requirement. Based on these requirements, the existing buildings would not be classified as IIIB.

I do have 30' or more separation from the nearest interior property line, so no rating requirement because of that. Some people have told me that the skin actually does perform a structural function for the building, so that might be reason for it to be included in the definition of "bearing". But the section he quotes here specifically says that the columns must be included also.

I could envision a column and structural slab configuration with inset columns and aluminum storefront walls that would be very hard for any CBO to call "bearing", but I guess I lose on this one.

However, I still agree with you, the exterior structural columns (red iron frames) are hardly "within" the exterior wall and footnote "a", Table 601 specifically excludes structure, with no requirement pertaining to interior/exterior or "within" a wall.

Technically, At the beginning of all this, I did have an interior lot line about 5' away, however, the site has been surveyed and a new description is being written that will adjust the property line to 30' or greater from the wall.

xxxxxxx, CBO

Building and Neighborhood Improvement Supervisor

City of xxxxxx

(417) xxx-xxxx, Ext xxx

714.5 Exterior structural members. Load-bearing structural members located within the exterior walls or on the outside of a building or structure shall be provided with the highest

fire-resistance rating as determined in accordance with the following:

1. As required by Table 601 for the type of building element based on the type of construction of the building;

2. As required by Table 601 for exterior bearing walls based on the type of construction; and

3. As required by Table 602 for exterior walls based on the fire separation distance.

_Exterior load-bearing structural members, such as columns or girders, must have the same fire-resistance rating as is required for exterior load-bearing walls. As such, the required fire-resistance rating is the higher rating of that found in Table 601 for type of construction for structural elements or bearing walls or as required in Table 602 based upon the separation distance.

 

[DwightB]

Sorry to create confusion, the two paragraphs beginning with "I do have 30' ..." and ending with "...greater from the wall" are mine to clarify for imhotep, not from the CBO. All of the rest is the CBO's letter to me.

 

[DwightB]

Here's a clearer version:

imhotep: You got it right, This is the word from CBO:

Dwight, you have read the table correctly, however, as are many other things in the IBC code, some types of construction have requirements in other sections, this is one of those. Below is the section that refers to structural members in an exterior wall and the requirement that they have the same rating as the exterior bearing wall rating from the table, so to qualify a metal building as type IIIB construction the structure would need to be rated to 2 hours, which requires some sort of fireproofing or wrapping to meet this requirement. Based on these requirements, the existing buildings would not be classified as IIIB.

xxxxxxx, CBO

Building and Neighborhood Improvement Supervisor

City of xxxxxx

(417) xxx-xxxx, Ext xxx

714.5 Exterior structural members. Load-bearing structural members located within the exterior walls or on the outside of a building or structure shall be provided with the highest

fire-resistance rating as determined in accordance with the following:

1. As required by Table 601 for the type of building element based on the type of construction of the building;

2. As required by Table 601 for exterior bearing walls based on the type of construction; and

3. As required by Table 602 for exterior walls based on the fire separation distance.

_Exterior load-bearing structural members, such as columns or girders, must have the same fire-resistance rating as is required for exterior load-bearing walls. As such, the required fire-resistance rating is the higher rating of that found in Table 601 for type of construction for structural elements or bearing walls or as required in Table 602 based upon the separation distance.



I do have 30' or more separation from the nearest interior property line, so no rating requirement because of that. Some people have told me that the skin actually does perform a structural function for the building, so that might be reason for it to be included in the definition of "bearing". But the section he quotes here specifically says that the columns must be included also.

I could envision a column and structural slab configuration with inset columns and aluminum storefront walls that would be very hard for any CBO to call "bearing", but I guess I lose on this one.

However, I still agree with you, the exterior structural columns (red iron frames) are hardly "within" the exterior wall and footnote "a", Table 601 specifically excludes structure, with no requirement pertaining to interior/exterior or "within" a wall.

Technically, At the beginning of all this, I did have an interior lot line about 5' away, however, the site has been surveyed and a new description is being written that will adjust the property line to 30' or greater from the wall.

 

[imhotep]

imhotep: You got it right, This is the word from CBOwight, you have read the table correctly, however, as are many other things in the IBC code, some types of construction have requirements in other sections, this is one of those. Below is the section that refers to structural members in an exterior wall and the requirement that they have the same rating as the exterior bearing wall rating from the table, so to qualify a metal building as type IIIB construction the structure would need to be rated to 2 hours, which requires some sort of fireproofing or wrapping to meet this requirement. Based on these requirements, the existing buildings would not be classified as IIIB.

Thank you for the response. Had the same discussion with an AHJ and they determined that the frame was not within the non-combustible non-bearing exterior wall. Go figure.