Questions about New Construction between Existing Buildings

[ETThompson]

Hi

We're having some challenges on how to interpret the code relative to the following issues in a project I'm working on. See attached diagrammatic sketch. This is under the 2017 Ohio Building Code, based on the 2015 IBC.

We're added a glassy galleria space between two existing buildings (we are altering parts of the interiors of each, but not the exteriors in any significant way). We're planning on providing a 3-hr Fire Wall between this "connector" and the existing building to the south, mainly in order to avoid sprinkelering the southern building. We plan to add whatever we have to to the existing load-bearing masonry exterior wall of the south building in order to make it 3 hr, and provide fire shutters at any remaining openings. The "connector" plus the warehouse-type building to the north will be considered as one building for the purposes of the code, at least for now, and these will be fully sprinklered (they already have a system, may just need to be brought up to current code).

Conceptually we'd started with construction type IIIB (probably could change to higher level if we had to, but trying to see if it'd work as IIIB.). Therefore we'd be required to have 2-hr exterior rated walls (the rest of the elements in Table 601 are unrated).

Question 1: Can we consider the all glass curtainwalls at each end of our "connector" as openings in the exterior wall? Even if, as in the one to the west, it is set back from the rest of the warehouse building? If not, would we have to therefore rate these to 2 hrs? That doesn't seem feasible (we're on a very tight budget). Or are we forced to move to IIB (no exterior wall rating)?

Question 2: A Firewall needs to extend 18" beyond the "exterior face" of the wall (though there are some exceptions). For the connector, since the existing south building wall (which we're making 3 hr) extends well beyond the glass connector, does that then therefore mean we do not have to rate that for the 4'?

Question 3: Once we get 18" past the east wall of the connector, we no longer have to provide the 3 hr rating, correct?

Thanks in advance for any help you can give!

 

[RLGA]

Question 1: Yes, they can be considered openings (and probably would be). Only bearing walls of Type III construction are required to be of 2-hour construction. Nonbearing walls are subject to the fire-resistive requirements of Table 602 based on the fire separation distance. Openings will be limited in area, though, based on the fire separation distance per Table 705.8.

Question 2: At exterior walls, you have two options per Section 706.5.1:

1. Provide 1-hour wall construction and 3/4-hour opening protection for 4 feet in each direction. That would be 4 feet along the wall of the existing building (you have a 3-hour wall, so no problem there) and 4 feet into the glazed opening (that creates a problem for you); or,
2. Assume an imaginary lot line from the termination of the fire wall. The imaginary lot must be placed so that exterior walls and openings of both buildings comply with the fire separation requirements per Table 602 and Table 705.8, respectively.

Question 3: See response to Question 2.

One thing to keep in mind is that the new 3-hour fire wall must be structurally independent of the existing building and the connector--the roof system of the connector cannot be supported by the fire wall.

 

[ETThompson]

Thanks for the helpful responses! I hadn't noticed that the rating only applied to bearing walls. Much appreciated.

I can't quite picture the imaginary lot line, I will try sketching it out and possibly post it.

Yes, we know about not bearing on the existing / 3-hr wall, and are planning to avoid that. Thanks for checking though!

 

[RLGA]

Yes, we know about not bearing on the existing / 3-hr wall, and are planning to avoid that. Thanks for checking though!

If the 3-hour wall is the existing wall, then to consider that a fire wall the existing building also cannot use that as a load-bearing wall. If you are creating a double fire wall condition (back-to-back 3-hour fire walls) then any openings in those walls must have an opening protective that is independent of each wall (i.e., structural frame not attached to either wall), or you need to provide two opening protectives--one on each side of the opening.

 

[ETThompson]

Uh-oh, that is a potential problem. I'm sure the existing building does use that as a load-bearing wall. So, to address that, we'd have to build a structurally independent 3 -hr fire wall outside of the existing masonry wall? (I'm assuming it could not go inside the existing building). Why would it need to be a double wall (or would it)? I'm not sure we can assume the existing masonry wall is 3-hr - the research I did indicated probably 1 hour for existing load-bearing masonry walls.

Is there no provision or exception for an existing condition?

Thanks

 

[ETThompson]

A little troubling since this design was developed by a previous team in 2016 and even given a preliminary review w the building dept. Either they missed that or they had some way of solving!

 

[ETThompson]

If this is the requirement:

706.2 Structural stability. Fire walls shall be designed and constructed to allow collapse of the structure on either side without collapse of the wall under fire conditions. Double fire walls shall be supported laterally by the building frame on its respective side and shall be independent of the fire wall and framing on the opposite side, except for the foundation and flashing.Cantilevered fire walls or tied firewalls designed and constructed in accordance with NFPA 221 shall also be deemed to comply with this section.

Then does that not mean we could make sure the new 3-hr wall (existing masonry load-bearing plus whatever we have to add to make it 3 hrs) could be braced so that it stands while the existing south building falls? In other words, can't the existing building continue to use that as a load-bearing wall as long as if and when it collapses under fire conditions, the fire walls stays?

 

[RLGA]

If this is the requirement:

706.2 Structural stability. Fire walls shall be designed and constructed to allow collapse of the structure on either side without collapse of the wall under fire conditions. Double fire walls shall be supported laterally by the building frame on its respective side and shall be independent of the fire wall and framing on the opposite side, except for the foundation and flashing.Cantilevered fire walls or tied firewalls designed and constructed in accordance with NFPA 221 shall also be deemed to comply with this section.

Then does that not mean we could make sure the new 3-hr wall (existing masonry load-bearing plus whatever we have to add to make it 3 hrs) could be braced so that it stands while the existing south building falls? In other words, can't the existing building continue to use that as a load-bearing wall as long as if and when it collapses under fire conditions, the fire walls stays?

As you said, you would have to build a new 3-hour fire wall that is structurally independent of either building and, therefore, you could leave the existing wall as-is. Openings through both the existing exterior wall and the new fire wall are acceptable, but the opening protective will need to be installed in the opening located within the fire wall.

 

[ETThompson]

I understand that what you describe (totally independent fire wall) is an option, but could we not supplement the existing masonry wall (to make it 3 hrs and brace it so it stands if the existing falls down)? In other words, as long as this existing + new wall doesn't come down in a fire, doesn't that meet the requirement? Of course it may or may not be feasible to do this, but if we can is there a reason in the code that that cannot work?

 

[steveray]

Use the 2018 IBC, draw a lot line and do nothing between the 2 buildings if you get some easements?

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. 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 code official’s review
and approval, he or she 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.

Oh...wait we discussed that and it might not let you out of sprinklering unless it meets H&A....But maybe it does?

 

[ETThompson]

Thanks for the suggestion, but I don't think it passes that way. It's a little hard to tell with the existing condition, we'd need to know more. But the main thing is as overall B occupancy with no sprinklers we're limited to 19,000sf, and this existing southern building is 34,100sf. We'd basically have to be Type I construction to pass as non-sprinkelered.

The existing building is a load-bearing exterior masonry structure with wood roof framing (including large trusses over the dance studios). The previous team notes IIIB construction, which we'd have to confirm. I'm not quite sure how to do this with an existing structure, although there is info in the appendix.

The other issue is the costume storage area (which we're assuming is S-1). It appears to be less than 10% of the area of the overall, so maybe is an accessory use (about 2,500sf out of 34,100 total for the southern existing building). This costume storage area also might be sprinkelered, the 1990 renovation drawings note it as "limited area sprinkeler" but I don't see any in my pics, will have to check next time I'm there.

But regardless, it doesn't seem to pass. :-(

 

[ETThompson]

If the 3-hour wall is the existing wall, then to consider that a fire wall the existing building also cannot use that as a load-bearing wall..

I'm still not quite sure I understand why this is necessarily the case. Is it not theoretically possible to brace and add to the existing masonry wall in order to make it a 3-hour Fire Wall? If the existing roof structure bearing on this wall burns and falls away, and we can demonstrate that the Fire Wall will still stand after that, doesn't that meet the requirement? I do understand that it may not be practical, but isn't this - in theory - possible?

 

[Builder Bob]

Pedestrian Walkway See Chapter 31 of the building code - Section 3104

 

[ETThompson]

Pedestrian Walkway See Chapter 31 of the building code - Section 3104

I appreciate the thought, but this Connector is more than a pedestrian walkway. It will function as not only the primary (2) entries to the building (from street and from parking lot, on opposite sides), but also a circulation hub serving many of the functional spaces, and is also conceived of as a multifunction space which can house large fundraising meetings, gatherings and special events. It is currently about 35' wide and about 90' long, so I think we'd be stretching things to consider it a pedestrian walkway, but I appreciate the idea (and I didn't know about that section, will keep in mind for future use).

 

[Tim Mailloux]

what is the occupancy of this building? This sounds like an A-3 occupancy to me which is required to have sprinklers if it has a fire area exceeding 12,000SF.

 

[ETThompson]

Yes the "Connector" piece is probably A-3, that's what we've been assuming, and we're assuming it is sprinkelered. But we don't want to sprinkler the adjacent existing building.

I'm now looking into our Chapter 34...I understand the IBC has moved to the IEBC but we still have the old Chapter 34 here in Ohio. I'm seeing some promising things in here...

3403.1.2 Additions to buildings of Groups other than R and I occupancies.When the combined height and area of the existing building and the addition exceeds the height or area allowed by Chapter 5 including any area increases permitted, the following shall be permitted:

1. A fire wall that complies with Section 706 shall be constructed between the existing building and the addition. When a fire wall is constructed to separate the existing building from the addition, the addition shall be considered a separate building.

2. A fire barrier that complies with Section 707 as required for separating fire areas shall be provided between the addition and the existing building. When a fire barrier is constructed to separate the existing building from the addition, all the following shall apply.

a. The combined height and area of the addition and existing building shall be used to determine the construction type and fire protection requirements for the addition.

b. The construction type of the existing building and the addition may differ.

c. Fire protection system is not required in the existing building when a fire protection system is required in the addition.

 

[Tim Mailloux]

Which building (north or south) are the dance studios located in?

 

[ETThompson]

Both. The south, older, non-sprinkelered building has roughly half a dozen. We are doing only very minimal alterations in this building (adding a corridor between two dance studios, adding a small kitchenette, cosmetic and mechanical upgrades). The north building is currently a black box theater and storage / set building spaces, we are adding one dance studio in this north building. It is sprinkelered though not sure it is up to current code. That said, we'd always planned to upgrade the north building, although if we didn't have to...

 

[Tim Mailloux]

With all those dance studios in the south building, why is it classified as a B occupancy? Im pretty sure I have seen several interpretations from the ICC that dance studios fall under A-3, not a B occupancy.

 

[ETThompson]

That came from the section in B that states "Training and skill development not in a school or academic program (this shall include, but not be limited to, tutoring centers, martial arts studios, gymnastics and similar uses regardless of the ages served, and where not classified as a Group A occupancy)."

This was actually suggested by the Bldg. Dept as an option to the the earlier (2015) design team, they did say that the studios would have to be noted as 49 occupants or fewer, which should be fine.