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IBC Chapter 34 Section 3407.1

IBC Chapter 34 Section 3407.1

IBC Chapter 34 Section 3407.1

(OP)
I have a project that I am going to look at this morning with a client. The project is a current two story building that is approximately 45’ tall with a second floor at 14 feet built around 1900. The client would like to turn the building into an apartment building. The client would like to add another story inside of the 30’ tall space. I have yet to make a site visit (this morning) but I am assuming the building has multiwythe brick walls around the perimeter. From what I have been told, the building is on the National Historic Register (which is amazing as it doesn’t appear to have any historic value from what I have seen/location).

There is an architect and GC that are already working on the project. The architect and GC have had discussions with the building inspector in regards to the project. I am being told that the building inspector is willing to waive any seismic upgrades needed on the building. I’m not sure what exact provision of the code the building inspector is using, but I am thinking it is section 3407.1 (hopefully I will find out today but I probably will not).

My question is, how would others feel about this exemption being given in writing from the building inspector? I am having mixed feeling about it.

RE: IBC Chapter 34 Section 3407.1

3407.1 seems like a nice blanket provision giving the building official room to allow older buildings (historic) to not be altered to an extent that would perhaps destroy the historic aspect of the structure.
(per IBC 2006 - note that the numbering appears different in the IBC 2012).

However, adding a full floor is pretty extreme. What if the owner wanted to add 6 stories to the top of the building?

I think as EOR, you still have the responsibility to look out for the public safety and welfare.
If the added floor, in your view as an engineer, would be too much in terms of seismic safety, I think you have a decision to make regarding your continued participation in the project.

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RE: IBC Chapter 34 Section 3407.1

agreed it sounds sketchy...I'd want to know if the inspector is speaking on behalf of the municipality which may have some interest in seeing an abandoned site rehabilitated, or is he just speaking on behalf of himself giving his opinion. He may move on next year but that building will be there a long time.

RE: IBC Chapter 34 Section 3407.1

(OP)
Triangled,

I would say that there is a push to upgrade this section of the city which has seen quite a bit of neglect for the past 30+ years. This particular project used to have a theater on the second floor hence the high ceilings. I made a site visit yesterday and there has already been a partial third floor added which covered 3/4 of the area in question.

I am definitely a bit worried about the project. I need to get a proposal to the client, but may give them a proposal with the caveat that some additional shear walls need to be added in certain areas. This will either give me the boot or let me get a few additional walls in some areas.

And JEK is correct, I believe the section is 3409.1, but I am dealing with the IEBC which many do not have experience with so I grabbed the first IBC I could find to locate the same paragraph within.

RE: IBC Chapter 34 Section 3407.1

I just had a chapter 34 question a few days ago - it's a trend.

This probably varies with your area/market in terms of how comfortable you are with this concept. In my area it is very common to add a story, it is not uncommon to add several, so I don't think this is necessarily sketchy based on concept alone. If the building is junk or you can't provide a rational analysis then it's sketchy - otherwise it may be a good reuse of an existing building that would otherwise get demolished.

RE: IBC Chapter 34 Section 3407.1

Can you can structurally separate the new floor addition from the existing structure and provide it's own lateral and gravity system?

RE: IBC Chapter 34 Section 3407.1

(OP)
bookowski,

They not even adding a floor to the outside of the building, I'm adding a floor to the inside of the building (ie not really a change in the wind loads).

I was going to hijack your thread but decided not to, and your thread is the reason why I posted. Usually Chapter 34 questions go unanswered especially any that deal with the IEBC. I'm glad that we are starting to receive and answer some questions from this section of the code.

DETstru,

The new floor is inside the existing building. They are expecting to support for the gravity system using the existing foundations and columns which run at a 15'x15' grid, so framing this new floor independent of the existing is not going to be possible.

RE: IBC Chapter 34 Section 3407.1

Since you are having to make a judgment call, I would consider other factors, too:

1. What is the relative seismic risk for this site, compared to all geographic areas addressed by IBC? Since IBC gives building officials authority to waive certain code provisions for historic buildings, would it be reasonable to assume this building is located in what IBC considers a low-risk seismic area?

2. If there have been any seismic events since the existing building's construction (c. 1900), how did the building perform?

www.SlideRuleEra.net idea
www.VacuumTubeEra.net r2d2

RE: IBC Chapter 34 Section 3407.1

How can a building inspector authorize changes to an Historic Building? I do not see that he has the authority. Seems to me any proposed changes, structural or otherwise, should be run past the Historical Society to avoid pissing off the wrong people.

Also, if this is unreinforced masonry construction, has it been seismic ally retrofitted in the recent past?

Mike McCann, PE, SE (WA)


RE: IBC Chapter 34 Section 3407.1

(OP)
SlideRuleEra,

I'm not sure what relative seismic risk to the site is, I have only practiced in the area so I'm not familiar with how bad things may be. I can tell you that Ss=0.24 and S1=0.067. Most structures in the area end up in a SDC C.

Msquared,

Again, I think the city would like this building updated since it has been neglected for so long. The city recognizes this and the trouble with updating buildings with mulitwythe bearing walls for seismic codes and here we are. I am thinking this is not the first project the city has run into as from what I am told, they offered up the out even before the architect could ask the BI.

RE: IBC Chapter 34 Section 3407.1

I have no where near the experience of some of the above, (nodding to you bookowski), in this kind of scenario, so with that being said, a couple of thoughts:

slideruleera touches upon exactly my default consideration, being a California reared engineer. Your Ss seems to indicate relatively small seismicity, at least to me in California...likely wind would govern your design of a new building in your building's area, and, like said above, your building face isn't changing size. But as you know seismic forces are directly related to mass and URM has a lot of mass and has been a major challenge out West. Wind and seismic codes evolved relatively slowly in the 20th century and perhaps your building hasn't been designed with any lateral loads in mind.....do you have any idea of the age of the structure?

The theater occupancy you mentioned answers my unspoken question about the 30' high ceiling for the 2nd floor. It also suggests that, perhaps, your second floor, and the 1st to 2nd floor walls were designed to handle a larger live load (maybe?) then your proposed occupancy I'm guessing), so you might have some reserve strength there. Perhaps your new 3rd floor would have a lateral system (DETstru) that transfers down to the 2nd floor level, at which you might (maybe) have some reserve capacity?

Msquared is speaking to my point regarding the building inspector's willingness to issue a letter of some sort. The municipality will receive taxes, the politicians supporting redevelopment will receive applause, the owner will receive revenue, and you will receive your fee. But you seem to be carrying an outsized liability. I would think the municipality would share or even assume the entire liability, although I can't say I've ever heard of such a thing (but could be entirely my inexperience in this kind of scenario), but it seems reasonable to me....which covers you financially.

Then all that remains is the ethic that JAE perfectly stated.

RE: IBC Chapter 34 Section 3407.1

SteelPE - I'm proposing to take a look at the seismic maps (i.e. Figure 22-1 and 22-2 of ASCE 7-10) or even a website such as USGS Earthquake Hazard Program. The spectral response accelerations for this project are modest compared to high-risk areas such as the Western States, Missouri-Arkansas, and South Carolina. The Seismic Design Category is "Moderate".

Then make a complete walk-thru visual inspection of the existing building, 115 years, or so, is plenty of time for poor design, workmanship, or materials to show evidence of problems... if you look for them.

With the above information, you can make an informed opinion on how wise it is for the building inspector (acting in his official capacity, as Triangled noted) to waive certain code requirements. In this case, if the building looks sound then waving the requirements, while not conservative, is probably reasonable.

Note that all of the above is only to evaluate one factor, the inspector's judgment. The wisdom of the proposed work still has to be considered. Make the most of all information available to you.

www.SlideRuleEra.net idea
www.VacuumTubeEra.net r2d2

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