Existing Structure - Re-model - When to meet updated Codes

[CBSE]

I recently received a project that involves a local grade school. The work involves:

1) Taking out and installing new windows
2) Adding (2) additional classrooms
3) Miscellaneous repair and replace items

The school has basically no lateral restraint system as it currently stands...literally, the walls are 98% windows with about a 12" return corner.

The Architect and School District are asking if we need to do seismic upgrades to the building since we are replacing windows and adding classrooms. I planned on designing the class rooms as stand alone systems and not touch the existing building. How far would I need to go if I did upgrades to the worst parts of the lateral system? There's at least one wing that has shear walls on (3) sides. The wings are long...probably 140-180ft long and about 30-40ft wide.

Would I need to do upgrades at all because we aren't changing any loads on the system as a whole? The building is wood framed with brick veneer.

 

[SteelPE]

What building code are you using?

 

[CBSE]

I'm not sure. I would think the existing building code.

 

[CBSE]

I guess I'm not sure how to approach it from a building code standpoint. I'm not adding any additional load to the current lateral system. But any upgrades to the current system would be an improvement.

 

[Archie264]

Speaking from memory, I thought the criteria of the IBC was that if you increase the load on a building or any of it's components by 10% or more it had to be upgraded to meet current codes. But note that what has to be upgraded is that which is getting the increased load. In other words, if it's simply a component that is receiving the increased load that is what must be upgraded, not necessarily the whole building. That's how I remember it, at least.

My take on my understanding of the situation you describe is that you don't have to upgrade the building's lateral system but if you do you have to address the whole thing. Which is quite a shame, since, as you noted, any upgrade would be an improvement. Perhaps you could get the school administrators to ask the building officials for a waiver thus allowing you to partially improve it as funds allow? If that doesn't work bring it before the Parent-Teacher Association and they might be willing to apply political pressure as needed.

Take all of the above with a grain of salt.

 

[manstrom]

Archie is right about the 10% rule.

Be careful where you tread regarding the seismic retrofit idea. The original concept *may* have been designed to code. Maybe they used some tricks to make the open diaphragm work. Read up on the Existing Structures part of the code. Your small reno could turn into a huge cost if you do need to do the seismic repair and that may ruffle some feathers (or condemn the school). On the other hand, no one wants a school falling down in an earthquake.

To keep your butt covered, you should probably request a fee to do a structural observation for the lateral system and dig deeper. If you could get drawings, that would help a lot.



When I am working on a problem, I never think about beauty but when I have finished, if the solution is not beautiful, I know it is wrong.

-R. Buckminster Fuller

 

[CBSE]

Thanks guys. There are existing drawings and I'm supposed to get access to them today. My gut is telling me they may originally relied on gyp-board fir interior shear walls. the diaphragm L/W ratio is like 8:1 if they assumed no interior shear walls.

I like the idea of talking with the building department.

 

[Ron]

There is also a cost/replacement percentage requirement for upgrade. As an example, if you replace more than a certain percent of the roof, the current code applies. If your remediaton cost exceed a certain percent of the replacement cost of the building, current codes might be interjected.

 

[CBSE]

They are not doing anything with the roof. As near as I can tell, per the existing building code, I can do "voluntary" upgrades to the system in an effort to improve what is there. Since the remodel is not affecting any of the structural elements, it appears there is no need to do any updates, aside from the "voluntary" updates if requested.

 

[SteelPE]

So, most of the responses above are assuming that you are using the IBC. Is this correct? It shouldn't be that hard of a question.

If you are using the IBC you will be in chapter 34. There are a few structural paragraphs in chapter 34 that relate to your problem. Some jurisdictions eliminate chapter 34 in favor of the IEBC.

I have heard of the cost requirements described by Ron, but I don't think I have ever seen them in either of these two codes (although I have seen work area referenced).

If you are in the IEBC, one more thing to note is that I believe both you and the architect need to be on the same page with your design approach. If the architect is the prescriptive compliance method or the work area compliance method you need to be using the same (unless the building official says otherwise).

I think you will find that if your new addition is structural separated from the existing school and you are not modifying any structural items in the school an upgrade may not be required.

 

[Jc67roch]

I have seen this ALOT, and I agree with the previous posts. You need to review the extent of work against the project classifications in IBC Chapter 34 or the IEBC, whichever is applicable in your state. The project classifications (repair, alteration, ADDITION require differing levels of compliance or upgrading with respect to the current code requirements - particularly for lateral systems. As has been noted, in my experience, often the most practical approach is to design the additions to be structurally independent - probably with just an expansion joint or connecting corridor to the existing building. But depending on the level, extent, and cost of the work within the existing building areas, you may still be required to check the lateral systems, and then reinforce them to meet current code.

 

[CBSE]

The only place I can find the cost of rehabilitation is in the historic and accessibility sections, and there isn't anything in there about requiring lateral upgrades. I'm under the Oregon Structural Specialty Code.

I can't find anything that says that lateral upgrades are required for replacing windows. Maybe I'm missing something?

As far as the classification, there aren't any repairs/alterations/additions to any of the structural elements of the building. I will design the (2) new classrooms as stand-alone systems. That being said, the only part that I see as applicable is the "Voluntary Seismic Upgrades" section.