There is a maze of requirements for existing buildings between the 2012 IBC Chapter 34, 2012 IEBC, and ASCE 41-13. Depending on the project type and whether or not the project is voluntary or triggered, different requirements apply.

Here is a question we recently received after David Bonowitz’s ASCE 41-13 Overview web seminar and his response.

Please note that the following terms are defined in Chapter 2 of the 2012 IBC:

ADDITION. An extension or increase in floor area or height of a building or structure.

ALTERATION. Any construction or renovation to an existing structure other than repair or addition.

Q: After using ASCE 41-13 to perform a seismic assessment on a building, our client has decided to retrofit the building by adding a new seismic-force resisting system (SFRS) to the exterior of the building. What code should I apply for this added SFRS? Should I use ASCE 7, AISC 341, and so on, or ASCE 41-13?

2012 IBC Section 3403.1 requires new additions to comply with codes for new construction. If we accept this provision, the analysis will be run at least 3 times; BSE-1E, BSE-2E, and ASCE 7-10 seismic forces. What is your opinion on this?

A:  If I understand your question, 2012 IBC Section 3403 (Additions) does not actually apply because this is a retrofit of an existing building, not an addition. As long as the intended project is not adding square footage to the building, it’s not an addition project. New elements or components that are “added” do not make it an addition. Rather, in code terms, if you are only doing the seismic work you described, this would be an Alteration project with a voluntary seismic retrofit.

So since it’s voluntary, you can use ASCE 41-13 by itself as criteria, and the code section that applies is 2012 IBC Section 3404 (Alterations), including the allowance in Section 3404.5. As for the performance objective, you are free to use any objective that your client wants.

On the other hand, if it’s a triggered retrofit — for example, you’re doing the retrofit because a change of occupancy demands it — then the performance objective is set by the code, but you can still use ASCE 41 by itself. If you’re in the IBC, you do that with IBC Section 3401.6, which allows you to use the IEBC, and then you use the ASCE 41 option in IEBC Chapter 3.

This is a good example of how the context of the work — voluntary or triggered, and if triggered, what project type — makes a difference.