Duplex, adding 3rd apartment

[mtlogcabin]

The level of activity has changed as there are now three dwelling units instead of two.It sounds to me like you are saying that an "change in occupancy classification" means that a change within a group ("R" group) is not a change, , , I am saying that it IS a change in classification.

I said a change from a R-3 to a R-2 is not a change in occupancy classification. It is a change in occupancy and does trigger code requirements based in the IEBC or Chapter 34 of the IBC. It is quite clear looking at IBC 302.1 that there are 10 occupancy classifications and each classification have groups ranging from 1 to 5 assigned to each occupancy classification. Read Chapter 9 and think about it or better yet start diagraming the different sections where it talks about occupacy, groups and classification. They are different levels of requirements based on the level of change.

2006 IBC

302.1 General.

Structures or portions of structures shall be classified with respect to occupancy in one or more of the groups listed below. A room or space that is intended to be occupied at different times for different purposes shall comply with all of the requirements that are applicable to each of the purposes for which the room or space will be occupied. Structures with multiple occupancies or uses shall comply with Section 508. Where a structure is proposed for a purpose that is not specifically provided for in this code, such structure shall be classified in the group that the occupancy most nearly resembles, according to the fire safety and relative hazard involved.

1. Assembly (see Section 303): Groups A-1, A-2, A-3, A-4 and A-5

2. Business (see Section 304): Group B

3. Educational (see Section 305): Group E

4. Factory and Industrial (see Section 306): Groups F-1 and F-2

5. High Hazard (see Section 307): Groups H-1, H-2, H-3, H-4 and H-5

6. Institutional (see Section 308): Groups I-1, I-2, I-3 and I-4

7. Mercantile (see Section 309): Group M

8. Residential (see Section 310): Groups R-1, R-2, R-3 and R-4

9. Storage (see Section 311): Groups S-1 and S-2

10. Utility and Miscellaneous (see Section 312): Group U

Look at the intent of the IEBC it is not ment to be a "though shall do" the same for new construction document.

101.3 Intent.

The intent of this code is to provide flexibility to permit the use of alternative approaches to achieve compliance with minimum requirements to safeguard the public health, safety and welfare insofar as they are affected by the repair, alteration, change of occupancy, addition and relocation of existing buildings.

 

[Yankee]

I think there is a distinction being made here between "classifications" and "groups" that does not exist and is not intended. And, I don't believe there are necessarily any leniencies based on listings within a group. The flexibility is based on what was noted before, a "purpose or level of activity within a building". My justification being, a change within the R group from R3 single family to say an R1 motel is certainly a significant change in purpose or level of activity and so would need the highest level of fire protection required for an R1.

Whereas, an AHJ might easily consider a monitored fire alarm throughout the R3 to R2 to be sufficient given that the building is existing.

All that being said, I think we are saying the same thing.