What am I today?

[rktect 1]

So I have an existing type 3A building designed for M use fully sprinklered. The building was built in 1975 BOCA. It has non combustible walls with 2 hour ratings and a timber arched roof that starts at about 15 feet above the floor and spans to a height of about 30 feet. Roughly 48,000 sq. ft. All columns are protected with 1 hour rating. Today, they want to modify this building and turn it into an A-3 use.

What construction type am I in 2018 IBC

 

[classicT]

Have you approached this from the perspective of the IEBC? You would be moving up from a relative hazard category 3 to a level 2; therefore IEBC 1212.5.1 applies.

1012.5 Heights and Areas
Hazard categories in regard to height and area shall be in accordance with Table 1012.5.

TABLE 1012.5 HEIGHTS AND AREAS HAZARD CATEGORIES

RELATIVE HAZARD OCCUPANCY CLASSIFICATIONS
1 (Highest Hazard) H
2 A-1, A-2, A-3, A-4, I, R-1, R-2, R-4
3 E, F-1, S-1, M
4 (Lowest Hazard) B, F-2, S-2, A-5, R-3, U


1012.5.1 Height and Area for Change to Higher Hazard Category
When a change of occupancy classification is made to a higher hazard category as shown in Table 1012.5, heights and areas of buildings and structures shall comply with the requirements of Chapter 5 of the International Building Code for the new occupancy classification.

Exception: For high-rise buildings constructed in compliance with a previously issued permit, the type of construction reduction specified in Section 403.2.1 of the International Building Code is permitted. This shall include the reduction for columns. The high-rise building is required to be equipped throughout with an automatic sprinkler system in accordance with Section 903.3.1.1 of the International Building Code.

1012.5.1.1 Fire Wall Alternative
In other than Groups H, F-1 and S-1, fire barriers and horizontal assemblies constructed in accordance with Sections 707 and 711, respectively, of the International Building Code shall be permitted to be used in lieu of fire walls to subdivide the building into separate buildings for the purpose of complying with the area limitations required for the new occupancy where all of the following conditions are met:

1. The buildings are protected throughout with an automatic sprinkler system in accordance with Section 903.3.1.1 of the International Fire Code.
2. The maximum allowable area between fire barriers, horizontal assemblies, or any combination thereof shall not exceed the maximum allowable area determined in accordance with Chapter 5 of the International Building Code without an increase allowed for an automatic sprinkler system in accordance with Section 506 of the International Building Code.
3. The fire-resistance rating of the fire barriers and horizontal assemblies shall be not less than that specified for fire walls in Table 706.4 of the International Building Code.

Exception: Where horizontal assemblies are used to limit the maximum allowable area, the required fire-resistance rating of the horizontal assemblies shall be permitted to be reduced by 1 hour provided the height and number of stories increases allowed for an automatic sprinkler system by Section 504 of the International Building Code are not used for the buildings.​

 

[mtlogcabin]

2018 IBC one story A-3 use IIIA full NFPA 13 system is permitted to be 56,000 sq ft with a maximum eight of 85 feet

 

[mtlogcabin]

You are still a 3-A type building

 

[rktect 1]

I think what threw me is that in the 1975 BOCA code it has the table list as 3A Heavy Timber, 3B protected and 3C unprotected. I had to wonder if this 3A Heavy Timber went to type 4 in the 2018 IBC