Usually, the building codes mandate a maximum square footage for a building based on its occupancy and construction type (fire resistance of materials). But, there are certain provisions for buildings that have no limit to the allowable area, given certain requirements are met. Here we will discuss an overview of how the IBC permits unlimited area buildings and the regulations surrounding them.
Nonsprinklered Buildings (One story)
An nonsprinklered building can be unlimited area and 1 story if it meets the following:
-F-2 or S-2 occupancy
-A 60 ft yard (space between the building and the property line or adjacent buildings)
Sprinklered Buildings (One Story)
Sprinklered buildings can be unlimited area and 1 story if it meets the following:
-B, F, M, or S occupancy
-A-4 occupancy (must be of other construction than type V)
-A 60 ft yard (space between the building and the property line or adjacent buildings)
Sprinklered Buildings (Two Story)
Sprinklered buildings can be unlimited area and 2 stories if it meets the following:
– B, F, M, or S Occupancy
-A 60 ft yard (space between the building and the property line or adjacent buildings)
H-3 Occupancies within Unlimited Area Buildings
H-3 (High Hazard) occupancy is allowed to make up 10% maximum of the building but no more than its normal allowable area from table 506. For example, if the building is 80,000 sf, 8,000 sf of it can be H-3. If the building is type II-B (all metal structure), then this would work.
Additionally, the code has limitations on the location of H-3 within the building. Preferably, the occupancy has at least 25% of its perimeter on an exterior wall, in which case you can generally have the full 10% area. If the H-3 must be interior to the building, then the code (507.8.1.1) mandates it can be no more than 25% of its normal allowable area. Flammable liquid storage rooms can be up to 1,000 sf and be interior to the building as well (507.8.1.1.2)
Summary
Unlimited area building rules come into play when buildings need to be very large area. They are not tall, but are large. These are often on very large sites with plenty of room to have space surrounding the building.
These are just some of the main types/ requirements regarding unlimited area buildings. Please refer to the code for more information, section 507 of the 2021 IBC.
Article By: Matthew Taylor-Rennert, Architect
