What is a Mixed-Use Building?

MeyerFire University | LS101.03

By Chris Campbell, PE

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• Notes Page

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TRANSCRIPT

In the design and construction world, the terms “mixed use” and “mixed use building” are very common. 

Developers refer to new buildings that contain both office and retail spaces as mixed-use projects.  

Architects and Engineers refer to a floor containing multiple occupancy types as mixed-use floors.  

You’ll even hear AHJs use the term mixed-use when doing plan review from time to time. 

Colloquially, the “mixed-use” designation is meant to refer to a building or space that contains multiple occupancy types.  

But did you know that in the IBC, the International Building Code there are essentially no requirements pertaining to a mixed-use building?  

In fact, if you search for “mixed-use” in the IBC, you won’t find any requirements related to building height, building area, construction type, fire-rated construction or means of egress. 

Why is this? 

Long story short: there is a difference between “use” and “occupancy” in the IBC and people frequently confuse these two. 

The use of a space is a description of how that space will actually be used.  

This could be a broad, general description such as “office” or “conference room”, or it could be more specific, such as “visiting team locker room”. 

On the other hand, the occupancy classification of a space is 1 of 10 categories (plus subcategories) in Chapter 3 of the IBC. 

Occupancy classifications are limited to this list, but there are essentially an unlimited number of potential uses for a building or space.  

The use of a space is a factor in determining the occupancy classification, but the occupancy classification can only be one of the items listed here on the screen. 

So when people use the term “mixed-use,” it doesn’t mean much from a code standpoint, and practically, almost every buildings contain multiple uses.  

But what most folks intend to convey by the term mixed use is that the building has at least two distinct occupancy types, which the IBC would consider a “mixed occupancy” building.  

And unlike “mixed-use,” which does not have any requirements in the code, there are numerous requirements for “mixed occupancy buildings” in the IBC. 

The IBC offers three different ways to approach mixed occupancies: accessory, separated and non-separated, which we’ll get into more detail later. 

What is a mixed-use building? 

It is a building that contains multiple uses – which nearly every building does. 

What is a mixed-occupancy building? 

It is a building that contains multiple occupancy types. 

I’m Chris Campbell, this is MeyerFire University.