A mezzanine is a common design feature found in all types of buildings. Some common ones are warehouses, factories, assembly halls, etc… The building code outlines some basic rules for mezzanines to help determine if it is an intermediate level within the room it serves or if it is considered another story. More on what a “story” is in another post, since this is worthy of its own post.
First of all let’s start off with the definition. A mezzanine is an intermediate level between the floor and ceiling of any story. In regards to the building code, mezzanines must comply in accordance with Section 505.2 of the IBC.
Mezzanine Area and Story
A mezzanine in compliance with Section 505.2 shall be considered a portion of the story it serves below. Such mezzanines do not need to contribute to either the building area or number of stories as regulated by Section 503.1, when determining how big or tall a building can be. However, even though it is not factored into the building area, its square footage shall be included when determining the fire area.
Mezzanines can be great features within a building because they provide an additional floor level without being considered an additional story as long as they comply with Section 505.2, which we will get into. Now even though they don’t contribute to the “building area” or number of “stories” regulated by Section 503.1, they must still be included within the “fire area” calculation when determining the need for fire protection systems.
Another important piece of information is that they should be constructed of consistent materials according to the building’s construction type per Table 601. More on the topic of “construction types” at a later time since this topic is so important, it deserves its own post!
505.2.1 Area Limitation (Limited Area)
The clear height above and below a mezzanine shall not be less than 7 feet.
The total area of a mezzanine within a room shall be not greater than 1/3 the floor area of the room in which it is located.
Without going into detail, there are some exceptions in the code that allows for the mezzanine to be larger given certain factors such as the buildings type of construction and whether the building is equipped with an automatic sprinkler system and emergency communication system.
505.2.2 Means of Egress (Exiting)
The means of egress for mezzanines shall comply with the applicable provisions of Chapter 10.
A mezzanine acts like a room or space in which it has an occupant load and that occupant load must have the correct existing parameters per Chapter 10 (egress chapter). I will leave this here for now since the topic of “Egress” is a whole other animal. In terms of mezzanines, the code does not have any additional exiting requirements other than the typical requirements found in Chapter 10.
A mezzanine shall be open to the room in which it is located, except for walls not more than 42 inches in height.
The code does however provide some exceptions related to the “openness” of the mezzanine provided certain conditions. If you meet these exceptions, the mezzanine would not be required to be open. Without getting into detail, one exception would be if the occupant load of the mezzanine is not more than 10 and another is if it has at least two exits out of the space. In this case you could have an enclosed mezzanine space.
Summary of Mezzanine Code Requirements
– A mezzanine is an intermediate level between the floor and ceiling of any story.
– The clear height above and below a mezzanine shall not be less than 7 feet.
– The total area of a mezzanine within a room shall be not greater than 1/3 the floor area of the room in which it is located.
– The means of egress for mezzanines shall comply with the applicable provisions of Chapter 10.
– A mezzanine shall be open to the room in which it is located or enclosed depending on the occupant load or number of exits serving the mezzanine space as noted above.
– A mezzanine in compliance with Section 505.2 shall be considered a portion of the story it serves below and does not need to contribute to either the maximum allowable building area or number of stories as regulated by Section 503.1, however its square footage shall be included when determining the fire area.
* Reference Source – 2015 International Building Code – [Buy on Amazon]