Mezzanine Structure Fire Rating

The fire-resistance rating of a mezzanine structure often comes into question during design. Common questions asked include: What materials are permitted to be used? What is the required fire rating of the structure? What penetrations of the mezzanine floor need to be protected?

As no specific direction is provided in the mezzanine section of the building code (IBC Section 505), the construction of mezzanines is required to conform to the following:

  • Constructed of materials consistent with the construction type of the building. If the building is composed of Type I or II construction, the mezzanine structure must be noncombustible.
  • Structure (columns, floors, beams, etc.) is required to be fire-rated consistent with the construction of the building in accordance with Section 601; and
  • The fire rating of mezzanine floors is not required from a vertical opening perspective, only a structural stability perspective.  As such, penetrations of the mezzanine floor are not required to be protected with approved firestop assemblies provided the omission of such assemblies does not compromise the structural integrity of the floor in a fire event.

For example, if a building is Type IIA Construction (non-combustible, 1-hour frame), a mezzanine is required to be constructed of non-combustible materials with a 1-hour fire rating.  Penetrations of the mezzanine floor (i.e. pipe penetration) are not required to be protected with a firestop assembly provided this will not impact the integrity of the mezzanine structure during a fire.