Is it a Mezzanine?

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Is it a Mezzanine?

Postby Blackstone on Thu Nov 20, 2008 10:29 pm

When is an 'alleged mezzanine' not a true mezzanine?

Most Code Analysis begins with the presupposition that the area in questioned was a Mezzanine, and continues to outline the various 2006 IBC Mezzanine requirements. The presupposition assumes that the upper level met the definition of a Mezzanine, and assumes it is located in the adjacent room as opposed to being located in the rooms directly below it where the successive levels occur. The contention is whether the area met the definition of a Mezzanine (which seems is never addressed in most Code Analysis), and thus could use the 2006 IBC / 2000 LSC Mezzanine requirements which are less restrictive than that for a ‘Story’ - the default definition if an area with successive floor levels fails to meet the definition of a mezzanine, penthouse, basement, etc.

First, the upper level needs to meet the ‘definition’ of a Mezzanine, not whether ‘as a Mezzanine’ it met all Code requirements. The 2006 International Building Code (IBC) defines a mezzanine as being "an intermediate level or levels between the floor and ceiling of any story with the aggregate floor area of not more than one-third of the room or space in which the level or levels are located" – this does not appear to mean “not more than 1/3 of the story in which it is located”! (Penthouse is not more than 2/3 of the roof area of the story below, and in 2000 LSC, Section, existing Mercantile still provides ‘not more than ½ of the story’) A mezzanine is considered to be a second story and is subject to the Building Code requirements for a second story if:

It covers more than 33 1/3 % (66 2/3 % for Construction Type I & II Industrial Occupancies) of the horizontal plane separating the mezzanine from the floor space that it occupies (i.e. where the successive floor levels occur), or; It is not visually open to the floor space of the room it occupies (room below which is the most direct fire/smoke threat) unless it meets the exceptions of 2006 IBC, Section 505.4 (also, how could an enclosed space on an alleged ‘Mezzanine’ [permitted by the exceptions to be partially or even fully enclosed!] also be considered a part of an adjacent room?).

Mezzanine levels with enclosed spaces below them can not exceed 1/3 of the floor space of any of the room enclosures below where the level is located – that is, also in which any portion (aggregate) of the Mezzanine floor is located. Example - A ‘balcony’ that is half over a sanctuary and half over the narthex (lobby), and each half of the ‘balcony’ is less than 1/3 of the room it is over (occupies), complies with the definition restricting the area of a Mezzanine. The example could even have enclosed spaces on it meeting the 2000 IBC, Section 505.4 exceptions, and still be a Mezzanine since these enclosed spaces would aggregately never exceed 1/3 of the floor space below.

Note the difference in the 2006 IBC from that of the previous SBCCI definition which addressed enclosed spaces under a Mezzanine as not being included in determining the size of the room or space in which the Mezzanine is located. In the IBC definition, the spaces under the Mezzanine provision is conspicuously absent, as is the SBCCI section (also missing) which permitted open stairs from Mezzanines where the space below is enclosed but provided with smoke detection. The point is that the definition of a Mezzanine has evolved over the years to its present state, presumably in an attempt to return to the spirit of the original intent of a Mezzanine which seems to have been abused, and to more clearly limit the use of the special privileges entitled to a Mezzanine: A flooring laid over a floor to bring it up to some height or level (mezzanino – Italian) ~ typically to raise the function of that lower area ‘out of the way’ to allow the lower floor to be more ‘open’ for functionality.

Mezzanines are considered a portion of the floor below. The 2000 LSC Handbook Table 36/37.1 indicates ‘….1/3 the area of the floor below…’ alluding that the room or space in which the level or levels are located is the floor space of the room below, and not abstractly construed as the floor space of some room somewhere adjacent to it that happens to have a floor level lower that the upper level ~ especially enclosed portions of the aggregate that do not even share an atmosphere with the adjacent space (sometimes used to legitimize transposing the upper level’s ‘location’ to the adjacent space). The usable space below the Mezzanine is placed on top of the Mezzanine, and the space below is left open for occupant traffic, architectural openness, etc. – essentially transposing the portion of the floor below to the Mezzanine to achieve dual functionality. Using both levels as a usable space (e.g. enclosed rooms above and below) is more of a function of two stories - not that intended of a Mezzanine.

Finally, suppose you have an attic space that has a floor in it that does not meet the requirements for s mezzanine, but you want to avoid it becoming a 'story' (requiring two exits, etc.). To avoid requirements for ‘story’ and in order to meet the definition of ‘attic’ (see 2006 IBC, Section 202 definitions) the attic space shall be limited only to maximum 4’ wide catwalks (see 2006 IBC, Section 410.3.2) that lead to equipment platforms (platform shall not exceed the size required for the equipment plus any required clearances for work area around access panels, etc.) – no ‘floor’ shall be permitted between the ceiling joists and roof rafters.
We find consulations, we learn tricks with which we deceive ourselves, but the essential thing - the way - we do not find. Listen to the river.

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