Question on ICC Construction Type Classification - Table 601

Comments

3 comments

  • Avatar
    David Kaplan

    Aleksandar,

    Let me see if I can help you out here.  The term "non-combustible" does not equal "fire rated."  Just because something is constructed out of non-combustible materials does not mean that it has a fire rating that can last 1, 2, or 3 hours.  An example would be a  Type IIB building.  If you look at Table 601, you see that IIB is 0 HR rated everything, but it's entire non-combustible.  So, that would be a building whose walls are constructed of metal studs and not wood, but is allowed to have exposed steel roof joists, exposed steel columns and beams, etc.  Let's use a typical warehouse building - you'd look up and see all the bare steel structure fully exposed.  Steel as a material is non-combustible, in that when burned it does not contribute to the spread of a fire (which is the definition of non-combustible).  However, if you were to burn an exposed steel beam for a certain amount of time, eventually it will yield, deform, and fail.  It therefore is not "fire rated," unless, you protect it with an additional measure of protection.  That's where the fire ratings come into play.

    If you have to do a Type IA building, for example, you now not only have to construct your building out of non-combustible materials, but the elements listed in Table 601 must now also be fire rated.  Let's take that same warehouse example but build it out of IA construction.  If you look around that building, you'll likely see fireproof spray on all the beams, joists, and columns in the building.  That fireproof spray provides the additional fire rating of protection (in this case 3 HRs) for that non-combustible element.  The intent here is that should the steel beam be exposed to fire, it will now NOT yield, deform, and fail for at least 3 hours.  I have therefore protected the primary structure of this building for 3 HRs to allow people inside that much additional time to get out.  In the prior IIB example, that structure is not rated at all, so people in that warehouse are not afforded this same level of protection. 

    The Code allows you to build your building out of IIB when the building's area and height are within the limits set forth in Chapter 5.  If you meet those height and area limits for a IIB building, Code is telling you "OK, this building is not so big and not so tall that we are going to require you to provide an additional fire rating protection of the structure.  People will be able to get out safely based on this building's size and height."  In a IA scenario, your building is either bigger or taller than allowed and Code is therefore telling you, "This structure needs to be rated because you are beyond the limits where an unprotected structure is acceptable.  You need to make it so this building will stay standing long enough for people to get out."

    A non-combustible building in general is safer than a combustible (wood) building, even if the structure of the buildings is 0 HR rated, because the materials used within do not contribute to the spread of fire.  The fire takes much longer to spread in a IIB building than in a VB building, and thus this is why Chapter 5 identifies that a IIB building can be built much bigger than a VB building in most if not all instances. 

    Hope this helps.

    6
    Comment actions Permalink
  • Avatar
    Beatriz Juan Miranzo

    Beautiful explanation, thank you so much! 

    0
    Comment actions Permalink
  • Avatar
    SHASHIKALA PEDDAGOPU

    Very good explanation, thanks David

    0
    Comment actions Permalink

Please sign in to leave a comment.

Powered by Zendesk