Archive

Archive for September, 2009

Separation between dwelling units and non-residential occupancies

September 10th, 2009

As you may remember, in the 2006 edition of The IBC section 419 was a new addition which provided scoping requirements for horizontal and vertical separations between dwelling or sleeping units in I-1, R-1, R-2 and R-3 Occupancy classifications.  The one-hour separation requirement had always been in Chapter 7 of the IBC but now there was a directive to send you to Chapter 7 when checking on special requirements for the occupancies in question.

Now in 2009, the IBC has added that the same “between-unit” requirements be met between these occupancies and others.  Why is this important?  In some instances, the previous versions of the code would allow you to have no fire-resistance-rated separation between say a manager’s office and the apartment next to it.  Let me give you an example:

7000 sq ft, Type 3B Construction

7000 sq ft, Type 3B Construction PLAN VIEW

Let’s take a 7000 sf building, with 5000 sf of 1st floor area and 2000 sf on the second floor.  The second floor contains 2 apartments.  In 2006, section 419 sends you to 719(fire partitions) and 711(horizontal assemblies).  Both of these sections talk about ratings for walls or floors separating dwelling units (or sleeping units).  It did not require any separation between dwelling units and other occupancies other than the requirements for separated occupancies in Table 508.3. Now, we’ll say we are going to put in a BBQ restaurant in our building with solid fuel grilles.  The Code allows us to have non-separated occupancies if the building does not exceed the most restrictive building area and height limitations (from Table 503) for the occupancies in question.  We have an R-2 which is allowed to be 16,000 sf and 4 stories and an A2, which is allowed to be 9500 sf and 2 stories.  Since the A2 is the most restrictive and our building has not exceeded this, no separation is required under 2006 IBC.

2006 IBC only required 1-hr separation between dwg units

ELEVATION

We could have an open ceiling with open floor joist between the restaurant and the apartments. (The requirements for the Sound Transmission Class requirements, oddly enough, have always required a “sound” separation (STC 50) between dwelling units and “public or other service areas”.)

All this changes in 2009.  Language has been added to require the 1-hr rating between dwelling or sleeping units and “other occupancies contiguous to them in the same building”. Now a minimum 1-hr rated floor ceiling assembly would be required between the restaurant and the apartments.

2009 IBC now requires at least a 1-hr horizontal separation between the lower level bar and the second floor apartments

2009 IBC now requires at least a 1-hr horizontal separation between the lower level bar and the second floor apartments

As before, in Types 2B, 3B and 5B, these separations can be reduced to ½ hr in buildings equipped with an NFPA 13 sprinkler system. (Has anybody figured out a ½ hour wall yet?)

Frank Bayer

New in 2009 , ,