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


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 , ,

Exit Doors Must Open Out

August 27th, 2009

All exits doors must open out (in the direction of egress).

We all know that.   We’ve either seen a television show or read a magazine article about the deadly fire at The Iroquois Theatre in Chicago back in 1903.  We’ve been told that one of the causes of the high death count (602 people, 575 which perished within the first 20 minutes) was the exit doors opened inward and in the panic, people were trampled at the doors, blocking the exits.  It was said that bodies were piled 7 ft high in front of the doors.

Well exit doors do not have to always open out.  The International Building Code allows an exit door to open inward if the occupant load is less than 50 persons.  As always, the occupant load is determined by calculation using table 1004.1.1.  (Since 2006, the IBC does allow the Building Official to approve a lesser load than those determined by calculation.)

This rule is especially useful in cases where a small commercial space is directly on the sidewalk.  The IBC does not allow doors or windows to “open or project into the public right-of-way”.

Door opens onto large sidewalk.  Is this OK?

Door opens onto large sidewalk. Is this OK?

Note: While researching this article I wanted to define “public right-of way”.  Is it municipal property used for a sidewalk, street or alley?  Is it a sidewalk in front of a strip mall (private property)?  Is there a minimum width of a sidewalk?  I could not find a definition in the IBC even though it contains a chapter on encroachments into the public right-of-way.  Webster’s Dictionary also does not contain a definition.  I found a definition of “right-of-way” in the current City of Detroit Zoning Ordinance which stated “a strip of land occupied or intended to be occupied by a street, crosswalk, railroad, sanitary or storm sewer, electric transmission line…….”

Door on narrow sidewalk. Definitely not allowed.

Door on narrow sidewalk. Definitely not allowed.

Door opening onto walking area of private property.

Door opening onto walking area of private property.

My assumed definition has always been the municipally owned sidewalk, street or alley. I have always exempted strip malls from the door opening clause.

Myths & Legends ,

Dryer Ducts in a Shaft-A Case Study

June 21st, 2009

Recently, I performed a preliminary inspection on an eight story building whose upper 5 floors were being converted into residential lofts. Framing was near completion on one of the upper floors and trade work had been started. One of the first things I look at any residential use in a multistory building are:

  1. Where does the bathroom exhaust go?
  2. Are there clothes dryers and if so where do they vent? And…
  3. Where does the heating and cooling come from?

I am looking to see if shaft requirements have been met.
On this occasion I found both the dryer duct and the bathroom exhaust entering into a single shaft.  The bathroom exhaust was protected by a fire damper at its penetration to the shaft.  The 4’ dryer duct was only firestopped at its penetration.  The shaft and ducts terminated at the 7th floor where an undampered 10” duct penetrated the shaft and terminated at an exterior wall of the building. The building was of type 1B construction and was fully sprinklered.  The design was reviewed under the 2003 Michigan Existing Building Code.

Dryer Ducts in a shaft-c3

Smoke and Fire Dampers Required

Section 716.5.3.1 is very specific in requiring both fire and smoke dampers where ducts penetrate a shaft. There are many exceptions but none that allow either penetrations to be installed without a smoke damper.  Although the building code does not address dryer ducts, I know that dryer ducts cannot be dampered in any way. This would create surfaces for lint to accumulate and create a fire hazard.

Catch 22

While the State of Michigan had not adopted the 2006 International Building Code at the time, it had adopted the 2006 International Mechanical Code. Under the ICC, chapter 6 of the Mechanical Code and chapter 7 of the Building code have been nearly identical for the section on “Ducts and Air Transfer Openings”.  The 2006 now allows an exception for smoke dampers for dryer ducts, kitchen and bathroom exhaust in Groups R and B (previously this exception had only been for bathroom exhausts in B uses only). This exception is allowed under the following conditions:

  1. The building is sprinkled with an NFPA13 system.
  2. The openings into the shafts are installed with steel subducts at least .019 inch thick.
  3. The subducts must extend at least 22 inches vertically into the shaft.
  4. An exhaust fan is installed at the top of the shaft.  This fan must continuously run and be connected to an approved “standby” power source.

With some modifications (subducts and exhaust fan at top of shaft) this installation can bypass both the fire and smoke dampers. (There is an exception for fire dampers in any use group if you install subducts-provided there is a continuous airflow upward to the outside.  The only foreseeable problem is the 10 inch duct at the upper floor.  Subducting would be not be practical because of constraints of air flow, lint accumulation and height. The shaft could be continued horizontally to the exterior wall of the building bypassing any fire/smoke damper requirements.  The final issue is the renovation was reviewed under 2003 IBC and these changes do not exist in that code. The builder would have to apply for administrative relief through the local Authority Having Jurisdiction.

Articles ,

Elevator Lobbies

May 11th, 2009

On a recent visit of a renovation of a high rise building, I noticed smoke dampers installed in transfer openings in a wall which formed a required elevator lobby.  As the construction documents were approved under 2006 Michigan Building Code, an elevator lobby is required at each floor where an elevator connects 3 or more  stories.  Previously, International Building Code and Michigan Building Code required these lobbies only when the elevator opened into a rated corridor.


Existing 2-hr masonry walls formed 3 sides of the lobby and approximately 6 ft of metal stud wall made up the remaining wall which I was inspecting.  2 HVAC penetrations were made in this wall one was ducted and the other was the transfer grille.

IBC/MBC 2006 require the walls that make up this elevator lobby to meet the requirements of fire partitions.  There is an exception, when the building has an NFPA 13 or 13R fire suppression system, that allows these walls to be smoke partitions.  The design professional chose to take this exception.  Let’s review the requirements for both.


As you can see, the fire partition will require a 20 min door, a fire damper and some firestopping, but by using the exception and denoting the wall as a smoke partition a smoke damper will be required for the transfer grill.  Smoke dampers are a more costly item, not only for materials but for labor charges because of its motorization and activation requirements.  The cost of the smoke damper would greatly outweigh the costs of upgrading to a fire door and joint/penetration firestopping.

It Pays To Know $$$

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March 29th, 2009