• Welcome to The Building Code Forum

    Your premier resource for building code knowledge.

    This forum remains free to the public thanks to the generous support of our Sawhorse Members and Corporate Sponsors. Their contributions help keep this community thriving and accessible.

    Want enhanced access to expert discussions and exclusive features? Learn more about the benefits here.

    Ready to upgrade? Log in and upgrade now.

Area separation - mixed use M,B,R

A

azarch2010

Member
Joined
Jul 26, 2012
Messages
1
I am trying to determine if rated wall or floor assemblies are required in a mixed used building with retail space, business use and a residential component. The type of construction will be type five A. three stories and aprox 3000sf per floor. Cant find any requirement for separation but thought that the building departments required this. I did find that there is a requirement between the business use and the residential use of 1 hour. The common component is a floor which separates the residential from the business. The structure will be a rigid steel frame ( columns and beams) and the floor separating these two areas will be a concrete filled metal deck on steel beams.

The other separation is between floors between a retail space on first floor and a business use on the second floor.

Any help would be great.

PJ
 
Which building code and edition are you using for this project??

I take it the entire building will have a NFPA 13 system?
 
IBC

420.3 Horizontal separation.

Floor assemblies separating dwelling units in the same buildings, floor assemblies separating sleeping units in the same building and floor assemblies separating dwelling or sleeping units from other occupancies contiguous to them in the same building shall be constructed as horizontal assemblies in accordance with Section 711.

One hour required between a B or M occupancy and an R occupancy. All supporting construction needs to be one-hour rated
 
# ~ # ~ #

azarch2010,

Also, ...Welcome to The Building Code Forum ! 8-)

As **cda** has stated, ...see Table 508.4 in the IBC.........Footnote " a "

will direct you to Section 420.3, ...as **mtlogcabin** has provided.

Hope this helps !

BTW, ...which codes & editions are you using ?

# ~ # ~ #
 
I'm assuming the Group R occupancy is a Group R-2; if it's another Group R, then what I describe below may change.

This can be a nonseparated use building easily. Group R-2 is the most restrictive occupancy for Type VA construction at 12,000 sq. ft. per story and a maximum of 3 stories, which far exceeds the actual area you described even without any increases.

However, the Group R-2 will need to be separated from the other occupancies, as well as other dwelling/sleeping units, with fire partitions and/or horizontal assemblies per Chapter 7.
 
azarch....There happens to be a fantastic code consultant in your state^^^^^^ if you happen to ever need one.....And welcome to the forum!
 
IBC Table 601, Type VA construction, all of your floors (and attic separation) will need to be one-hour rated.

Therefore your bar joists would need either spray-applied fire-resistance or one layer of Type "X" gyp.bd.

Regardless of any exceptions you might find (none found in section 709.3) or the full NFPA 13 sprinkler system, I would still like to see at least a 60 minute rating for corridors and between living units. Using 5/8" drywall would essentially achieve that level of protection without having to call out fire partitions on the plans. It is important to have separate HVAC system for the corridors and separate HVAC for the stair shaft. PTAC units for each apartement would be a simple solution unless you are okay with having a row of condensor units located outside the building.

Locate a 24 x 24 rated shaft somewhere near the back of the building and extending up through the roof to accomodate a future kitchen exhaust hood in your first floor retail space. Ceiling radiation dampers for all supply diffusers and exhaust fans within the living units unless you can keep all of your ductwork below the drywall. Take your bathroom exhaust fans out to the exterior through 26 gauge round ducts and have the grills mounted in the wall rather than the ceiling = no damper required unless you decide to use flex duct. Same treatment for dryer ducts = no flex duct and make it easy to clean the lint out.

Do all of that. Call it done for the day. Pick it back up tomorrow.
 
Last edited by a moderator:
I agree that Chapter 5 has the answer to the OP. Within Chapter 5 there are two distinct paths to follow; separated mixed uses and non-separated mixed uses. For separated mixed uses the Code provides for a proportioning of space (the 'sum of the ratios' method). For non-separated mixed uses the 'most restrictive' method.

As noted above, the base requirements for Type VA in Chapter 6 will require a one hour floor/ceiling assembly.

Also as noted above the R occupancy will drive a sprinkler requirement throughout the building and will necessarily be a full NFPA 13 system.
 
mtlogcabin said:
Section 420 has specific requirements for separating R-1, R-2 & R-3 occupancies in addition to Chapter 5.
Click to expand...
Hence "Also as noted above the R occupancy will drive a sprinkler requirement throughout the building and will necessarily be a full NFPA 13 system."
 
JBI said:
...and will necessarily be a full NFPA 13 system.
Click to expand...
Not necessarily. I had this discussion with NFPA regarding a privatized student housing project (i.e. apartments) with a cafeteria and convenience store that was open to the public. I've heard a few sides of the argument, where one side states that NFPA 13R is acceptable throughout, one side states that only a NFPA 13 system is permitted, and one side that said a mix is allowed, provided that the public areas are on the ground floor and are separated from the upper floors using the horizontal building separation allowance per Section 510 (2012 IBC). Here's the response I received:

"NFPA 13R is permitted to be used for sprinkler systems in buildings of residential occupancy up to four stories in height. It is still permitted for use in buildings with incidental occupancies, provided the primary occupancy or use is residential. An example would be a hotel with a restaurant and gift shop. NFPA 13R can still be used throughout the building, as indicated in Annex Section A.1.1 provided the building is four stories or less in height and predominantly residential. The use of residential sprinklers outside of the residential portions may be limited per NFPA 13R, although an NFPA 13R system is still permitted throughout the entire building, even the spaces incidental to the residential occupancy.



"See Section 6.2.2 for locations where residential sprinklers can be used outside the dwelling unit. If residential sprinklers are not permitted in a portion of the building (a non-residential incidental occupancy), the sprinklers must still [be] quick response although the system as a whole is still considered designed in accordance with NFPA 13R."



Thus, for my example student housing project, a NFPA 13R could be used throughout, since the building is less than four stories, is predominately residential in nature, and the nonresidential uses are incidental to the main residential occupancy.

So, depending on the nature of the building in the OP (i.e. what is the relationship of the nonresidential to the residential?), a NFPA 13R system could possibly be allowed throughout.
 
You must log in or register to reply here.
Back
Top