I give up! I've looked everywhere. I'm wiring a hotel with rooms back-to-back. I know I'm not allowd to have back to back penetrations in a firewall, but what is the min. distance between openings. According to the general we need to maintain a 1hr fire rating, I'm not even sure that is right.
Fire wall
- Thread starter binney
- Start date
- Status
renosteinke
Senior Member
- Location
- NE Arkansas
Buliding code specifies 24", and not in the same stud bay.
Strathead
Senior Member
- Location
- Ocala, Florida, USA
- Occupation
- Electrician/Estimator/Project Manager/Superintendent
You are not looking in the right place. Fire walls are a rated assembly, usually listed. That said, the information you are looking for is included in the UL listing for the various assemblies. It can be easily found in most fire stopping catalogues, such as 3M, or Hilti. It can also be found on most gypsum board manufacturers web sites etc. We can proabably answer your question making likely assumptions, but, number of boxes, size of openings, etc. determine the real answer. So look it up and you will be able to argue your point this time and forever. (teach a man to fish and all)
Strathead
Senior Member
- Location
- Ocala, Florida, USA
- Occupation
- Electrician/Estimator/Project Manager/Superintendent
Really? Which building code and where. I do not recall that being in NFPA 101 or the Florida Building Code. I do see that is specifications regularly, but that is also the guideline for back to back boxes without fire pads only for the listed assembly most commonly used. Generally the building codes require a listed 1 hour assembly period. They don't dictate how to assemble it.
It surprises me to see that I should be looking in UL. I've spent several hours reading endless articles from the NFPA. I see the answer of 2 feet. I've used that actually on multi-familly units, but I'm not sure what they were requiring for a fire wall. If it's in the building code, where in the building code? I'm from WI and I've searched high and low through our state codes and couldn't find anything.
renosteinke
Senior Member
- Location
- NE Arkansas
This issue comes up regularly, and it's time to post the actual source.
Most places - the "Left Coast" being the exception (surprise!) are currently on the 2006 IBC. The matter is discussed in section 712.3.2, or "penetrations" in the "fire resistance rated construction" section.
In part, this section makes an EXCEPTION - that is, no special measures, not even putty pads, are required for electrical boxes provided ALL of the following details are met:
1) The box is no larger than 16 sq. inches. Box depth and mud ring type do not matter. the common 4-S complies. The 4-11 does not;
2) The total area of the actual openings does not exceed 100 sq. inches for a 100 sq, ft. wall area. Turn a corner and you're into a different wall area. Each single-gang opening uses somewhat less than 15 sq. in.;and,
3) the box / mud ring face is not set back more than 1/8." This is already part of the NEC.
The above addresses openings on one face of the wall. What about 'back-to-back?'
The same section of the IBC continues:
If the wall has boxes through both sides of the wall, the boxes must be separated by one of the following:
1) At least 24" of horizontal spacing. This has the effect of saying 'different stud bays;
2) A separation at least as wide as the wall is thick, if that space is packed with mineral wool;
3) Solid fireblocking. Thus, a solid wood stud separating stud bays would suffice;
4) Putty pads on both boxes; or
5) Other listed means.
I have simplified the requirements and added my own comments. I strongly reccomend that you visit Bulk Resource, or some other site, and view your State's adopted version of the IBC. Most jurisdictions will have ammendments to the 'model' codes they adopt.
Most places - the "Left Coast" being the exception (surprise!) are currently on the 2006 IBC. The matter is discussed in section 712.3.2, or "penetrations" in the "fire resistance rated construction" section.
In part, this section makes an EXCEPTION - that is, no special measures, not even putty pads, are required for electrical boxes provided ALL of the following details are met:
1) The box is no larger than 16 sq. inches. Box depth and mud ring type do not matter. the common 4-S complies. The 4-11 does not;
2) The total area of the actual openings does not exceed 100 sq. inches for a 100 sq, ft. wall area. Turn a corner and you're into a different wall area. Each single-gang opening uses somewhat less than 15 sq. in.;and,
3) the box / mud ring face is not set back more than 1/8." This is already part of the NEC.
The above addresses openings on one face of the wall. What about 'back-to-back?'
The same section of the IBC continues:
If the wall has boxes through both sides of the wall, the boxes must be separated by one of the following:
1) At least 24" of horizontal spacing. This has the effect of saying 'different stud bays;
2) A separation at least as wide as the wall is thick, if that space is packed with mineral wool;
3) Solid fireblocking. Thus, a solid wood stud separating stud bays would suffice;
4) Putty pads on both boxes; or
5) Other listed means.
I have simplified the requirements and added my own comments. I strongly reccomend that you visit Bulk Resource, or some other site, and view your State's adopted version of the IBC. Most jurisdictions will have ammendments to the 'model' codes they adopt.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Went to the WI Commercial Building Code website - then did a search for "fire wall penetration separation", found this on the 6th result:
"Section IBC 715.4 shall be referenced to address opening protection in fire walls."
Many places are now on the 2009 IBC, but the same information is in Section 713.3.2 in the 2009 edition. This comes from exception 1 in that section and only applies to steel boxes. For plastic boxes, you need to go to exception 2 which requires the boxes to be listed and refers to their listing for use in fire rated walls.
This also applies to steel boxes. The requirements in exception 2 for plastic boxes are nearly the same, but item 2 can't be used for plastic boxes, unless of course, the listing of the specific box allows something like that. I have seen some that do.
- Location
- Simi Valley, CA
What Reno said.
I think that Allied has boxes that are listed that reduced the back to back spacing to 3" and they also have a 3 gang box that is listed for a rated wall.
Remember that your fire pads have to also have a sound transferance rating of 50 or higher. Also you have to use a box and conduit for your low voltage.
Oh and steel boxes do not need to have a fire pad any where other than where required. Some jurisdictions make you fire pad them.
I think that Allied has boxes that are listed that reduced the back to back spacing to 3" and they also have a 3 gang box that is listed for a rated wall.
Remember that your fire pads have to also have a sound transferance rating of 50 or higher. Also you have to use a box and conduit for your low voltage.
Oh and steel boxes do not need to have a fire pad any where other than where required. Some jurisdictions make you fire pad them.
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