Our last blog post discussed clearance requirements for sprinkler pipes when you are working in a seismic zone. The NFPA and the damper manufacturers use the phrase clearance. The firestop industry uses the term annular spaceand defines it as the distance from the outside edge of the penetrating item to the inside edge of the opening in the rated assembly.
Firestop applications often refer to a minimum and maximum annular space. This is because most of the times the pipes are not centered in the opening. This is not going to cause a problem with most applications, but when we look at the NFPA requirements discussed in the last post we used the example of an 8” sprinkler main that would require a 12” opening.
If the pipe is centered in the opening the firestop detail will require roughly 2” annular space. This is not typically going to be an issue, but when reviewing the firestop submittals you need to make sure the annular space of the firestop details will conform with this code requirement. But that is not realistic to have the pipe centered in the opening all the time. If you want to prepare for the worst-case scenario, which would be the pipe slammed all the way to one side of the opening then you have to be sure your firestop submittals allow for this.
If the pipe is completely askew you may have as much as just shy of 4” of annular space o contend with. Well, really it will be less because even if you have an 8” pipe and a 12” opening the outside diameter of an 8” steel pipe is going to be close to 8-1/4” so that would make the maximum annular space around 3-3/4.
Most firestop manufacturers have fantastic websites to help you find the details you need or you can call them directly and talk to their tech team for additional support.
When you are conducting your firestop submittal review you need to be sure that your firestop details can meet this requirement, or that you have seismic couplers on both sides of your rated walls and floors and any “non-frangible” substrate.
Two other things to look for when comparing the firestop detail to the field condition:
- Sleeve: Did the use a thin gauge tin sleeve? Is that allowed by the detail? Firestop details often list a sleeve as optional, but some don’t allow (sleeve is not listed) or some require it. If a sleeve is allowed or required check to be sure the gauge in your paperwork matches what they used in the field. The fire dynamics of a thin gauge sleeve will be different from that of a heavier gauge sleeve so they may need to be treated differently. So, to make this simple for you just remember, you need to look for 2 things:
- Is the sleeve allowed or possibly required?
- Does the gauge match?
- Support Bracket: If firestop is smeared all over the bracket that means that it was in place when the firestop was installed. That seems basic but it means that the firestop may not be installed properly. Check back on our next post for more details on this.
If you have problems or questions, don’t hesitate to contact us for help as well.