Firestopping Hollow Core Concrete- Part 3

Welcome back to our discussion about firestopping hollow core concrete. If you are still with us, then we hope it is because you want to make sure your next hollow core concrete project runs smoothly and that the firestop installations conform to requirements.


The topic today- BLOCK OUTS


When firestop is not part of the pre-construction discussion on a hollow core concrete project, typically the openings sizes cavalierly exceed 7”x7” that you now understand as a typical requirement. This means the opening may not be firestopped without additional documentation.  Larger openings can cause other complications as well because of the unique nature of the floor.  Assuming you can get the necessary paperwork that may not be a big deal. By necessary paperwork we are talking about a listed detail allowing for an opening larger than 7”x7”, or an engineering judgement (EJ) from the firestop manufacturer that is unique to your firestop installer AND unique to that project. See IFC guidelines for EJ’s.


When it comes to block outs, people typically think the only thing they have to do is have a conversation with the structural engineer, but now you know that is not the ONLY thing you need to do.


Here are some things to consider:


  • How many block outs do you have planned on your project?
  • Are they larger than 7”x7”?
  • How are you going to firestop each of them?
  • Do you have a listed detail for each application?


You need to have a plan for how you are going to protect these block outs.  How you are going to maintain the fire rating of the floor once you make a hole in it.


Clearly the easiest thing for larger block outs, is to protect them with a shaft.  This eliminates the problem of firestopping them in the first place, but now you need to be sure you are going to firestop any shaft penetrations properly. We have shared a rather exhaustive discussion on how to firestop shaft applications properly in past blog posts.


Let’s break this down a little bit. Openings are not allowed to be larger than 7”x7” (or 7” diameter). The only exception is, if the opening is protected by a shaft.  But don’t forget that a shaft has to have a top and a bottom and if there will be a penetration through either of these, you will need to firestop this as well. Now you are falling back to the issue of finding a firestop detail applicable to that installation.


Typically, if your opening is larger than 7”x7” you will require an Engineering Judgement from the firestop manufacturer.   Then you have to ensure the installation conforms with whatever is required in that document.  That is unless you are in New Jersey, like me, where EJ’s are prohibited according to DCA (Department of Community Affairs). That is unless they go through as alternate means and methods (if your AHJ will allow it) or if they are approved by a third-party testing laboratory.  This can get complicated, so be on top of this when you start your project so you know how this will be handled in your jurisdiction.


Check back on our final post when we share a few common mistakes. If you have any questions about what we have shared so far, please reach out to us. We are happy to help if we are able.