Hollow Core Concrete

We are almost done with our discussion on firestopping Hollow Core Concrete projects, but we can’t leave without sharing the last few common mistakes.

 

The real problem comes when the subcontractors run their pipes, ducts and cables without knowing that the mineral wool, concrete, grout or mortar is required.  Once these services are run, you are going to be hard pressed to actually firestop the installation properly.   Think about it for a moment. If you have a 7” core through the floor slab and you want to run  a 6” pipe (or a 4” pipe with 1” of insulation) in the hole, how are you going to get 4” of mineral wool into each side of the core (or possibly two cores that have been breached by the core rig.  That is when you are stuck with one of two really bad choices I noted earlier.

 

One more thing I should tell you before we are done. One AHJ I spoke with read the paragraph from the XHEZ document because he had been in one of our classes. He noticed that the thickness of the concrete had to match the requirements of the listed detail. He said, we have 4” of concrete so that should give us the minimum concrete required for a two-hour floor.  Unfortunately, if you speak with UL about this you will learn that this is not accurate. Here is why.  The topping slab cannot be considered as part of the rated assembly because when the rated assemblies are tested, there are no topping slab. Therefore, the performance of that material is not tested. This means it can’t be considered as part of the assembly.

 

These are not the only problems that you may encounter when firestopping in hollow core concrete, but they are the most commonly missed issues.  If you have a hollow core concrete project and you want to be sure you are not stuck with one of those two really bad choices, give us a call and we will be happy to help.  If you are in the area ,we can be on site and be part of your pre-con meeting.  If we can’t be there in person, we can call into a meeting and help your team plan ahead and avoid these issues.

 

There is a lot to consider in these last few blog posts, so if you prefer you can always hire us to help support your project.  Typically, we can provide a general oversight for much less than you would think. Past clients tell us we have made a colossal difference in the level of life safety. Would you like to see what we can do for you?

Give us a call!

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.

In our last post we discussed the firestop requirements for penetrations through hollow core concrete floors, we gave you a few examples of UL listed details that don’t require you to follow the requirements noted in the XHEZ

 

In the last blog, I said that I hoped you were getting this information in time.

 

Today, I want to explain why I made that comment. If you stick with us in the next post I will give you some ideas that might help your next project run more smoothly.

 

First, let me explain the problem you might face:

 

If your subs have run services half way up your building before they even think about what to do for the firestop installations, how are they going to get back in to the opening and fill those cells with any of the required material.

 

Here is a refresher of what is allowed:

Any cores breached by the opening need to be filled with min 4” depth of

• Min 4pcf mineral wool
• Ceramic fiber blanket
• Concrete
• Grout

 

So, let’s fix this before it becomes a problem.  The first step is DO NOT assume that everyone knows how to do this the right way.  Second step is to have a discussion, possibly at a pre-bid meeting, but certainly at a pre-construction meeting.

 

In this meeting, you need to make your team aware of the structural concerns related to a hollow core concrete floor, but you can’t forget to talk to them about firestop and here is what we suggest for the meeting.

 

• Print out the UL XHEZ document (give everyone a copy)
• Read the section on hollow core concrete in the meeting
• Explain what this means to all of your trades by giving specific examples based on the firestop submittals
• Put it in your meeting minutes in detail
• Completely review the firestop submittals against the penetrations you will have on the project (see our video series for more on how to do this)
• Conduct field walks before the trades run their penetrations to ensure the cells are filled if needed
• Then hold everyone accountable

 

If all of this sounds like a lot, I have good news.  The easiest way to be sure you have it right, is to hire us to conduct a pre-construction meeting with your team.  We will help get your team on the right page with what is required before they start and we will make a few field walks with the team as the project starts and progresses to be sure we are there to support any issues you may encounter.

 

If you want to do it right, we are a great addition to the team. Past clients tell us they are stronger on future projects because of what they learned working with us.

 

We are like a concentrated dose of support. Concentrated- stronger and more impactful because we focus on what we know and we share that with your team.  Clients who have worked with us in the past tell us the look at firestop differently and they believe the life safety of their future projects will always be better because of what they learned when we worked together.  Give it a try and see for yourself!

 

Our next post will give you a few more things to think about on your hollow core project when we discuss block outs. After that we will also share a few ideas on how to remedy the problem if you are reading this too late in the game.

 

Please share this information with anyone you think can benefit from it and if we can support your project in any way, give us a shout!

 

Until then, thanks for taking the time to read through this today.