Firestopping Hollow Core Concrete- Part 4
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 arises when subcontractors run their pipes, ducts, and cables without realizing they need to include mineral wool, concrete, grout, or mortar. Once they complete the installation, you will struggle to firestop it properly. Think about it for a moment. If you have a 7” core through the floor slab and want to run a 6” pipe (or a 4” pipe with 1” of insulation) through the hole, consider how you will fit 4” of mineral wool on each side of the core. You might also face the challenge of dealing with two cores that the core rig has breached. That’s when you face one of the two really bad choices I mentioned 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. You cannot consider the topping slab as part of the rated assembly because testers do not include topping slabs when they test rated assemblies. Therefore, they do not test the performance of this material. As a result, you cannot include it as part of the assembly.
You might face other problems when firestopping in hollow core concrete, but you often miss these common issues. If you have a hollow core concrete project and want to avoid those two really bad choices, give us a call. We’ll 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 in to help your team plan and avoid these issues.
Consider all the details from these last few blog posts. If needed, you can always hire us to 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?