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?