Dear Architect- Why are you asking for a W rating
I have seen so many project specifications requiring a W rating. If you don’t know what a W rating is, please read this first. If you are already familiar with a W rating, do you know if it a requirement on your project? I recently looked at a wood framed project and there were W rating requirements. Clearly the architect has stock specifications that don’t take into account the fact that a wood framed project is NOT going to be capable of mitigating water movement in the way a concrete floor might.
But lets say you are dealing with a concrete floor, then W ratings are a viable requirement…except, when they are not.
Remember the test for a W rating is a three foot column of water that prevents even a single drop of water for 72 hours. If the specifications say as a blanket statement that a W rating is a requirement of floor penetration firestop systems, then what about a bundle of cables? What about MC cables? What about insulated pipes, the brackets to support the weight of multiple floors of pipes will break well below the three foot mark and how might one maintain the W rating with a break in the insulation, or with insulation that can’t hold back water such as fiberglass or other field installed insulations?
If you have been in construction for a while I am sure you can think of other examples when W rated firestop is not a reasonable requirement.
Im not saying stop asking for W ratings, because they are amazing. I could tell you some stories where they were a HUGE success. But be aware of the limitations and if you specify it, know what you are asking for. If you have a project that has W ratings specified and no one is asking questions, then my guess is they are not conforming with the specification.
If you have any questions feel free to contact us. We are happy to help if we are able.