W Rating: Dear Architect, Why Are You Asking for It?

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. The architect’s standard specifications do not anticipate the challenges posed by water movement in wood-framed projects, unlike concrete floors.

But lets say you are dealing with a concrete floor, then W ratings are a viable requirement…except, when they are not.

The test mandates a three-foot column of water to remain drop-free for 72 hours. If floor penetration firestop systems require a W rating, what about a bundle of cables? What about MC cables? How can the W rating be maintained with insulated pipes? Brackets supporting multiple floors of pipes often fail below three feet. What should be done if insulation breaks or if materials like fiberglass, which may not effectively block water, are used?

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.