Welcome back to our discussion about T ratings on floor assemblies.
Let’s talk about the construction types that have a floor/ceiling assembly. These break into two basic systems in my opinion there are wood framed construction projects and then there are those that are a combination of fluted metal deck, topped with concrete, supported by steel trusses and sheathed with TYPE C drywall on the underside (that is assuming the contractor is doing things right and not using typical type X drywall- but that is a whole different story.)
The current code has 7 exceptions where the T rating is not required to be met. Item 1 & 6 are metal /non-combustible penetrations items 2,3,4 are all electrical, 5 is fire sprinklers, and 7 allows the wood top plate to penetrate the ceiling membrane.
The exception is not here for tub/shower drains the way it was for the solid floor assemblies we talked about yesterday. What I don’t know is, do all the listed details have a T-rating for the membrane penetrations of these?
The ceiling membrane of 1- and 2-hour fire-resistance-rated horizontal assemblies is permitted to be interrupted with the double wood top plate of a wall assembly that is sheathed with Type X gypsum wallboard, provided that all penetrating items through the double top plates are protected in accordance with Section 714.5.1.1 or 714.5.1.2 and the ceiling membrane is tight to the top plates.
So, tell me, is this a technicality? Am I missing something?
The way I read this is that the assembly is a membrane penetration not a through penetration and when we go to the membrane section of the code it doesn’t allow I look forward to hearing your thoughts on this and what you allow in your projects.
In some ways it sounds like I am contradicting myself… or is the code doing that?
I really cant’ wait to hear what you all think!
