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Looking for an inventive way to fireblock in an unfinished part of a basement right under an upstairs tub (regular cast iron).

I won't bother with a picture because too much going on. But the "hole" is a ~18"x18" square that includes the tub drain, part of the tub, and the interior wall it is attached to (guessing this is what got it dinged).

Underneath it... wow... main stack, every water run in the house, electrical, the main I beam... and under that is a walkin closet. So there is (bottom to top) a walkin closet then a mess of stuff above it in a cavity then the hole to the tub.

Cannot really put anything on the adjoining walls due to the mess of pipes, almost zero wood to secure it (pipes are that close) and electrical... This is the first time in 20+ years I have been flagged for a firestop in the middle of a house!

Suggestions, questions, creativity needed or I am going to have to build a big box and section of a ceiling to cover this area...

Let's complicate matter even more... the square I need to fireblock... it is basically out of reach. No tool will get in between the pipes and there is a solid 2 feet of cavity - emptiness from bottom of pipes to the square.

Note: Was explicitly asked not to use spray foam by inspector.

DMoore
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    fireproof foam sealer? – Jasen Mar 08 '21 at 11:03
  • I'd think that pictures, even if they don't show the complete situation, would help people visualize & offer better solutions. You know, picture === 1000 words and all that... – FreeMan Mar 08 '21 at 12:51
  • Dmoore can you slip strips of sheet metal up and into place? Then using sealing clay around the drains and any electrical. I have to do this on commercial multistory for a wire chase at each floor. I have been allowed to use sheet metal and i notch for pipes and electrical overlapping the strips and in some cases cover with red fire rated foam. I use fire stop clay so contact with the wires and pipe is not an issue and will usually cut a few extra holes that are filled with fire stop also. – Ed Beal Mar 08 '21 at 14:54
  • @Jasen - good question! Just read the report - inspector specifically asking for us to not use spray foam. Very interesting as I have not seen a "remark" on an inspection explicitly exclude something that should meet building code. I am guessing he saw the mess there and didn't think we would be able to seal that volume - guessing the general cavity is ~2'x2'x2'. What sucks is whatever I put there will for sure make new home owners life harder in future. – DMoore Mar 08 '21 at 14:59
  • @EdBeal - well that is my first thought. But think... I get strips maybe 10" wide.... Got to screw them in using a 2' bit while trying to hold the metal in place (with broomsticks?). Then I have to apply clay to the edges and cracks using a self fabricated robot arm? This was my first thought but no idea how I can attach it. – DMoore Mar 08 '21 at 15:04
  • dMoore I have a long handle power driver for putting up wires to hang suspended ceilings and wire trays. I have used this a time or 2 put the charge shell in and the nail drill a hole in the tin and push up the charge sets the fastener in wood or concrete (I use gray/brown for wood) don’t use red /yellow on wood they can almost blow the washer but that’s how I do it, make sure not to leave any powder charges on the floor 100.00 fine for each one (or that’s what it is here). I can’t remember the name but it was something like ceiling master , you push up and it sets the fastener. – Ed Beal Mar 08 '21 at 15:47
  • I found a tool called lagmaster plus but it is much larger than my unit, I got it at platt 30 years ago and it still works. I think I have a Ramset L1600 ceiling master , I found the parts breakdown but not the tool yet – Ed Beal Mar 08 '21 at 15:57
  • @EdBeal - calling inspector. I am going to try to convince him to just shove rock wool up there. Anything else will be a travesty for the new owner. – DMoore Mar 08 '21 at 16:16
  • That may work if they can’t see an air passage. I haven’t been called on that unless 3 stories in residential. – Ed Beal Mar 08 '21 at 16:20
  • The obvious answer, since foam was disqualified, is shotcrete. ;-) – Greg Hill Mar 08 '21 at 21:37
  • Is the cavity more than 10’ long? If not, then nothing is required. – Lee Sam Mar 08 '21 at 22:37

2 Answers2

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I was surprised that any fire blocking is required in single family residences. I had to look it up.

Section R602.8 requires it for “all concealed draft openings (both vertically and horizontally), to form effective barrier between stories, and between top story and roof space.” Also required at “openings around vents, pipes, and ducts at ceiling and floor level.

Approved materials are in Section 602.8.1 and includes: 1) 2” nominal lumber, 2) 2 layers of 1” nominal lumber with lap joints staggered, 3) 23/32” structural panels (plywood), 4) or 3/4” particle board, 5) 1/2” gypsum board, 6) 1/4” cement board, 7) batts or blankets of mineral or fiberglass is approved for compliance with the 10’ horizontal fire-blocking in walls constructed using rows of studs, but must be held in place. “

Also, Section R602.8.1.1 says “unfaced fiberglass batt insulation shall fill the entire cross section of the wall cavity to a minimum height of 16” measured vertically. When piping is encountered the insulation shall be tightly packed around the obstruction.”

Lee Sam
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Interesting call with inspector and thankfully got a guy who knows his stuff and not looking to be a jerk.

Me: Bob (fake name). Got this big hole in my unfinished ceiling with a mess of stuff around it. You can barely even see the cut out (you have to be at the exact right spot and angle to see it), how did you see the wall exposed?

Bob: I see everything haha.

Me: You going to make me enclose that whole area. You know that will screw over the new homeowners bigtime. (main stack, half the plumbing in the house, few electrical runs... all inaccessible)

Bob: I am not supposed to give advice but enclosing it does seem to hurt next home owner.

Me: So I can just stuff the thing with rock wool?

Bob: That seems like an option.

Me: OK good, that is like a whole batt but I will put it up there.

Bob: Well that would have about triple the fire rating as you throwing up some flashing or sheetrocking around it.

Me: OK thank you. Was going to ask you if the city had a 2' drill extension it would let me borrow.

So answer: stuffing cavity with insulation (fire rated).

Just to be clear was a pain in the ass this location is I don't think I can get the roxul in unless I cut it in pretty small squares. This will take 20-30 mins.

DMoore
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