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Discussion Starter · #1 ·
I'm still in my design phase, but getting close to start construction. One thing I'm not sure exactly how to address is fireblocking while still keeping the walls decoupled from the concrete basement walls. I came up with this idea while thinking it over.




There will be insulation in between the studs. The wall header will be attached to the overhead joists (not shown) with RSIC-DC04 clips. It should yield airtight wall cavities meeting the requirements / intent of fireblocking while hopefully still being adequately mechanically decoupled from the concrete.


Is this going to work, or is there a better way to do this?
 

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Yep. Mineral works and it doesn't fully recouple things.
 

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Discussion Starter · #4 ·
Don't you have to compress the mineral wool in order to use it as proper fireblocking? How do you hold it in place?


Will a small bead of expanding foam really recouple the wall more than compressed insulation?
 

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Quote:
Originally Posted by Stereodude /forum/post/18300293


Don't you have to compress the mineral wool in order to use it as proper fireblocking? How do you hold it in place?


Will a small bead of expanding foam really recouple the wall more than compressed insulation?

Doesn't the expanding foam become rigid when it dries? The Roxul does not have to be compressed that much and it remains flexible. Not to mention AFB stands for Acoustical Fire Batt. Seemed like the best solution to me at the time.
 

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Quote:
Originally Posted by BIGmouthinDC /forum/post/18300384


Foams differ in the rigidity after curing. You want spongy.


Compressed insulation still has some springiness.

Big, you did it again.
 

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Discussion Starter · #8 ·

Quote:
Originally Posted by BIGmouthinDC /forum/post/18300384


Foams differ in the rigidity after curing. You want spongy.


Compressed insulation still has some springiness.

Do you have any pictures of where you put your mineral wool?
 

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I don't have a pic with the Roxul but here is what I did. See how this vertical and horizontal 5/8" sheetrock come together to form a firestop? Also notice how the top plate is decoupled form the joists with the DC04 clips leaving a gap? In order to decouple the two pieces of sheetrock, I cut down the vertical piece so it did not go past the top of the top plate. This left a gap that needed to be filled. I filled the gap with the roxul.

 

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I just friction fitted the mineral wool between the top plate and the exterior wall. You only need a few inches of the stuff for blocking. Wear gloves, a mask and goggles when working with the stuff. It just rains fibers. Very nasty to work with. Worse than OC703 and normal fiberglass.



 

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SD if I'm looking at that diagram correctly, you have planned foam behind each stud to the foundation as well as the top and bottom plates? If that's what the diagram shows, this will limit the wall movement and remove the goodness of decoupling.
 

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Discussion Starter · #12 ·

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Originally Posted by Ted White /forum/post/18301575


SD if I'm looking at that diagram correctly, you have planned foam behind each stud to the foundation as well as the top and bottom plates? If that's what the diagram shows, this will limit the wall movement and remove the goodness of decoupling.

I was thinking of every 10' (or so) for vertical studs (not every vertical stud), and along the top plate.
 

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Seriously, just go with mineral wool and use the foam in the non-soundproofed areas of the project. I used that crap in the other parts of the basement. One tip, don't get any on you. The stuff will bond with your skin and you'll lose a layer by the time you scrub it off.
 

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10' is a common requirement in a lot of places for vertical firestops. I only had 1 theater wall that was up against the foundation which meant only 2 vertical firestops. If yours is similar I really doubt it would matter much if you did sheetrock/firecaulk vs Roxul. However, If your layout is like Cathan's (I count 5 vertical firestops in just the 2 pics he posted) then Roxul all the way.
 

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Quote:
Originally Posted by Stereodude /forum/post/18301754


I was thinking of every 10' (or so) for vertical studs (not every vertical stud), and along the top plate.

That would concern me from a sound isolation perspective. We're counting on little impeding the movement of that inner leaf. That sounds like semi-coupling, which would raise the LF resonance point, dropping LF isolation.


The mineral fiber is a great way to go, really.
 
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