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  1. #1
    AL Felmlee's Avatar
    AL Felmlee Guest

    Default Fire blocking basement

    I put this in another thread but this one might be a better fit:


    I have an interesting situation. I am building a home theater in the basement - below grade, masonary block wall.

    I have 1.5 inch rigid foam attached directly to the concrete wall and built a 2x6 framed wall against the rigid foam.

    the 2x6 framed wall is attached to the existing floor joists via resilence clip with a rubber washer. (the goal is to isolate the sound viberations from the house).

    I need to fireblock the 1.5 inch gap between the top plate of the wall and the foundation (made from the rigid foam board).

    The issue is that I cannot attach gypsum drywall to the top of the wall and the foundation without keeping the new wall isolated from the home.

    QUESTION: can i put a 1.5 inch strip of drywall on top of the 1.5 inch rigid foam and then firecaulk the edges. this will keep it isolated for sound.

    please see picture below in upper right corner







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  2. #2
    Join Date
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    Default Re: Fire blocking basement

    If the 1-1/2 inch thick rigid fiberglass fills the space between the walls no fire blocking is required. 2006 IBC 717 - Concealed spaces.

    Jerry McCarthy
    Building Code/ Construction Consultant

  3. #3
    AL Felmlee's Avatar
    AL Felmlee Guest

    Default Re: Fire blocking basement

    Jerry,

    my apologies- it is Owens Corning FOAMULAR XPS 250 not rigid.


    Sorry about that.

    Al


  4. #4
    Ted Menelly's Avatar
    Ted Menelly Guest

    Default Re: Fire blocking basement

    Foam directly on the block. Sleepers on the floor. Not really possible to monitor for water penetration into the cellar.

    Also if you are concerned with the fire blocking above the wall all you really need is some rated foam. This will also keep the media room isolated with the foam buffer. Not like it is a solid sound conductor. what do you plan on doing with the ceiling. Insulation, suspended drywall ceiling. This will isolate the media room from the first floor as well. Different density materials like sound board with drywall on top for the finish.

    Back many years ago I use to build sound rooms as well. Different technical keep popping up over the years. The different density boards is still one of the best sound insulators.

    Just some ideas


  5. #5
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    Default Re: Fire blocking basement

    Application Interior Foundation Walls

    "Fill band joist area with Flame Spread 25 or Curtainwall CW225 insulation."

    That's basically the area you are referring to.

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  6. #6
    AL Felmlee's Avatar
    AL Felmlee Guest

    Default Re: Fire blocking basement

    Thanks Ted,

    The sub floor is vented with air from the inside circulating through a dehumidifier in the next room. Under the subfloor is a humidistat that will turn in on and off.

    We have not had any moisture issues and the drain tile was put in both inside and outside but all run into a Sump in the next room, but I totally understand.

    Our sump pump (electricity went out while we were away) overflowed and that is why we raised the floor. In a closet area in the theater the floor can open up to monitor.

    The walls seam to be a mystery to insulate in a basement in Minnesota. If you talk to 20 different people, both inspectors and contractors you get 30 different answers. (strange)

    As for the ceiling I am using resilience clips and a hat channel. 2 layer of 5/8" drywall on ceiling and all 4 walls staggering the seams. Edges will be sealed with acoustical caulk. Insulation will be unfaced mineral wool in ceiling and walls. As i have it right now I can bang on the framed walls and my wife doesn't hear or feel it upstairs so it is a start.

    If I just tap on the original Joist alone, you can notice it pretty good all over the house.


  7. #7
    AL Felmlee's Avatar
    AL Felmlee Guest

    Default Re: Fire blocking basement

    Sorry, we since had a new pump, battery back up, and landscaped the entire yard. Sump ran very few times this summer.


  8. #8
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    Default Re: Fire blocking basement

    Al, that is a nice diagram. What software is that?

    Jim Robinson
    New Mexico, USA

  9. #9
    Ted Menelly's Avatar
    Ted Menelly Guest

    Default Re: Fire blocking basement

    mineral wool is what we always used. We could not find better. Sometimes it was blue board and 5/8 fire code or sound board and 5/8 fire code. Either way is worked very well. The sound board was best. Different densities breaks the sound up extremely well.


  10. #10
    AL Felmlee's Avatar
    AL Felmlee Guest

    Default Re: Fire blocking basement

    Jim - it was just powerpoint then I selected "all" and saved as a picture. Certainly not to scale but it worked when I got the building permit. I don't think basements needed a full architectural layout.


    Mineral wool is not the easiest to find but I have time. Not in a big hurry. I am not looking for a 100% soundproof room but would like to cut down as much as I can get for the tools I have and to code.


  11. #11
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    Default Re: Fire blocking basement

    Quote Originally Posted by AL Felmlee View Post
    Mineral wool is not the easiest to find but I have time.
    Need to specify what type of "mineral wool" insulation as "fiberglass insulation" is one type of "mineral wool" insulation. The other two types of mineral wool insulation are rock wool and slag wool insulation.

    Typically, when one is speaking of "mineral wool" insulation, they are referring to rock wool or slag wool insulation.

    Just mentioning that fiberglass *is* a type of mineral wool insulation, so just be careful that you order rock wall or slag wool insulation, not just "mineral wool" insulation.

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  12. #12
    AL Felmlee's Avatar
    AL Felmlee Guest

    Default Re: Fire blocking basement

    I was looking to use Roxul AFB Mineral Wool (was not sure if I can put a product name on this site)


  13. #13
    Richard Pultar's Avatar
    Richard Pultar Guest

    Default Re: Fire blocking basement

    you got a building permit and this information was not provided...a permit should not have been issued until this detail was clear on the plan.
    your little strip is not fireblocking
    run any idea you have past the inspector before you do the work .. once is enough
    I would put a strip of rock from the plate to the clip and fill voids with insulation . OR
    If you fill the joist cavity from the band or rim joist with insulation completely for at least the first 18 inches above the foam that eliminates the vertical horizontal issue.
    You only need to do this where the joists are perpendicular to the new walls.
    When the joists are parallel the the joist space is a continuation of the wall.


  14. #14
    AL Felmlee's Avatar
    AL Felmlee Guest

    Default Re: Fire blocking basement

    Thanks Richard,

    I will be filling the whole ceiling from Rim Joist to Rim Joist full of Mineral Wool (Roxul). 18 feet x 15 feet by 8-10" thick. It will overlap the gap between the framed wall and the concrete (1.5 inches where the foam seperates each) and every gap from the ceiling to the floor above.

    I am hoping that with Roxul being able to withstand 2150 degrees (F) it "should" be safer then most homes in the neighborhood.

    What I am running into is the inspector in the area is not really familiar with sound isolation from the main structure.

    I also know that it is his word that matters. I am just looking for ideas to explain the situation and hopefully a solution. I will call next week but since we were heading into the weekend, I couldn't sleep until I looked for some professional advise before I discuss.

    Thank you to everyone who has responded thus far. I do appreciate it.


  15. #15
    Ted Menelly's Avatar
    Ted Menelly Guest

    Default Re: Fire blocking basement

    Just give him the specs for the product. AS far as fireproofing I doudt that matters anyway. After all it was a basement in the beginning and anything could have burned down there. A separation is more than likely all you need at best. You do not have to have fireproofing between the first and second floor or 2200 degree rockwool as well. This is all for sound. The concern for fire proofing is way over kill. Do you plan on having a camp fire in the middle of the floor. What could you possibly do different down there that you would not do on the other floors.

    OOPs, maybe I should not ask

    For what it seems you have done so far I do not see any inspector having a problem with it. Just your typical inspections and wrap it up.


  16. #16
    Jeff Remas's Avatar
    Jeff Remas Guest

    Default Re: Fire blocking basement

    You should be fine with mineral wool in batt or blanket form or glass fiber.

    If you are not sure which product to buy, see if they have an ASTM E 119 rating.

    The bottom line however is that the material needs to be "approved" material which goes back to whatever the AHJ will accept. It is his/her call.


  17. #17
    Ted Menelly's Avatar
    Ted Menelly Guest

    Default Re: Fire blocking basement

    You know. I as just thinking. You are bringing the ceiling down to what. Clips, high hat or z channel, 2 layers of 5/8. You are going to be closing off all that space anyway. Plus you are insulating completely with rock wool. Other than maybe caulking some wire penetrations up through the top plate of the wall. Why would you have to do anything else. You are taking car of all concerns anyway.


  18. #18
    AL Felmlee's Avatar
    AL Felmlee Guest

    Default Re: Fire blocking basement

    Ted,

    You are correct. I am basically making a human aquarium completely sealed. I have and exterior door frame (sealed), with an indoor solid door slab to help with sound escaping.

    I will have sofits built after the room is completely sealed in 2 layers of 5/8 drywall. The sofits will also have 2 layers of 5/8 drywall and HVAC using acoustical flex tubing that will run through the sofit so there is no sound penetration.

    The issue is that the gap within the framed wall the the foamular creates at the top of the wall. I am thinking that the combination of a 1.5 inch 5/8 drywall with fire caulk and Mineral wall on top of that would be decoupled from wall frame and like I said "should" be good since the mineral wall will be blanketed over the area of interest.

    here is a picture of what I am looking at. I guess I will know more this week.




  19. #19
    Richard Pultar's Avatar
    Richard Pultar Guest

    Default Re: Fire blocking basement

    the little strip is a waste of material and effort. It does not meet the codes requirement that
    the strip is to be self supporting ie independent of the space. If the plastic ever burned it would just become part of the goo.
    the insulation above the gap is a code proper draftstop without any more stuff.
    If I was you I'd stop trying to figure this out any more and stop explaining what your doing.
    Just do it.

    Soft surfaces and nonparallel surfaces are what you want .


  20. #20
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    Default Re: Fire blocking basement

    Fireblocking, firestopping, even draftstopping, none of those apply there. There is no gap to firestop/fireblock/draftstop. That is solid filled (as shown in the drawing).

    What does apply there is:

    From the 2006 IRC. (underlining is mine)

    - R314.4 Thermal barrier. Unless otherwise allowed in Section R314.5 or Section R314.6, foam plastic shall be separated from the interior of a building by an approved thermal barrier of minimum 0.5 inch (12.7 mm) gypsum wallboard or an approved finish material equivalent to a thermal barrier material that will limit the average temperature rise of the unexposed surface to no more than 250°F (139°C) after 15 minutes of fire exposure complying with the ASTM E 119 standard time temperature curve. The thermal barrier shall be installed in such a manner that it will remain in place for 15 minutes based on NFPA 286 with the acceptance criteria of Section R315.4, FM 4880, UL 1040 or UL 1715.


    Worst case scenario: "foam plastic shall be separated from the interior of a building by an approved thermal barrier of minimum 0.5 inch (12.7 mm) gypsum wallboard", which is precisely what Al is contemplating using ... except that instead of planning on using 1/2" gypsum board he is planing on using 5.8" gypsum board (which is even thicker).

    Now, if ... *IF* ... there was no foam to fill the stud cavities, then, yes, fireblocking at the ceiling would be required. But there is foam insulation in the stud cavities, effectively blocking the entire stud cavity.



    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  21. #21
    Jeff Remas's Avatar
    Jeff Remas Guest

    Default Re: Fire blocking basement

    Superior Walls uses an exposed foam insulation that is approved through a Legacy report for exposure.

    I don't know of any others that are. Fill me in if you are aware.

    It is a DOW product but not all DOW products have that approval.


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