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Holes in CMU between townhomes

Discussion in 'Residential Building Codes' started by jar546, Nov 4, 2019.

  1. jar546

    jar546 *****istrator

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    They punched holes in the CMU between townhomes in order to fit new electrical boxes for a level 2 renovation. Then, filled the gaps with cheap foam. Thoughts?
    F71147DD-2C03-40B6-A823-FFF7571D7EF4.jpeg
     
  2. Ty J.

    Ty J. Sawhorse

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    Looks like this would be classified as a membrane penetration and not a through penetration; although, that is a bit of a fuzzy line with masonry walls. A bit of professional opinion may apply when differentiating between membrane or through penetrations in CMU walls.

    Per the following code section (R302.4.2), membrane penetrations are limited to boxes that have been tested for use in fire-resistance-rated assemblies and are installed per their listing (see red highlighted text below).


    R302.4.2 Membrane penetrations
    Membrane penetrations shall comply with Section R302.4.1. Where walls are required to have a fire-resistance rating, recessed fixtures shall be installed so that the required fire-resistance rating will not be reduced.

    Exceptions: (NOTE THAT NUMBERING IS OFF)
    1. Membrane penetrations of not more than 2-hour fire-resistance-rated walls and partitions by steel electrical boxes that do not exceed 16 square inches (0.0103 m2) in area provided that the aggregate area of the openings through the membrane does not exceed 100 square inches (0.0645 m2) in any 100 square feet (9.29 m2) of wall area. The annular space between the wall membrane and the box shall not exceed 1/8 inch (3.1 mm). Such boxes on opposite sides of the wall shall be separated by one of the following:
    1.1. By a horizontal distance of not less than 24 inches (610 mm) where the wall or partition is constructed with individual noncommunicating stud cavities.
    1.2. By a horizontal distance of not less than the depth of the wall cavity where the wall cavity is filled with cellulose loose-fill, rockwool or slag mineral wool insulation.
    1.3. By solid fire blocking in accordance with Section R302.11.
    1.4. By protecting both boxes with listed putty pads.
    1.5. By other listed materials and methods.
    1. Membrane penetrations by listed electrical boxes of any materials provided that the boxes have been tested for use in fire-resistance-rated assemblies and are installed in accordance with the instructions included in the listing. The annular space between the wall membrane and the box shall not exceed 1/8 inch (3.1 mm) unless listed otherwise. Such boxes on opposite sides of the wall shall be separated by one of the following:
    2.1. By the horizontal distance specified in the listing of the electrical boxes.
    2.2. By solid fireblocking in accordance with Section R302.11.
    2.3. By protecting both boxes with listed putty pads.
    2.4. By other listed materials and methods.
    1. The annular space created by the penetration of a fire sprinkler provided that it is covered by a metal escutcheon plate.
     
  3. e hilton

    e hilton Bronze Member

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    Thoughts? The6 did a poor job laying out the outlets, had to cut twice. Would have been better to use a shallow quad box with a duplex cover, that would give enough cu in for the wire and device and not impact the cmu.
     
    jar546 likes this.
  4. mtlogcabin

    mtlogcabin Sawhorse

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    Is the rating at the CMU wall or the gypsum board? Is it sprinkled and the rating is now one-hour for a common wall in lieu of the two-hour assembly that may have originally been required? As mentioned is it just a membrane penetration?
     
  5. steveray

    steveray Sawhorse

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    How many CCC? Derating? Crazy foam no good for fireblocking....
     
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  6. cda

    cda Sawhorse

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    I like to take a piece of the foam ,,,

    What they call fire stop, fire caulk, whatever


    And light it off and show what a great fire starter material it is!!!
     
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  7. e hilton

    e hilton Bronze Member

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    I don’t know the answer in this case, but there is a difference between burning and sustaining. When you take away you match, does the foam continue to burn? Or does the flame go out?
     
  8. cda

    cda Sawhorse

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    Continues
     
  9. Builder Bob

    Builder Bob Sawhorse

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    Don' think Great stuff foam is allowed except for wood frame residential construction.... see the listing for Great stuff. Don't think it is allowed for masonry construction or for two hour fire resistant construction.
     
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  10. steveray

    steveray Sawhorse

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    The rating is one thing, but it seems like the foam is used for fireblocking which would also not be allowed.....
     
  11. jar546

    jar546 *****istrator

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    So as far as I am concerned, the block wall must be maintained without any penetrations and all equipment must be surface mounted so they have to fill in the holes they created as to not reduce what was existing.
     
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  12. north star

    north star Sawhorse

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    $ ~ $

    Remove the non-approved foam........Use copious amounts
    of mineral wool and seal with fire rated caulking.

    $ ~ $
     
  13. cda

    cda Sawhorse

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    I hate mineral wool almost as much as foam.

    Anyone have a UL listed diagram to post, showing mineral wool and fire caulk.
     
  14. Paul Sweet

    Paul Sweet Sawhorse

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    What is the required rating of the block wall? Most block will still have a 1-hour rating with a penetration on one side.
     
  15. cda

    cda Sawhorse

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    My guess no fire sprinklers??
     
  16. jar546

    jar546 *****istrator

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    The OP pic is non-sprinklered townhouse which would require 2 hour fire separation. If it were sprinklered then 1 hour.
     

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