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    Fire-stopping Draft-stopping CMU/Frame Construction

    Fire-stopping Draft-stopping CMU/Frame Construction

    New postby Tampatundra on Fri Jun 16, 2017 7:00 pm

    Please take a quick look at the two pictures I've attached.

    Subject: 2 story new home construction (Florida) with CMU first level, Framing second level

    Do you see anything wrong with either picture?

    The horizontal 1x4 furring strip on the 1st floor (CMU wall) is attached on top of the RMAX foam insulating board. Is this acceptable for fire blocking or draft stopping.
    The horizontal 2x4 furring strip on the 2nd floor (Frame Construction) is attached directly to the studs and the RMAX is under the furring with additional furring running vertical.

    I am unable to find the code reference that specifically details the requirement, if any, for fire-stopping or draft-stopping for this particular scenario.

    Any assistance will be greatly appreciated.

    Fire1sm.JPG


    Fire2sm.JPG
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    Re: Fire-stopping Draft-stopping CMU/Frame Construction

    New postby Jerry Peck - Codeman on Sun Jun 25, 2017 10:33 pm

    Tampatundra wrote:The horizontal 1x4 furring strip on the 1st floor (CMU wall) is attached on top of the RMAX foam insulating board. Is this acceptable for fire blocking or draft stopping.


    First is it "fire blocking or draft stopping"? It is "fireblocking", 2014 FBC-Residential: (underlining is mine)
    - R302.11 Fireblocking.
    - - In combustible construction, fireblocking shall be provided to cut off all concealed draft openings (both vertical and horizontal) and to form an effective fire barrier between stories, and between a top story and the roof space.
    - - Fireblocking shall be provided in wood-frame construction in the following locations:
    - - - 1. In concealed spaces of stud walls and partitions, including furred spaces and parallel rows of studs or staggered studs, as follows:
    - - - - (Jerry's comment: In "wood-frame" construction, and wood furring strips adds wood framing to the inside surface of the CMU walls; additionally, R302.11 Item 1. specifies "including furred spaces", and the wood furring makes those spaces "furred spaces". This is an AHJ decision as some AHJ can't get past "wood-frame" to the "including furred spaces", while other AHJ do get to the "including furred spaces". This makes those "furred spaces" on the inside the CMU walls as "combustible construction ... concealed draft openings" which require "fireblocking".)
    - - - - 1.1. Vertically at the ceiling and floor levels.
    - - - - 1.2. Horizontally at intervals not exceeding 10 feet (3048 mm).
    - - - 2. At all interconnections between concealed vertical and horizontal spaces such as occur at soffits, drop ceilings and cove ceilings.
    - - - 3. In concealed spaces between stair stringers at the top and bottom of the run. Enclosed spaces under stairs shall comply with Section R302.7.
    - - - 4. At openings around vents, pipes, ducts, cables and wires at ceiling and floor level, with an approved material to resist the free passage of flame and products of combustion. The material filling this annular space shall not be required to meet the ASTM E 136 requirements.
    - - - 5. For the fireblocking of chimneys and fireplaces, see Section R1003.19.
    - - - 6. Fireblocking of cornices of a two-family dwelling is required at the line of dwelling unit separation.

    Now that the above identifies those "furred spaces" as requiring fireblocking, we go to permitted fireblocking materials.

    Also from the 2014 FBC-Residential: (underlining is mine)
    - R302.11.1 Fireblocking materials.
    - - Except as provided in Section R302.11, Item 4, fireblocking shall consist of the following materials.
    - - - 1. Two-inch (51 mm) nominal lumber.
    - - - 2. Two thicknesses of 1-inch (25.4 mm) nominal lumber with broken lap joints.
    - - - 3. One thickness of 23/32-inch (18.3 mm) wood structural panels with joints backed by 23/32-inch (18.3 mm) wood structural panels.
    - - - 4. One thickness of 3/4-inch (19.1 mm) particleboard with joints backed by 3/4-inch (19.1 mm) particleboard.
    - - - 5. One-half-inch (12.7 mm) gypsum board.
    - - - 6. One-quarter-inch (6.4 mm) cement-based millboard.
    - - - 7. Batts or blankets of mineral wool or glass fiber or other approved materials installed in such a manner as to be securely retained in place.
    - - - 8. Cellulose insulation installed as tested for the specific application.
    - - R302.11.1.1 Batts or blankets of mineral or glass fiber.
    - - - Batts or blankets of mineral or glass fiber or other approved nonrigid materials shall be permitted for compliance with the 10-foot (3048 mm) horizontal fireblocking in walls constructed using parallel rows of studs or staggered studs.
    - - R302.11.1.2 Unfaced fiberglass.
    - - - Unfaced fiberglass batt insulation used as fireblocking shall fill the entire cross section of the wall cavity to a minimum height of 16 inches (406 mm) measured vertically. When piping, conduit or similar obstructions are encountered, the insulation shall be packed tightly around the obstruction.
    - - R302.11.1.3 Loose-fill insulation material.
    - - - Loose-fill insulation material shall not be used as a fireblock unless specifically tested in the form and manner intended for use to demonstrate its ability to remain in place and to retard the spread of fire and hot gases.
    - R302.11.2 Fireblocking integrity.
    - - The integrity of all fireblocks shall be maintained.
    - (Jerry's comment: I could not find "foam plastic" in the above, nor could I find "foam plastic insulation" within the sections addressing insulation. Foam plastic is required to meet specific surface burning and smoke developed limitations, and all thermal insulation is required to be basically in substantial contact with the backside of the interior surface.)

    The horizontal 2x4 furring strip on the 2nd floor (Frame Construction) is attached directly to the studs and the RMAX is under the furring with additional furring running vertical.


    Both of the above conditions with the foam plastic insulation under the furring creates an additional "furred space", while at the same time not being an approved fireblocking material for dividing the spaces up into areas which are fireblocked 'at the ceiling', 'at the floor', and 'horizontally at maximum spacing of 10 feet- see above R311 item "1.2. Horizontally at intervals not exceeding 10 feet (3048 mm)." This includes measuring around corners – all furred spaces have a 10 maximum horizontal spacing between vertical furring strips which need to be fully block off each 10 foot maximum space from floor to ceiling.

    Here is an additional item I noticed:

    - The first photo and the hanger with what appears to be the bottom chord (and end) of a floor truss – is that a spacer behind the back of the floor truss? If so, the truss is too short for the span (the span may have been widened - accidentally or intentionally - without reconfiguring the truss which spans it) and is not sufficiently bearing in the hanger, the hanger is not attached to the floor truss - the hanger is only attached to the shim/blocking behind the truss.
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    Re: Fire-stopping Draft-stopping CMU/Frame Construction

    New postby Tampatundra on Mon Jun 26, 2017 5:19 pm

    1. Is the downstairs block construction considered combustible construction?
    2. Can the drywall serve as the fire blocking? Normal 1/2" Gypsum Drywall

    What I'm inferring from your response is that RMAX foam board insulation is not a listed fire blocking material, and therefore the horizontal furring should be attached directly to the block/CMU wall to provide the necessary fire blocking required. (side note: RMAX does make a fire rated foam board insulation, but for this application, is not that type)

    As for the floor truss: good eye there! I did not catch that. The installer properly attached the shim to the engineered truss.

    Your response would be appreciated. Thank you
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    Re: Fire-stopping Draft-stopping CMU/Frame Construction

    New postby Jerry Peck - Codeman on Mon Jun 26, 2017 8:03 pm

    Tampatundra wrote:1. Is the downstairs block construction considered combustible construction?


    The block is not, but the wood furring is. That is what I was referring to that it is the AHJ call - does the building official deem the wood furring to be as addressed in the code "including furred spaces" or does the building official ignore the combustible wood furring and deem it as not combustible? Some places used metal furring, that solves the combustible construction aspect, however, most still use wood furring, as in your photos.

    2. Can the drywall serve as the fire blocking? Normal 1/2" Gypsum Drywall


    If installed where fireblocking is required, but not when used on the face of a wall - fireblocking is for the concealed spaces, so the 1/2" gypsum board would need to be used in the concealed spaces for the purposes stated in R302.11.

    What I'm inferring from your response is that RMAX foam board insulation is not a listed fire blocking material, and therefore the horizontal furring should be attached directly to the block/CMU wall to provide the necessary fire blocking required. (side note: RMAX does make a fire rated foam board insulation, but for this application, is not that type)


    Even 'fire rated foam boards' would not be suitable for use as "fireblocking" ... unless they were tested and listed for that use, and labeled with something to the effect of 'Suitable for use as fireblocking' (I have not seen any RMAX listed for use as fireblocking so I am just guessing at the wording which would be used).

    As for the floor truss: good eye there! I did not catch that. The installer properly attached the shim to the engineered truss.


    What does "properly attached the shim" mean? How many nails, what size, what spacing, what species of wood, are there any uplift loads on those trusses that would need to be transferred to the hangers, etc (this would be specified in the truss engineering)? Is the shim and its attachment rated for the bearing of the truss?
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    Re: Fire-stopping Draft-stopping CMU/Frame Construction

    New postby Tampatundra on Wed Jun 28, 2017 6:22 pm

    Jerry,

    Thank you again, for your quick and thorough response. It is much appreciated.

    In conclusion, regarding the horizontal furring on CMU construction:

    Picture 1 shows the RMAX installed against the CMU wall, and the horizontal 1x4 furring installed on top of the RMAX. Is this a code compliant installation? Or, does the horizontal furring need to be installed onto the CMU wall, and the RMAX up to the bottom of the 1x4 furring?

    "the draftstopping referred to in the code statement is the concealed space" But, the concealed space is filled with the RMAX foam board insulation (in the example whereby the RMAX is installed on top of the RMAX.

    Thank you.
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    Re: Fire-stopping Draft-stopping CMU/Frame Construction

    New postby Jerry Peck - Codeman on Wed Jun 28, 2017 7:11 pm

    John,

    Tampatundra wrote:In conclusion, regarding the horizontal furring on CMU construction:

    Picture 1 shows the RMAX installed against the CMU wall, and the horizontal 1x4 furring installed on top of the RMAX. Is this a code compliant installation?


    No, not with wood furring, which makes that combustible construction.

    Or, does the horizontal furring need to be installed onto the CMU wall, and the RMAX up to the bottom of the 1x4 furring?


    Yes, that would resolve that part of the issue as the wood furring would serve as the fireblocking.

    "the draftstopping referred to in the code statement is the concealed space" But, the concealed space is filled with the RMAX foam board insulation (in the example whereby the RMAX is installed on top of the RMAX.


    A couple of different things on that part:
    - a)
    - - The code addresses stud spaces/furred spaces/concealed spaces filled with various types of insulation as follows, and foam plastic insulation is not one of those listed: (underlining is mine)
    - - - R302.11.1.1 Batts or blankets of mineral or glass fiber.
    - - - - Batts or blankets of mineral or glass fiber or other approved nonrigid materials shall be permitted for compliance with the 10-foot (3048 mm) horizontal fireblocking in walls constructed using parallel rows of studs or staggered studs.
    - - - R302.11.1.2 Unfaced fiberglass.
    - - - - Unfaced fiberglass batt insulation used as fireblocking shall fill the entire cross section of the wall cavity to a minimum height of 16 inches (406 mm) measured vertically. When piping, conduit or similar obstructions are encountered, the insulation shall be packed tightly around the obstruction.
    - - - R302.11.1.3 Loose-fill insulation material.
    - - - - Loose-fill insulation material shall not be used as a fireblock unless specifically tested in the form and manner intended for use to demonstrate its ability to remain in place and to retard the spread of fire and hot gases.
    - - (Note that nothing in the code accepts rigid foam plastic insulation as being a suitable replacement for fireblocking, thus proper fireblocking is still required when rigid foam plastic insulation is used.)
    - b) With the RMAX under the furring strips, wood or metal furring, the foam plastic insulation would not be in substantial contact with the drywall, the energy code addresses the location of insulation as basically being in substantial contact with the backside of the interior wall (I don't have the precise wording right now) and the code addresses foam plastic insulation and its protection (to reduce the risk of spread of fire).
    - c) With the RMAX under the furring strips, wood or metal, and then a second layer of RMAX fills the space behind the drywall, there is still the fireblocking issue as the foam plastic is not listed as a suitable fireblocking material.
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