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Existing Home Garage Conversion to ADU

Discussion in 'Residential Fire Codes' started by PC_Number, Aug 16, 2019.

  1. PC_Number

    PC_Number Registered User

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    Problem:
    Existing 2 story home would like to convert the existing 1st floor Garage to ADU. Code section R302.3 requires a 1-hr floor assembly between the two dwelling units, and 1-hr rating at the supporting construction. What have you seen as design solutions. People will not want to reconstructed the floor assembly to create the 1-Hr rated assembly.
    One possible solution is shown in the link below:
    https://www.portlandoregon.gov/bds/appeals/index.cfm?action=getfile&appeal_id=14189&file_id=14773

    I am looking for a tested listed and approved retrofit 1-hr fire rated floor assembly or any creative solutions.
    Any help or insight would be greatly appreciated.
     
  2. ADAguy

    ADAguy Sawhorse

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    Doing this as: owner, AOR, contractor or other?
    Who people, don't want to?
     
  3. cda

    cda Sawhorse

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    Welcome

    There are other Calif’s on the site
     
  4. cda

    cda Sawhorse

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    IEBC enforced??
     
  5. cda

    cda Sawhorse

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  6. ADAguy

    ADAguy Sawhorse

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    Good background but doesn't address his question.
     
  7. PC_Number

    PC_Number Registered User

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    I am a plans examiner. Just wondering what other jurisdictions have approved in the past. The problem is creating a 1-Hr fire separation at the ADU and Main Dwelling units between the 1st and 2nd floor without having to redo the second floor framing to create a listed 1-hr rated floor and ceiling assembly.
     
  8. cda

    cda Sawhorse

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    Not into design, but how about something like shaftliner?

    https://cache1.buildgp.com/wp-content/uploads/2018/11/DensGlass-Shaftliner-shaftwell-stairwell-systems-technical-guide.pdf


    Does your city have any written guidance on ADU,,

    or just use base code?
     
  9. mark handler

    mark handler Sawhorse

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  10. ADAguy

    ADAguy Sawhorse

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    How about if you add sprinklers?
     
  11. Pcinspector1

    Pcinspector1 Platinum Member

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    Good info Mark!
     
  12. Pcinspector1

    Pcinspector1 Platinum Member

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    I assume you've looked at the GA-600-2015 for gyp systems?
     
  13. PC_Number

    PC_Number Registered User

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    Good Idea with the Shaft Liner I was thinking along the same lines but shaft liners are for "walls". I have looked into the gypsum association listed assemblies. Again, they have a lot of approved wall assemblies but not much for floor rated assemblies.
     
  14. cda

    cda Sawhorse

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    Not into all that design stuff,

    But does the code just require one hour seperatation ??


    Base code not calif

    R302.3 Two-family dwellings.
    Dwelling units in two-family dwellings shall be separated from each other by wall and floor assemblies having not less than a 1-hour fire-resistance rating where tested in accordance with ASTM E 119 or UL 263. Fire-resistance-rated floor/ceiling and wall assemblies shall extend to and be tight against the exterior wall, and wall assemblies shall extend from the foundation to the underside of the roof sheathing.
     
  15. mtlogcabin

    mtlogcabin Sawhorse

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    What do you have for floor joist? Dimensional lumber or I-Joist?
    16" or 24" OC spacing
     
  16. PC_Number

    PC_Number Registered User

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    We have dimensional lumber.
    CDA: Look at section R302.3.1 Supporting Construction.
    This requires elements that support the 1-Hr Fire Rated Assembly to get the 1-hour rating too.
     
  17. Pcinspector1

    Pcinspector1 Platinum Member

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    Support beam and post will need to be protected that supports the floor above. Do you have access to a gypsum catalog for a 1-hr protection design?
     
  18. mark handler

    mark handler Sawhorse

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    State says they are not required unless the main house has them
     
  19. mtlogcabin

    mtlogcabin Sawhorse

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    If the joist are 16" OC then you can use IBC chapter 7 other wise it is not hard to find one hour floor ceiling assemblies
    Remember the fireside is the ceiling and 2 layers of type X or C is all most assemblies use
    The fireside for supporting construction in the conversion of the garage is the interior side so again it will be a simple single or double layer to achieve this unless CA have amended the IRC
     
  20. ADAguy

    ADAguy Sawhorse

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    Not required but can't they be used in lieu of 1 hr?
     

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