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Continuous insulation versus gypsum sheathing

Discussion in 'Commercial Energy Codes' started by Hyrax4978, Oct 18, 2019.

  1. Hyrax4978

    Hyrax4978 Registered User

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    Has anyone come up with a good way to fasten siding to a metal framed building and using continuous insulation with gypsum sheathing?

    Seems as though metal framed walls need some amount of continuous insulation these days.

    It appears most gypsum sheathing products say they are not nailable or screwable and you need to hit a stud.
    How will an installer guarantee hitting a stud when installing metal panel siding or cementitious siding when there is rigid insulation and sheathing hiding the studs.

    Is this a case of shop drawing coordination between trades, or is there a product that is nailable or screwable that will allow fastening and maintaining continuous insulation.

    Someone suggested Z furring at the rigid insulation but that negates the continuous insulation.

    Any help, thoughts or details much appreciated.

    Thank you,
     
  2. steveray

    steveray Sawhorse

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  3. Hyrax4978

    Hyrax4978 Registered User

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    Looks like plywood sheathing is not allowed in type IIB construction. Only furring strips for siding or the siding themselves in certain applications.
     
  4. steveray

    steveray Sawhorse

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    If it is not "structural" sheathing it is "blocking".....CT has gone that way in the past....Call OSBI....

    STATE BUILDING CODE INTERPRETATION NO. I-12-03 August 11, 2003 The following is offered in response to your request for a formal interpretation of the provisions of the BOCA National Building Code/1996 portion of the 1999 State Building Code as it pertains to the use of combustible materials in buildings of Type 2C construction.

    Question 1: Plywood meeting the flame spread requirements of Section 803.2 and Table 803.4 is used as an interior wall finish applied directly to metal studs in a nonrated interior wall in a Type 2C building. The wall is constructed between manufacturing space (Use Group F) and office space (Use Group B) in a nonseparated mixed-use building. The wall does not create a corridor. Is this application code compliant?
    Answer 1: The answer to this question depends on whether or not the plywood is a structural component of the wall in question. If the plywood is required for structural reasons (for instance to brace studs in a load-bearing wall), then Section 603.1 and Table 602 do not permit its use within a building of Type 2C construction. If, on the other hand, the plywood is non-structural and used as interior finish only, it would be allowed providing it meets the flame spread requirements of Section 803.4 and meets the requirements for a Class III material as required by Table 803.4 for rooms or enclosed spaces in Use Groups B and F.

    Question 2: Can fire-retardant treated wood be used for blocking in metal stud walls for lavatory accessories and to stiffen door jambs in metal stud walls?
    Answer 2: Yes. Item 8 of Section 602.4.1 allows the use of combustible nailing or furring strips in non-combustible construction in accordance with Section 804. BOCA formal interpretation number 30/401/84 states “it is the intent of the code to permit the use of combustible nailers and blocking within Types 1 and 2 construction.”

    Question 3: Can non-fire retardant treated plywood be used for EIFS backer board in lieu of exterior gypsum in areas where needed for the installation of building signage? Answer 3: Yes, assuming the EIFS manufacturer approves of its use as an integral part of their system. Keep in mind that there is a limitation placed on the amount of combustible wall finish of 10 percent of the exterior wall surface area where the fire separation distance is five feet or less.
     
  5. steveray

    steveray Sawhorse

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    Can you call it IIIB?
     
  6. RLGA

    RLGA Sawhorse

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    Typically, the sheathing is installed first over the studs. Then a weather-resistive barrier is applied over the sheathing, followed by the insulation. The insulation can be adhered, attached with fasteners, or with z-furring

    Usually, cladding is then installed over the insulation using a cladding support system attached through the insulation into the studs. These support systems are varied in design and some have thermal break designs (fasteners are separated from the metal system with nonmetallic isolators). In lieu of a cladding support system, z-furring can be installed horizontally as the insulation is being installed. This does provide a bit of a thermal bridge but only at the fasteners, but there are some manufacturers that make a nonmetallic z-furring that can support a cladding load.

    If anchored masonry veneer is used, the anchors are attached before the insulation is installed...sometimes before the weather-resistive barrier is installed if the barrier is fluid-applied. The anchors will protrude through the insulation at the joints between insulation boards (continuous insulation boards are commonly provided at widths that will accommodate typical anchor spacing). Some anchor manufacturers provide anchors with thermal break designs.
     
  7. Paul Sweet

    Paul Sweet Sawhorse

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    What kind of siding? I found out the hard way on a house I built that wood siding directly applied over foam insulation warps like crazy. HardiePlank might do better.

    The best (and hardest) way is to install furring over the insulation and nail or screw the siding to the furring. It takes some measuring and a little trial & error to get the furring over the studs.
     
  8. Hyrax4978

    Hyrax4978 Registered User

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    Thank you ALL!
    I will touch base with OSBI this week to verify they are good with that older interpretation with the current code. I assume they should be ok with it.

    I think my other option is to just use a furring system over the rigid insulation. using Z furring while installing the insulation negates the "continuous" that the code appears to be looking for these days.

    Thank you all for your help!!!
     
  9. Hyrax4978

    Hyrax4978 Registered User

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    Just a follow up/FYI.
    the composite panels in the link above are not available in New England.
    Thank you,
     
  10. Tim Mailloux

    Tim Mailloux Registered User

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    I have used non-structural fire treated plywood sheathing on CT State projects for the exact reasons you mentioned. Its never been an issue with OSBI, and they review every phase of the project and do all the on-site inspections for state projects.
     
  11. mark handler

    mark handler Sawhorse

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    jeffc likes this.

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