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Losing the "exterior" sheathing argument

Discussion in 'Commercial Seismic' started by Joe Engel, Dec 14, 2014.

  1. mark handler

    mark handler Sawhorse

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  2. Joe Engel

    Joe Engel Member

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    Thanks Brent for the Contractors perspective, I've been on that side of the fence, too. I really appreciate all the input. It's the location of the "Sheathing" that raises hair on my neck. With foam on the outside and drywall an the inside, I have to trust that drywall was installed as prescribed in the plan. It most likely will be fine and the PE is the one that's liable, I just hate to sign off on something I can't verify.

    I'm not a PE just 30 years OJT in Light Frame construction, why I'm recommending and not requiring. I try to assume the position of applying the code instead of enforcement. The OSB corners were suggested to me by the super & framer long before the trusses were even delivered; I just encouraged their use by letter to GC who was also in favor. The four Simpson SW24x12x6's may do the job well, I'm just "old school" and don't trust drywall hangers for critical seismic connections. Again, I'm concerned for potential of a trend in eliminating the exterior structural sheathing.

    Color me Gray...
     
    CityKin likes this.
  3. conarb

    conarb Registered User

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    Joe:

    You are correct, walls have to breathe, permeable barriers don't work, if you put sheetrock on the inside foam on the outside will create the dreaded dual barrier, otherwise known as the mold sandwich. I never install plywood on the exterior and never install OSB period, if the engineer calls for it I get permission to install plywood on the interior behind the sheetrock, I am now moving to full red iron frames on my better homes. Another thing I would do is go back to installing diagonal 1x8 boards on the exterior, that's what I learned to do before plywood was available and it worked fine, the mills don't mill it anymore but my lumber yard says they will run 2x8s through their resaw bandsaw for me.

    Interestingly I built a lot of apartment projects in the 60s and into the early 70s, many three stories + penthouse over a class A garage with the only bracing the sheetrock, in our earthquake zone there have been no problems to my knowledge., but I sure see pictures of failures after earthquakes, I guess I've just been lucky.
     
  4. Mark K

    Mark K Platinum Member

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    Personally I will not use drywall to resist lateral loads but this does not give the inspector the right to impose his personal beliefs. Rather than rely on the design engineer the building department should have the design reviewed by a licensed engineer as part of the plan review process. I would not be surprised if such a review would result in changes.

    Any building department that does not have the ability to have a professional engineer plan check the structural design has problems. You have the authority to perform a thorough plan check so exercise that authority and have an engineer review the structural design. Enforce the building code, but the inspector should not impose his personal beliefs.

    Building inspectors typically have deep knowledge regarding some portions of the code but this does not mean that they have total knowledge about all aspects of the building code.

    Inspectors do pick up a lot of knowledge but this does not give them “…the equivalent expertise as the structural design firm and the PE…”. The reality is that the training and knowledge that a professional engineer has provides him with a different insight than can be obtained by performing inspections. Any inspector that believes otherwise is deluding himself.

    At least in California it is clear that if a building official or inspector were to practice engineering they need to be licensed.
     
  5. MASSDRIVER

    MASSDRIVER Registered User

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    Agree will all aforementioned and would applaud reasonable solutions to problems, especially with all parties on board.

    But it is a new day.

    Solving problems is no longer the issue. CYA is. And architects have so much language in their contracts absolving them of responsibility that they are covered by a 10' thick lead blanket.

    Even failure of a sketchy design will inevitably fall on the builders shoulders.

    Brent.
     
  6. mtlogcabin

    mtlogcabin Registered User

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    It is a fine line between a "peer" review by an AHJ's engineer and the AHJ's engineer telling the design engineer it won't work, submit a new design

    Ultimately whatever was "approved has to be followed in the installation and if an inspector cannot allow enough time to follow the installation then a third party should be required on site for continual inspection to verify the installation was done according to the design.
     
  7. Mark K

    Mark K Platinum Member

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    The AHJ's engineer does not provide a peer review rather he checks for compliance with the code. A peer review generally deals with issues that may be of concern to the Owner but are not within the scope of the building code.
     
  8. JBI

    JBI Registered User

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    If it is a prescriptive design then the Code path must be clear.

    If it is not prescriptive then the DPR must provide the relevant documentation.
     
  9. north star

    north star Sawhorse

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    ~ & ~ & ~



    Joe Engel,

    Simpson-Strongtie DOES have area representatives to assist in Shear & Seismic

    designs, ...on Commercial & Residential applications.

    If you want, I have contacts that service your area.......Of course they will

    charge you for a review of your project, and they will want to sell you their

    products.............As an option, they DO have PE's and others on their staff.

    You could certainly discuss your project with the Area Rep for FREE !

    Just sayin'...



    ~ & ~ & ~
     
  10. Joe Engel

    Joe Engel Member

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    Update: Sealed/Signed letter hand delivered today. PE has reviewed the plan and is now calling for 4 inch spacing on drywall nails instead of 8, Simpson RSP4's 4 foot O/C for seismic, and a special inspection to verify nail pattern on drywall before finisher can begin. Super says it will increase the cost about $1000 on a $1.35 million job. This is way more than I expected, I guess I owe the PE a Christmas card.

    Thanks to all for comments and suggestions... Support the BCF, where else can you get 20+ GOOD opinions in 4 days!!!
     
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  11. JBI

    JBI Registered User

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    Gotta love it when it all comes together in harmony... Good call by the AHJ and a proper response by the DPR.
     
  12. Sifu

    Sifu Gold Member

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    Vindication! Seems to have worked out well for everyone. BTW, we do drywall inspections only when used for shear, usually limited to a few locations or if rated assembly. Otherwise we assume they have fastened it prescriptively.
     
  13. kingalucpanel

    kingalucpanel Registered User

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    I agree.This still need to examine.
     

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