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Losing the "exterior" sheathing argument

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

  1. Joe Engel

    Joe Engel Member

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    Anybody seen PE's using drywall inside as structural sheathing?

    Taking issue with structural sheathing exception for connecting studs to plates. New bank by local (NW Ms, seismic zone D) design firm and structural PE calls for truss roof with 12 foot, 2x6 walls and 1" non-structural foam to support 3" of closed cell foam. PE calls for 5/8 X drywall as structural sheathing on inside, all seams blocked, screws 8" and 12". I did get plywood corners by refusing to enter for inspection. Four Simpson strong walls on plan parallel to long dimension. I've asked for metal connections at stud to both top & bottom plates. PE says their not needed and it fill be fine once the drywall is installed (after black-in inspection). Load calc's over my head, asked for specific letter for file from PE siting code and materials used in design.

    Is this a new trend?

    Support the BCF!
     
    #1 Joe Engel, Dec 14, 2014
    Last edited by a moderator: Dec 14, 2014
  2. Sifu

    Sifu Gold Member

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    I see gypsum shear all the time. There are methods prescribed in the IRC chapter 6 for its use. I have not seen it as the sole method of lateral bracing but without looking it up I think it is in there. For a commercial building, I think chapter 23 covers the same. In any case, if the PE designs it based on those code sections and there are no blatant errors in his design......
     
  3. mark handler

    mark handler Sawhorse

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    Same value interior or exterior.

    The effective length of the wall and the shear running through other walls , and electrical boxes are the issue.
     
  4. ICE

    ICE Moderator

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    Assuming that's 4'x12' of brace. The shear value of that is quite large in comparison to drywall. What nail pattern did you specify?

    Depending on the size, they may be all that's needed and the drywall is icing on the cake.

    That and the plywood corners that you required have made you responsible for the design of the building. Not that I'm against that per se, but now that the bracing has been beefed up, you should analyze the anchor bolts.
     
    #4 ICE, Dec 14, 2014
    Last edited by a moderator: Dec 14, 2014
  5. MASSDRIVER

    MASSDRIVER Registered User

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    I'm curious how you can rationalize your own personal building requirements before an inspection?

    With all due respect, if I'm meeting the design and code, I might say pound sand. If you are using the bracing before entering as a safety blackmail I would start to think we're starting to play games or something.

    Brent.
     
  6. Sifu

    Sifu Gold Member

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    Not saying PE can't make a mistake but like ICE said, you might own the design if you modify the design, and do you have the authority to modify the design? My position is to assume the PE has a better understanding of the particular design conditions on the project he has submitted the design for. When I encounter a peculiar design I make sure they have followed it exactly and unless something seems to be missed or is contrary to the code I simply follow the design. In those cases where I may have questions I address them as just that-questions, but I don't add to or modify the design. That would be designing without the license or expertise to do so.
     
  7. ICE

    ICE Moderator

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    As an experienced inspector, he may have the expertise....and "We don't need no stinking license"
     
    #7 ICE, Dec 14, 2014
    Last edited by a moderator: Dec 15, 2014
  8. ICE

    ICE Moderator

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    Theoretically the structure should stand without the bracing in place. But there have been a few that I wouldn't recommend removing the plumb and line braces before starting the shear. A big, naked box could qualify for that.
     
  9. MASSDRIVER

    MASSDRIVER Registered User

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    I would agree, but that's a self-licking ice cream cone. I won't pull the plumb braces until sheared or permanent bracing is installed, and I won't yank the line braces until trusses and the diaphragm are locked up.

    Brent.
     
  10. Sifu

    Sifu Gold Member

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    As much as I would like to think my decades in the construction business have given me the equivalent expertise as the structural design firm and the PE, I am not sure the courts or professional engineering boards would agree. After re-reading the OP I am unsure of the main concern. Is it the use of gypsum for shear or the fact that there may not be adequate shear until the gypsum is applied? Without full knowledge of the conditions, both concerns may be valid and asking for a clarification on those points are valid. Maybe I read more into it than was intended. I do tend to cringe a little when an inspector seems to be trying to over ride a PE's design, though honest skepticism is always healthy.
     
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  11. mark handler

    mark handler Sawhorse

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    I agree. Build per approved plans and calcs.Trust but verify.....
     
    CityKin likes this.
  12. ICE

    ICE Moderator

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    There have been plenty of occasions that a building was built per the approved plans and it had a glaring flaw. When that happens I usually don't provide an alternative design. I inform them that the design as built didn't work and they need to provide a solution that will work. Sometimes it requires an engineer's approval but more often it's a less important mistake that I have seen many times.

    Tossing in shear wall segments on a new building is not an option.....it's fair game on a remodel.
     
    #12 ICE, Dec 15, 2014
    Last edited by a moderator: Dec 15, 2014
  13. mark handler

    mark handler Sawhorse

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    Trust but verify.....
     
  14. MASSDRIVER

    MASSDRIVER Registered User

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    Official credentials are key.

    That does not guarantee the design is error free by any means, and even though I may know the solution, and at times even provide the solution, It would be foolish for an inspectigator to approve it without someone with the proper education and expertise to green light the thing. Not my place.

    Brent.
     
  15. ICE

    ICE Moderator

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    It's a matter of degrees.

    The degree one holds. The degree of importance of the perceived problem. I simply can't send people to an engineer with every concern. After getting the same fix for a situation a dozen times, I think that I am on safe ground to apply that fix without asking the next engineer. Lots of jobs don't have an engineer involved on their side.

    Why should they pay an extra $500.00 for that MST-37?

    If the frieze blocks are nailed to the V-rustic, I know what to do.

    Stuff like that.

    That being said, Brent is more right than wrong and I wouldn't recommend doing what I do where you do what you do.
     
    #15 ICE, Dec 15, 2014
    Last edited by a moderator: Dec 15, 2014
  16. mark handler

    mark handler Sawhorse

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    Depends on what that strap is being used for and the loading; Blocking may not work
     
  17. ICE

    ICE Moderator

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    I usually add A-35s to the blocking and if the load is large it's a 60".

    Now I'm just being difficult. Truthfully, I don't like straps on blocks. Plates yes, blocks only if there is no other way.

    Anyway, the guy that started this thread wanted to hear about drywall as shear. I thought that went out with let-in braces but apparently not. So let's talk about value engineering.
     
    #17 ICE, Dec 15, 2014
    Last edited by a moderator: Dec 15, 2014
  18. mark handler

    mark handler Sawhorse

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    A35's don't work for a drag or uplift or post holddowns
     
  19. ICE

    ICE Moderator

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    Well if you can trust an engineer, they tend to keep a block in one place. How about an LPT4 then.
     
  20. Wayne

    Wayne Registered User

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    The architect or engineer is the one with the liability insurance for these type of situations.
     

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