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  1. #1
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    Dec 2005
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    Default Top plates - IRC R602.3.2

    This section says the double top plate joints need to be staggered 24 in. Then the picture says if they are not 24 in, you need to use splice plates per 602.3.2.

    Problem is, there is nothing about the splice plates in 602.3.2. There is a description of a plate in "Exceptions", having to do with single top plate construction.

    Has anyone got an explanation or clarification of how this section is supposed to work?

  2. #2
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    Default Re: Top plates - IRC R602.3.2

    With the use of wider wall framing, used to allow thicker insulation in the walls, a desire to reduce materials led to the allowance of a single top plate alternative. The exception allows the use of a single top plate in bearing and exterior walls as long as adequate top-plate ties are used. In addition, ceiling joist or rafters need to line up as close as possible to the verticle studs in the wall. The top-plate ties have to be a minimum of 3 inch x 6 inch x 0.036 inch thick galvanized steel plate, nailed to each segment by six 8d nails on each side of the splice.
    If you are using a double top-plate and can not offset the joints in the two plates by at least 24 inches, you are allowed to splice the top-plate using the 3x6x.0.036 galvanized plate.

  3. #3
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    Default Re: Top plates - IRC R602.3.2

    Quote Originally Posted by Dave R View Post
    If you are using a double top-plate and can not offset the joints in the two plates by at least 24 inches, you are allowed to splice the top-plate using the 3x6x.0.036 galvanized plate.
    So if you can't stagger, you use the single-plate spec for the top plate. Is this your interpretation, or did you find this somewhere more "official"?

  4. #4
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    Default Re: Top plates - IRC R602.3.2

    Found it in a copy of the IRC that includes explanations on each section.

  5. #5
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    Default Re: Top plates - IRC R602.3.2

    As always, each building inspector can form their own interpretation of the code. I would call my local building inspection office and ask how they would interprete it.

  6. #6
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    Default Re: Top plates - IRC R602.3.2

    Thanks Dave. Inspector wrote I can use the 602.3.2 method. The wall in question has a triple top plate, so I wasn't sure he meant the single top plate spec. Didn't want to wait till Monday to ask.

  7. #7
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    Default Re: Top plates - IRC R602.3.2

    Quote Originally Posted by dgbldr View Post
    Thanks Dave. Inspector wrote I can use the 602.3.2 method. The wall in question has a triple top plate, so I wasn't sure he meant the single top plate spec. Didn't want to wait till Monday to ask.
    I'm not sure what your problem is. Did you stagger the joints less than 24"?
    Last edited by Joe Carola; 04-18-2010 at 06:03 AM.
    Joe Carola

  8. #8
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    Default Re: Top plates - IRC R602.3.2

    Yes Joe, this is a renovation and the triple top plate was rotted in a spot through all 3 layers. Had to replace a section of all 3 layers and could not stagger all the joints more than 24" because of space constraints.

  9. #9
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    St. Paul, MN & Northern WI
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    Default Re: Top plates - IRC R602.3.2

    dgbldr:

    I think DaveR is right on the money, even though he claims not to be writing every bldg. inspector’s opinion on the matter. I might add to what he said: I think they want the bottom or single pl. splice to fall over a stud; and there is probably some correlation btwn. the number of 8d nails on either side of the splice whether you use the galv. stl. pl. or it’s a double top pl. with splices at 24". With the single top pl. you need the 3x6 stl. splice pl. and a similar type 90° tie pl. at corners. Also, with the triple top pl., I suspect that if you could have gotten one of the three splices offset by 24" that would have been O.K. too.

    Some of the reasoning behind this matter is as follows. We want some continuity in the top and bot. wall plates in our wall framing and for shear walls to work properly. We get this continuity in the bot. pl. through the floor diaphragm and the rim joist. At the top pl. we always got this continuity by using the double top pl. with splices staggered at least 24" and this served several functions. The lap at the corners prevented the corner tops from racking wrt each other, and the double top pl. spanned well enough btwn. 16" o/c 2x4 studs to carry trusses at 24" o/c, as long as the loads or span lengths were within reason. As Dave suggests the first reason for 2x6 walls was thicker insul., but then someone got the bright idea that 2x4 studs at 16" o/c and 2x6 studs at 24" o/c have essentially the same column cap’y, so let’s space the studs at 24". But, now the double top pl. was not adequate as a spanning member if the trusses were not essentially centered on the studs. Actually, I think the code allows you to be several inches off center, please verify this, as I don’t have the code in front of me. And finally, since we forced the loading to be near the studs, we didn’t need the double top pl. for bending btwn. studs or for continuity if we used a galv. stl. tie pls. at splices and at corners to provide the needed continuity. The splice pl. dimensions are essentially to provide enough shear strength at the nail heads, and to provide enough edge and end distance on the wood pl. and enough nail spacing to prevent splitting.
    Dick Hackbarth, PE
    RWH&AI, Consulting Engineers

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