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Community and Q&A

Hurricane ties and sealing top plate

Kevin Camfield | Posted in Green Building Techniques on

Does anyone have a good technique for sealing the ceiling plane air barrier to the top plate when using scissor trusses and hurricane ties? We will have a sloped ceiling with a 2.5/12 pitch and a vented roof assembly.

One of my questions is how to get a good seal around the all of the hurricane ties without a lot of fuss. The most commonly used tie here is the Simpson H1 tie. Some here have suggested using the truss screws instead, but the lateral strength is a lot lower. We are a high wind and earthquake zone near Seattle.

I’m sure others have dealt with this and perhaps it is as simple as using more sealant or thicker gasket but I thought I’d check to see if there was a more elegant approach. It seems like some sort of flashing or backing at that joint would help a lot to give something more substantial to seal to, hurricane ties not withstanding.

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Replies

  1. Expert Member
    Malcolm Taylor | | #1

    Kevin,

    I don't know if the raised-heel on your trusses necessitates structural blocking or not (It is commonly called out in high seismic areas). If they do then the concerns about lateral strength are taken care of. If not, I'd still consider truss-screws, and block between the trusses with 2"x4"s to achieve the lateral shear.

  2. Kevin Camfield | | #2

    Malcolm,
    Thanks for the reply. I will have blocking between the trusses. Unfortunately the raised heel is pretty short. We have ~8" with a 2x6 top cord and exposed tails. The truss company was suggesting full height vented blocking. I'm assuming that to get the lateral shear strength, the blocking needs to be secured to the top plate. Is that correct? A lot of times here the blocking is cut to run perpendicular to the roof deck meeting the top plate at and angle and not nailed there.

    I can get blocks with a beveled top so that they sit vertical in the space between the trusses. I could block between the trusses with 2x4's on the flat and use a shorter vented block but I was trying to save as much room as possible in the heel area for the spray foam. If I use a full height vented block and run the sheathing to the bottom of the top cord, nailing into the block, does that provide similar lateral strength? I guess one could also toenail the block from the inside if splitting of the block is not a problem. Do any one of those sound better to you than the others? I would like to use the truss screws.

  3. John Semmelhack | | #3

    What material are you using for the air barrier at the ceiling?

  4. T Carlson | | #4

    Im not in high wind, but have put H1's on the exterior with no crying from building inspectors. You could gasket the top plate prior to drywall or seal after the ceiling is hung before the walls are hung.

    Any vault is difficult to air seal.

  5. Expert Member
    Malcolm Taylor | | #5

    Kevin,

    If structural blocking is required, the particulars get called out by either the truss manufacturer or an engineer. There usually isn't much choice in how you do it.

    I was suggesting a 22 1/2" 2"x4" (on the flat) block nailed to the top plate as lateral re-enforcement to give the truss-screws a similar strength to the clips. Sounds like you may need more than that.

  6. Kevin Camfield | | #6

    John,

    I was planning to use either drywall or use OSB nailed to the trusses to build an electrical chase by furring down from that for the drywall. If I just use the drywall, it seems like the drywall to top plate seal wouldn't be all that robust. The OSB electrical chase just seems expensive.

    Kevin

  7. Kevin Camfield | | #7

    T. Carlson,

    I never thought about putting the hurricane clips on the exterior. That sounds like a good idea. I will be using a rain screen and exposed truss tails. I think that will work since the clips will be back on the sheathing behind the siding. The only complication might be corrosion. We are 30 feet from a salt water bay. I'll look into it.

  8. Kevin Camfield | | #8

    Malcomb,

    What you describe might be the simplest solution. It's clear to me from this thread that I'm going to have to mock something up at least on paper. The rain screen complicates the geometry up there. I'm having a hard time picturing it all. Thanks for the input.

  9. John Semmelhack | | #9

    Kevin - do it once, do it right. Use OSB or plywood and furr down the drywall. Use a fluid applied sealant for the joint. Duralink 50, Prosoco Fast Flash or Joint Filler, Zip Liquid Flash are all excellent...Duralink is the least expensive.

    It's no big deal to spread a bunch of sealant over the clips.

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