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plywood clips


John Dirks Jr
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I thought they were used for keeping the edges of sheathing aligned in between the rafters. Take a 24"OC rafter setup for instance. Without clips the sheathing can warp and bypass the sheet next to it and cause stress to the shingles.

This is what was mentioned in other sources I have anyway. This is why I asked since I havnt seen any recommendations of when they should be used. I was not under the impression that they held any structural strength.

I mentioned the different materials in relation to thier stand alone strength. For instance, stronger materials spanning shorter distances would be less likely to need the aid of clips to keep the edges aligned.

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The H clips provide edge support for the plywood sheathing between the rafters. For a given sheathing thickness, they can allow greater spacing between the rafters. For a given rafter spacing, they can allow thinner sheathing to be used. Whether or not edge support is needed depends upon what rafter spacing and sheathing thicknesss is present. The H clips are not the only way of providing edge support. Solid wood blocking is another way it could be done. Using tongue-and-groove plywood is another. The clips are also designed to provide a secondary benefit -- space the panels -- but that is not their primary purpose (unless they are installed when edge support is not needed).

If you have a copy of the IRC go to §R503.2 Wood structural panel sheathing. Then check out TABLE R503.2.1.1(1) ALLOWABLE SPANS AND LOADS FOR WOOD STRUCTURAL PANELS FOR ROOF AND SUBFLOOR SHEATHING AND COMBINATION SUBFLOOR UNDERLAYMENT. In that table you'll find two columns under the MAXIMUM SPAN heading: "With edge support" and "Without edge support". The span heading references a footnote d. Footnote d says: "d. Lumber blocking, panel edge clips (one midway between each support, except two equally spaced between supports when span is 48 inches), tongue-and-groove panel edges."

TECO has a fact sheet on the clips:

http://www.tecotested.com/documents/200 ... HClips.pdf

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In addition to what Brandon posted, they're also needed at the edges of the narrow panels that often end up near the ridge.

If the plywood is ripped down to between 16" & 24", H-clips or blocking should be used. 12"-16" requires blocking only. <12", both edges need blocking.

From the dips that I see, near the ridges of lotsa McMansions, edge support isn't being regularly installed.

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