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4×8 Sheathing on 9′ wall

climb_on | Posted in General Questions on

We are in Minnesota (Zone 6a). 2200 sq/ft single level (9′ walls), slab on grade.

I was planning on doing 4 x 9 sheets of plywood on the exterior of my double stud wall. The 9′ sheets are about double the price of 4 x 8 sheets. What is the best strategy for applying 4 x 8 sheets on a 9′ wall? Staggered horizontally? Lot of extra seams to tape…and is it counter productive to even consider 4 x 8’s if I have those extra seam that aren’t backed by a stud. I REALLY don’t want to pay $35 a sheet for 4 x 9 cdx.

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  1. user-6811621 | | #1

    what kind of roof system are you using? If you are using energy-heel trusses, you'll be sheathing higher than your wall height. IF you can get the heel height correct, you won't have much plywood waste and a stronger connection between truss and wall.

  2. climb_on | | #2

    Thank you Brian. Yes I am using energy heel trusses and now that I look closer 9' would not even cover it anyway. I'm closer to 10'. Still curious about application strategy.

  3. user-6811621 | | #3

    I am not a pro builder, so hopefully others join in this. I am also in Zone 6 (Montana) and building slab on grade with double stud wall and exterior plywood, so I am anxious to hear other comments as well. If your overall height is 10', one idea would be to run a 2' wide section horizontally along the bottom and an 8' section vertical above it to the top of truss. This would give the maximum strength in the wall-truss connection and minimize the amount of exposed seams. Since you are in snow country, the bottom 2' could be pressure treated plywood to ensure no rotting from drifting snow. Matt Risinger does this in his homes in Austin (check his OSB vs Plywood vid on Youtube), because of the amount of splashing water. Codes vary, but many require blocking between studs in areas where plywood seams would be, or 2' above the sill plate in my example.

  4. user-6184358 | | #4

    If you apply the sheets horizontally you can use thinner shear panel with the same shear value as the thicker sheets.( make sure you know the thickness of backing you siding needs) Look at the foot notes in the shear tables. Perhaps this help make up the cost of the additional blocking needed at the horizontal panel joints. This would require 3 rows of horizontal blocking.
    If you install them vertically then with one row of blocking you can cover the full 10' height.
    Staggering the joints is not needed on shearwalls. It is typically needed on a roof diaphragm.

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