How to Install Plywood on a Slope Deck

While plywood isn’t always the first choice when it comes to deck planking, as long as you use 3/4-inch, exterior-grade, pressure-treated plywood, you can install it on your deck. The same rules apply as with any other plywood installation, and all you need are some basic carpentry tools and knowledge. When installing plywood on a sloped deck, the principles are the same as any other type of deck. However, you will want to start on the bottom end of the slope so that you can stack the higher pieces against the lower and allow gravity to help you.

Safety glasses
Work gloves
Tape measure
Pencil
Chalk line
Circular saw
Drill
1 1/2-inch wood screws

Instructions

- 1
  Pick a corner on the lowest section of the deck’s sloped area to start the project. Measure from the outside edge across the floor joists and check that measurement against the length of a piece of plywood. If a piece extends beyond a floor joist, it has to be cut off halfway across the joist so that the next piece in the row can also use that same joist for the edge.
- 2
  Mark a piece of plywood on either side of the cut. For example, if you need to cut a piece of plywood to a length of 45 inches on a 48-inch sheet, make a mark at the top of the piece, then another mark on the bottom edge of the piece.
- 3
  Snap a chalk line between the two marks.
- 4
  Set the depth of the circular saw to 3/4 inch and cut the piece along the mark.
- 5
  Slide the piece of plywood in place on top of the floor joists.
- 6
  Screw it down onto the joists, keeping the screws roughly 3/4 inches away from the edges. Angle the screws in slightly where you straddle a joist with another piece. Keep at least 1/8-inch gap between all pieces to allow for seasonal swelling with heat as well as moisture swelling.
- 7
  Repeat the cutting, mounting and drilling process for all your plywood sheets.

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