This project shows you how to install angled decking boards using a center strip.
If you attempt to install angled decking boards that meet at their miter cuts, expect a struggle. Decking boards may vary in width by as much as 1/4 inch, making it very difficult to maintain perfect joints. If the spacing between boards varies or one board bows slightly, the joint will gap. The project is much more manageable if you install a center strip and butt the miter cuts against it.
This pattern has another advantage: Because you end up with two relatively narrow sections of decking, most of the boards that run between the house and the center strip will be exactly the same size. The boards that run from the center strip to the outside of the deck can be miter-cut on one end only; let the other end run wild, then snap a chalk line, and cut the ends.
About eight hours to cut and install angled decking with a center strip for a 300-square-foot deck
Tape measure, hammer, drill, circular saw, layout square, power mitersaw, chalk line
Making consistently accurate 45-degree miter cuts, fastening with screws or nails
Install framing with two parallel rows of blocking
Decking boards, nails or screws
Temporarily attach a strip of 1/4-inch plywood against the house to act as a spacer. Choose a particularly straight decking board to use as the center strip. Position it midway between the rows of blocking and measure at various points to make sure it is exactly parallel to the house. (If the deck section between the strip and the header is slightly narrower or wider than the section between the strip and the house, that will not be noticeable.) Double-check that the board is straight, and fasten it with two screws or nails driven into each joist.
Miter-cut the end of one board and hold it in position on the deck with one end resting on the center strip. Measure from the corner of the resulting triangle in two directions, as shown above. When the measurements are equal, the board is at 45-degrees to the house. There should be a space of about 1/8 inch between the center strip and decking. Subtract the 1/8 inch when marking the boards or just cut to the good side of the mark instead of the waste side. The saw blade will remove about 1/8 inch.
Place the decking board in position with one end pressed against the plywood spacer at the house and the other end against the center strip. Use nails to space the miter-cut piece slightly away from the center strip. Measure again to see that the board is at a 45-degree angle to the house. Sight down the length of the board to see that it is straight. Fasten it with as many nails or screws as needed to keep the board straight.
For boards on the other side of the center strip, miter cut one end only. Use a layout square to make sure that the first board on this side is directly across from a board on the house side. Check that the board is straight and fasten it with as many fasteners as needed to keep it straight.
Once some full-length pieces are installed, measure for the shorter pieces on the house side; these must have miter cuts on both ends. For each piece, cut one end at a 45-degree miter. Place the board in the position where it will go, with one end pressed against the plywood spacer and nails used as spacers along its length. Mark the board for the miter cut on the other end.
Let the boards on the other side run wild. Once all the boards are installed with as many fasteners as needed to keep them straight, snap a chalk line 1-1/2 inches out from the header joist and cut along the line. Tack a long, straight board as a guide to ensure a straight cut. Once the decking is trimmed, strike a chalk line at each joist and drive the rest of the fasteners. Drill pilot holes before adding fasteners near the ends of boards.