How to Build a Deck With 45 Degrees at the Ends

Stand at the starting point of the long side of the deck next to your house. Spray a mark on the ground there with spray paint. Walk the length of the long side of the porch, while staying next to the side of your house, and make a mark on the ground every 6 feet. If the long side needs to be a length that is not evenly divisible by six, then make the marks every 5 feet or even every 4 feet.

Tie a 20-foot length of string to a stake and drive the stake into the ground at the place where you made your first mark. Stretch the string out taut at 45 degrees from the wall of your house; use a protractor to help you do this. Walk along the direction that the string runs and spray a line on the ground as you go. When you are as far from your house as you want the deck to extend, then stop. Drive the stake into the ground at the last mark you made then draw another 45-degree line slanted toward the first mark.

Divide the distance between your house and the proposed front of the deck by six. This is the number of beams you will need. If the distance cannot be evenly divided by six, then add more until it can be evenly divided. Stand on the first mark you made. Walk along the slanted line and make as many evenly spaced marks as there are beams. Do the same for the other slanted line.

Walk across to the other line at every mark and keep parallel to the wall of the house. Make a mark on the ground every 6 feet at the most, just as for the first row of marks.

Dig a post hole at every mark you made. Make it either 1 foot in depth or below the frost line, whichever is deeper. Mix up a batch of concrete. Place one 4-by-4 post into each hole and fill it with at least 6 inches of concrete. Use a level to ensure the post is straight. Once the concrete is dry, fill the rest of the holes with dirt.

Make a mark on each post as far off the ground as you want the bottom of the deck to be. Cut the posts off at these heights.

Cut two 2-by-8 boards to the length of your longest side. Screw them together with 3-inch-long screws to create a beam. Lay the beam onto the row of posts closest to the house. Nail it to the tops of the posts. Put beams on the other rows of posts in the same manner.

Lay 2-by-6 deck boards across the beams. Cut them to length so that they fit evenly on the beams beneath them. Screw them to the beams underneath with two screws for each beam.

Stain and varnish the deck. Allow it to fully dry before walking on it.