How to Build a Walkout Deck

Clear the area in front of the wall where the deck will be installed so there is no debris, furniture or other items on the ground. Mark out the area where the deck will extend with chalk. Remove any paving slabs from inside the marked-out area.

Dig the ground out to a depth of 6 inches by the side of the building; as you go, taper it down to a depth of 8 inches further from the building with a spade. Tamp down the ground with a plate compactor to ensure a firm foundation for the deck.

Measure the height from ground level that you want the deck to stand with a tape measure and add 12 inches to find the length of the support posts. Cut enough 2-by-4 lumber to this length for one support post per corner and an additional post every 12 inches along each side of the deck with a circular saw.

Cut two 2-by-4 timbers to the width of the deck. Cut two 2-by-4s to the length of the deck. Draw 1-by-1 inch squares in one corner of both ends of the 2-inch-wide faces on each length and width piece. Cut these squares out with a jigsaw to leave 1-by-1-by-4 inch notches in the pieces.

Screw the pieces together with the joints interlocked to form a rectangle the size of the deck with a hammer drill and screwdriver drill bit to countersink two 6-inch-long screws per joint. Divide the width of the deck by 12 to determine the number of support joists you need. Cut this many lengths of 2-by-4 timber as long as the length of the deck minus 4 inches.

Attach the support joists to the frame with two countersunk 6-inch-long screws at each end of the joists to securely connect the joists to the frame. Varnish the frame with exterior-grade varnish and a paintbrush. While the varnish is drying, dig a 12-inch-deep hole at the two front corners and every 12 inches along the front side of the deck area with the spade.

Dig a 12-inch-deep hole 2 inches in front of both back corners of the deck area and every 12 inches between the two corners. Dig 12-inch-deep holes every 12 inches down the sides of the deck area between the corner holes. Mix a batch of concrete from one part cement, three parts sand and one part water. Stand the support posts in the holes. Fill the holes with cement.

Wait 48 hours for the cement to set. Hold the deck frame so it is at the top of the support posts, with the top of the frame flush with the top of the posts. Drill two holes through both the frame and each of the posts with the hammer drill. Screw lag bolts through the frame and the posts to fasten the two together securely.

Varnish the support posts. When the varnish is dry, cover the compacted soil with plastic sheets. Pour gravel over the sheets up to ground level. Rake the gravel flat. Place the first decking slat on top of the frame in the back left corner. Screw the decking slat to the frame and the support joist it attaches to with countersunk screws 1 inch longer than the slats are thick.

Place the second decking slat beside the first slat so it is flush with the end of the first slat. Screw this slat down in the same manner. Repeat until the first row of decking is screwed down. Continue screwing down the slats until the surface of the deck is covered. Varnish the decking with exterior-grade varnish. Wait 24 hours for the varnish to dry before using the deck.