Build the Frame
Select an area near the pool or patio that has a level and solid foundation made of either concrete or brick. You may have to build this foundation first. Measure the space to make certain it can accommodate an area 2 feet deep and 40 inches high. Determine how long you can make the bar.
Build a skeleton for the bar out of 2-by-4s. Start with the front, or customer side. Cut two 2-by-4s to your desired length. Cut two more pieces 39 inches long for each end. Cut additional 2-by-4 pieces and space them every 16 inches apart between the long top and bottom pieces. Use carpenter's glue and wood screws to piece this unit together. Screw an additional 2-by-4 across the middle of the back side of this unit for extra durability.
Build two sides for the bar that are 39 inches high by 17 inches wide, with a brace in the middle. Glue and screw together.
Build the bartender's side by placing a 2-by-4 on the floor, the same length as the front piece. Make two side uprights 39 inches high. Space out along the long board three 2-by-4s that are 21 inches in height. Cut a length of 2-by-4 to fit between the two uprights, and screw it on top of the 21-inch uprights. Glue and screw this piece together.
Assemble these pieces together by putting the side pieces between the front and the bartender sides. Glue and screw these pieces together.
Finish the Bar
Add an outer skin to the bar on the customer side. This can be either a weather-resistant treated wood, a wood with a shellac finish or even metal. Attach with wood screws or rivets.
Lay down a plywood bottom layer of the bar top. Cut out the corners so it rests inside the skeleton bar frame and is supported by 2-by-4s on all sides. Screw this piece into place.
Finish off the bartender side of the bar, using plywood that has been sealed with a water sealer. Cover the top of the bar side to create a ledge for storage.
Add a counter top of your choice, overhanging it on all sides by at least 6 inches. Affix to the plywood bottom counter with the manufacturer's suggested adhesive and clamp into place.
Finish the bar by adding a drink rail to the edge of the counter and caulk around the seam to seal it.