How to Build an Outdoor Concrete Bench

Cut a piece of 3/4-inch thick particle board to measure 15-by-20 inches. This is the base for a leg form.

Cut out two lengths of 1-by-6 inch particle board to measure 15-inches long. These are the short sides of the leg form. Cut two more lengths of 1-by-6 inch lumber to measure 20 inches long. These are the long sides for the form. Arrange the four pieces to create a rectangle. Screw the rectangle together, then screw the base onto the rectangle. Repeat steps 1 and 2 to make a second leg form.

Cut a second piece of 3/4-inch particle board into a rectangle that is 15 inches long and 5 five feet wide. This is the seat base form.

Cut two lengths of 1-by-4 inch particle board to measuring 5 feet. These will be the sides of the form used for the seat. Cut two short sides from 1-by-4 inch particle board to measure 15-inches long. Arrange and screw the four pieces together in a rectangle. Screw the base on to the top of the rectangle.

Place all three forms on a flat surface, base down. Spread vegetable oil on the inside base and sides of the forms.

Mix a batch of concrete following the package instructions. Mix the concrete one bag at a time as you need more.

Fill the molds with the mixed concrete. Stop pouring into the molds when the concrete is even with the top of the sides of the form. Use a scrap piece of lumber to smooth out the wet concrete. Allow the concrete to dry for 3-7 days before handling.

Ask an assistant to help you flip the molds over. Gently knock the seat and legs out from their forms.

Select a level location to install your new bench. Place the two legs vertical to the ground in the selected location. Arrange the legs parallel with each other and exactly 4 feet apart. Mix a small batch of concrete and spread over the top of the legs. Gently set the bench seat across the two legs.

Use sandpaper to sand down any rough spots on the bench. Pay particular attention to corners and edges of the seat.