Since they spend virtually all of their life exposed to the elements, wooden garden benches only last a few years. However, this is an idea for a garden bench that's virtually impervious to weather and will last much longer. It's solid, easy to build, and makes an attractive addition to any garden. Here's how you can build your own garden bench to last a lifetime.
Step 1 - Build a Form
Start by building a cement form using the sheet of plywood. Cut two 3" pieces from the long side of the plywood then cut two 3" pieces from the short side as well. These pieces will make up the sides of your concrete form. Finally cut the remaining plywood to the size you want for the seating area of your bench.
Build the concrete form by screwing the 3" pieces to the edge of the plywood sheet using drywall screws spaced about every 5 or 6 inches. Install screws where the corners come together to firm them up and ensure the form is strong enough to hold the weight of the concrete.
Step 2 - Level It
Place the form on a relatively level piece of ground. Use your level to make sure it really is level and if not, use shims to level it. This step is important because the concrete in the form needs to be level to ensure your entire bench seat will be the same thickness.
Step 3 - Spray the Form
Next, spray the inside of the form with cooking oil (to ensure the concrete won't stick to the form), then mix your concrete following the instructions on the bag, and carefully pour it into the form. You want to fill the form to about 1/2" from the top.
Gently tap the sides of the form to settle the concrete, then leave it to set up for a couple of days. After the concrete has dried, release it from the form by backing out the drywall screws and removing the sides.
Step 4 - Build Legs
Cut the cedar post into five pieces. One piece 35" long to form the crosspiece that runs under the seat and four pieces each 15" long to form the legs.
Step 5 - Assemble
Assemble the base by measuring and marking the location of the carriage bolts near the top of the legs, and at the end of the crosspiece. At each end, drill a 1/2" hole through the legs and crosspiece and counter sink for the carriage bolt heads and nuts.
Finish the leg assembly by applying wood glue to the meeting edges, then attach the legs to the cross piece using a 10" carriage bolt at each end.
Finally, place your leg assembly where you can enjoy your garden and position the concrete/seat on top. That's it, a garden bench built to last a lifetime.
Step 6 - Maintain the Bench
You could apply a few coats of concrete sealer to help protect the concrete from chipping over the years.
If you leave the cedar unfinished it will weather to a light gray or silver color over time, or you can apply a clear cedar stain to keep it looking fresh.