How to Concrete a Trench

Remove any debris or organic material inside the trench. If there is grass or other plants in the trench, it must be dug out.

Lay a yardstick along each side of the trench and make note of the areas that stick out past the yardstick. Level the sides of the trench that stick out by digging out the uneven parts with a shovel.

Level the bottom of the trench with a tamper. You may need to place loose soil in the bottom of the trench to make this process easier.

Measure the dimensions of the trench with the yardstick or with a measuring tape.

Cut a pieces of straight lumber that corresponds to the length and depth of each side of the trench. Use a circular saw to cut the lumber, or use a hand saw if the lumber you are using isn't very wide.

Nail the lumber together at the corners to form a rectangular shape that fits against the sides of the trench. This structure doesn't need to be terribly sturdy, and the lumber doesn't need to be the best quality. This structure will be used only temporarily while the cement is curing. To make this easy for you, assemble the structure outside the trench, then ask a friend to help you lower the structure into the trench.

Mix the concrete according to the manufacturer's instructions. Use a concrete mixer drill attachment to mix the concrete thoroughly and evenly. Wear protective gloves when working with concrete, and wear a face mask when mixing it. Do not let wet concrete touch your skin.

Fill the structure in the trench halfway with concrete. If you'll be building something heavy on top of the concrete, like a stone or brick structure, lay rebar in a grid form into the concrete, then fill the rest of the structure with concrete.

Level the top of the concrete by with a 2-by-4 piece of lumber, a trowel or a squeegee.

Allow the concrete time to cure according to the manufacturer's instructions.

Wash off the surface of the concrete with a garden hose, then clean the concrete with a stiff brush, to get rid of any dust.

Pry off the wooden structure around the concrete with a pry bar. Fill in the space between the edge of the concrete and the trench with loose soil, and pack it down.