How to Do Exterior Concrete Flooring in the Backyard

Set out the location of the concrete flooring by spraying the perimeter of the flooring onto the ground with landscape spray. For best results, plot out the size and shape of the flooring beforehand, especially when creating anything bearing curves. Add 2 inches to the perimeter of your design to allow room for the creation of concrete forms.

Excavate a 6-inch-deep hole from the marked area with a spade. Keep the bottom of the excavation level, except for a slight slope away from any structures, dropping 1 inch for every 10 feet of flooring width. Compact the soil at the bottom with a plate compactor to keep shifting after concrete placement to a minimum.

Create a concrete form around the perimeter of the hole using 1-by-6-inch boards and wooden stakes. Line the edge of the hole with the stakes, driving them about 2 inches into the ground with a hammer. Place the boards against the stakes so that they level out with one another at 6 inches in height, the height of the hole. Check for level as you build the forms with a carpenter's level. Attach the boards to the stakes using an electric screwdriver with wood screws going from stake to form. For curved sections, bend the boards slightly to curve them as they meet the stakes surrounding the curved area.

Determine the volume of the hole by multiplying the width by the length and then multiplying the result by the height. Purchase enough concrete mix to cover this volume plus 10 percent, and enough rebar to position a bar every 2 feet along the length and width of the hole to create a supportive grid. You'll also need concrete blocks 2 inches square as rebar supports, enough for a single block every 5 feet. Compute the volume of gravel needed for a 2-inch layer and purchase an extra 10 percent as well. Make certain you have the home improvement shop cut the rebar to fit your flooring length and width at the store.

Fill the base of the hole with gravel in a 2-inch-thick layer. Use a rake to level out the gravel so that it follows the established slope. Compact the gravel with the plate compactor for a strong surface to support the concrete.

Line the bottom of the excavation with the 2-inch concrete stones, one every 5 feet, to hold the rebar grid in position centered in the flooring.

Create the rebar grid. Place the length-sized rebar into the hole, spaced 2 feet apart, then place the width pieces above them, also spaced 2 feet, creating a grid of squares. Place a wire rebar connector around the two layers of rebar wherever they cross, twisting the connector tightly to prevent the rebar from shifting.

Pour the concrete mix into a concrete mixer. You can rent a mixer from a home improvement store or from an equipment rental shop. Add water to the mix, as well as any dye desired to add color to the floor. Mix in the water until you have a smooth and pourable substance. Pour the first spreadable batch into a wheelbarrow and then push the wheelbarrow to the excavation.

Use the spade to fill the form with the concrete. You'll want to fill the form to the top, allowing the level of the form to determine the height of the flooring. Make multiple trips with the wheelbarrow, if needed, until you've filled the form completely.

Drag a screed across the surface of the form and the concrete. Saw the screed back and forth as you drag it across, lowering high points in the concrete while at the same time using the excess concrete from the high spots to fill any voids. This will level out the concrete flooring at the desired height. Run a bull float across the surface after you screed to distribute any aggregate in the concrete evenly throughout its depth. This also pulls a bit of moisture to the top of the concrete, keeping the surface from drying out too quickly.

Wait a few minutes for the flooring to reabsorb the moisture into the slab. Test the slab for firmness using your thumb lightly pressed into the concrete then pulled away. If the imprint of your thumb is a shallow one that doesn't begin filling in with concrete, then you can finish the slab.

Edge the flooring with an edging tool to create a neat border between the slab and the rest of the backyard. Place the edger tool between the slab and the form, with the top of the tool lightly pressing against the concrete top. Pull the tool around the edge of the slab completely, rounding off the edge of the slab to match the angle on the inside edge of the tool. Remove the tool.

Use a straightedge as a guide to cut expansion joints throughout the flooring. Cut a joint every 10 feet with the edge of a trowel, descending into the slab 1/2 inch. Run the bull float across the slab a second time to add water to prevent the new cuts from developing cracks as they cure.

Texture the slab at this time if you wish. Apply any texture desired, or go with a basic nonslip broom texture by brushing a stiff-bristled broom across the slab. You can also stamp desired patterns into the slab at this time as well by spraying the slab with a mold release agent and pressing a series of concrete molds onto the slab surface, imprinting their designs.

Allow the slab to cure for 10 days and then unscrew the stakes from the forms. Pull the stakes from the ground, then pull the forms from the concrete sides and lift from the concrete edge. Fill in the gap between concrete and backyard with filler dirt or with a gravel or border filler of your choice.

Spray the surface of the concrete with a concrete sealant to keep the material from staining. Use a gloss sealant to create a wet, shiny look. Wait 48 hours for the sealant to dry before using the flooring.