To make outdoor concrete steps, use premade stair stringers and lumber boards as the mold into which the concrete is to be poured. Fill the mold tightly with concrete, smooth the surface of each stair, and apply a layer of sealer.
Begin making the outdoor concrete steps by leveling the area where the steps are to stand. To do this, remove the excess soil, and press the area down firmly using the rear side of a shovel to make it more compact.
Then, place the premade stair stringers made of wood at the appropriate position. Cut two-by-eight lumber to the required size so that the boards fit perfectly across the front of all the steps. Screw each board to the stringer with deck screws. Grease the inner side of the stringer using cooking oil. Ensure that the mold stands firmly on the ground.
If desired, shovel gravel inside the mold to reduce the amount of concrete used, and then pour concrete mix. The gravel should fill the mold's core. Alternatively, fill premixed concrete comprising of gravel, cement and sand in the mold. Pack the concrete tightly in the mold so that pockets of air and cracks are eliminated. Also, ensure that the mold is somewhat overfilled.
After filling, smooth the steps using a trowel, and brush the stairs using a broom to create grip. Let the concrete cure for 1 to 2 days. Then, take out the stair mold, and finally apply sealer on the stairs by rolling it using a 1/4-inch nap roller.