Steps leading up to the porch are built like a small staircase with some subtle differences to adapt to use outside in the elements. Porch steps have deeper treads and shorter risers than indoor steps to prevent slipping on wet stairs in inclement weather. Indoor stairs are built in place, but porch steps are usually small enough to be pieced together before finally attaching them to the porch and anchoring the base to the ground.
Improperly supported steps can crack and break with movement of the soil from freezing or flooding. A solid foundation to attach the posts supporting the ends of the porch steps can help to prevent this up and down movement. To keep the steps from shifting sideways with use, stringers or walls need to be built to add strength to the steps.
Stringers are wooden boards nailed to each of the steps on the sides. Used in both indoor and outdoor stairs, the stringer extends from the ground to the top of the steps. If you are using wood stringers for porch steps, select pressure-treated wood, which is more weather resistant than untreated wood. The stringer can retain the straight sides of the board or cut to follow the shape of the risers and treads on the steps. If you install a handrail on the steps, it can be attached to the stringer on either side of the steps.
For a permanent fixture to strengthen wood steps leading to the porch, construct masonry walls on either side of the steps. These serve both as supports for the sides of the steps and as retaining walls to keep raised soils around the stairs out of the walkway. Use this option if you build wooden steps with earth support under the steps. The wall will act to keep the soil under the steps, where it strengthens the stair structure.