I am buying a older home, the back porch steps are concrete and the top step that is just below the porch is extremely low is there a way to add a half step to avoid stepping down so long a distance?
One solution, if you have some space to work with at the foot of the concrete steps, is to add some new steps constructed with pressure treated lumber. Here is an example to convey the idea.
The unevenly spaced original steps are replaced with a new set that are evenly spaced from the ground level up to the top. In this example I show the use of 2x12 lumber to create both the steps and the stringers under the steps. You could place the stingers to the outside edges of the existing concrete structure or notch them as necessary to fit over the nose of the existing concrete steps.
Not shown in this concept drawing is a header that would be secured between the top ends of the stringers under the new step. The header would be flat against the riser of the existing top step. Fasteners through this into the existing concrete would secure the new timber structure.
Another advantage of this concept is that many old style steps do not have adequate landing area at the top to make it easy to negotiate opening a outward swinging screen/storm door. The added width of the top step can help with this problem.