DO THIS, NOT THAT
Installing porch steps.
Restoring a porch? It’s easy to find deck components at the home center, and it would seem that stair-steps can be constructed by simply nailing 2x lumber to pre-cut sawtooth supports called stringers. For a rear deck, that may be fine. But older houses are often graced with more formal stairs leading to the porch and to the main entry. Before you lay out and cut replacement stringers, call your local code official to get the current specs on tread widths (wide treads require a center carriage) and allowable riser heights. In many cases the original measurements will be fine, but be aware you may need some redesign to meet code. The assembly of treads and risers is critical for durability. Choose woods rated for outdoor exposure (i.e., rot-resistant), and pre-prime all of the components before assembly.
WRONG WAY MOVING TO OPEN RISER
Use proper joinery: just nailing risers onto, above, or behind the tread will allow water to collect in crevices, where it eventually will cause rotting. And avoid the modern urge to eliminate the solid riser. Risers are important to the aesthetic of the stairs. In addition, the risers provide strength and rigidity to the entire assembly.
RIGHT WAY GOOD JOINERY
The best technique for installing treads and risers is to cut them so that they interlock. If you’re familiar with the use of a router, a table saw, or even a rabbet plane, you can make a good joint. The riser is made to fit into a groove on the underside of the tread, while the tread is made to fit into a groove cut into the lower edge of the riser. This interlock makes the assembly quite stiff and keeps rain out of the joints.