How to Cut Step Risers
Stairs consist of three parts: the stringers, the risers and the treads. The treads are the actual step; the risers act as a backstop on the rear of the treads; and the stringers provide the structure that supports the treads and risers.
Risers are normally cut after the stringers have been fabricated and nailed in place, but are usually installed before the stair treads. Risers have a height equal to the distance between the tops of two adjacent treads. The width of the risers depends upon their finish. If the eventual finish is to be carpet, the risers are cut one inch shorter than the wall to wall measurement of the stairwell; this allows the carpet-layer to wrap the carpet into the resulting half inch gap at each wall. If the risers will be left exposed, they are cut tight to the stairwell walls.