The straight run stairs are the stairs used most in new home construction. Straight stairs, as the name implies, have no turns. These stairs are not as costly to construct as other types of stairs.
The L stairs has one landing at some point along the flight of steps. If the landing is near the top or bottom of the stairs, the term Long L is used to describe the difference. L stairs are most commonly used when the space required for a straight run stairs is not available.
Double “L” Stair
Double L stairs require two 90 degree turns along the flight. They may be used when space is not available for either the straight stairs or the L stairs. Double L stairs are not most frequently used in a residential construction.
U Stairs may be constructed may be either as wide U or narrow U stairs. Both have two flights of steps parallel to each other with a landing between. The difference between wide and narrow U stairs is the space between the two flights. Narrow U stairs have little or no space between the flights while U stairs have a well hole between.
Winder stairs have “pie-shaped” steps which are substituted for a landing. This type is used when the space is not sufficient for the L stairs. If winder stairs are used, the width of the triangular steps should be sufficient at midpoint to provide a tread width equal to the regular steps.
The shape follows a constant radius or arc of a circle.
Spiral or circular stairs are gaining in popularity and the components are now manufactured by several companies. They may be used where little space is available. Most spiral stairs are made from steel and welded together, however, it is possible to construct them from wood.