The simplest form is the straight flight of stairs, with neither winders nor landings. These types of stairs were commonly used in traditional homes as they are relatively easy to build and only need to be connected at the top and bottom; however, many modern properties may not choose straight flights of stairs because
Straight stairs can have a mid-landing incorporated, but it’s probably more common to see stairs that use a landing or winder to produce a bend in the stairs as a straight flight with a mid-landing will require a lot of linear space and is more commonly found in commercial buildings. “L” shaped stairways have one landing and usually change in direction by 90 degrees. “U” shaped stairs may employ a single wider landing for a change in direction of 180 degrees, or 2 landings for two changes in direction of 90 degrees each. A Z-shaped staircase incorporates two parallel 90° turns, creating a shape similar to that of the letter ‘Z’ if seen from above.
The wider the spiral, the more steps can be accommodated per spiral. Therefore, if the spiral is large in diameter, via having a central support column that is strong (invariably large in diameter) and a special handrail that helps to distribute the load, each step may be longer and therefore the rise between each step may be smaller (equal to that of regular steps). Otherwise, the circumference of the circle at the walk line will be so small that it will be impossible to maintain a normal tread depth and a normal rise height without compromising headroom before reaching the upper floor.
An example of perimeter support is the Vatican stairwell shown in the next section or the gothic stairwell shown to the left. That stairwell is only tight because of its design in which the diameter must be small. Many spirals, however, have sufficient width for normal size treads (8 inches) by being supported by any combination of a center pole, perimeter supports attaching to or beneath the treads, and a helical handrail. In this manner, the treads may be wide enough to accommodate low rises.
