Stair construction is complex compared with many other carpentry tasks. Straight staircases are the easiest to design and build, but they require a surprising amount of space. In small structures, such as cabins, a straight staircase might prove totally impractical. If this is the case, you need to consider a compact L-shaped or U-shaped staircase design.
Understand Stair Terminology
A stairway design is defined primarily by unit rise, unit run, number of steps and headroom. The unit rise is the vertical distance covered by each step, and the unit run is the horizontal distance covered by each step. The vertical surface of a step is called the riser, so unit rise is also referred to as riser height. Similarly, unit run is also known as tread width, because the horizontal surface of a step is called the tread. The head room is the available vertical distance above any tread; this dimension is limited by the bottom of the upper floor or possibly by a ceiling if the stairway is going into an attic or knee-wall second story.
Consider Your Floor Space
Your local building codes will determine the detailed dimensions required for your staircase, but most codes reflect a set of generally accepted specifications. The unit rise must be no greater than 8 inches, and the unit run must be at least 9 inches. If a straight staircase with a 10-inch unit run and an 8-inch unit rise covers 8 vertical feet, the total run would be 10 feet. A typical step width is 36 inches, so this staircase will occupy 30 square feet of floor space. More importantly, with a straight staircase in a small cabin, this obstructed floor space might cut right through prime living area. The solution is to design a staircase that changes directions part way up the stairs.
Make Your Staircase Fit
A non-straight staircase is more appropriate for cabins because it can be more effectively arranged to minimize the amount of obstructed floor space. In some cabins with a knee-wall second story, it might be almost impossible to use a straight staircase -- the top steps will be close to the side of the building where the headroom on the second floor is only three of four feet. An L-shaped staircase, which incorporates a 90 degree turn, will fit nicely in an out-of-the-way corner of your cabin. A U-shaped staircase, which begins in one direction then turns around and continues ascending in the opposite direction, will not cut through the middle of your living area when placed along a wall.
Know Your Winders and Landings
An L-shaped or U-shaped design requires special steps that allow the staircase to safely change directions. Your two options are a landing, which is simply a platform between two staircase sections, or winders, which are steps that have irregular shapes because they wind around the change in direction. Use a landing whenever possible -- they are safer and simpler to construct. Each dimension of the landing must be the same as the width of the staircase. Winders should be supported by a sturdy landing, and all the winder steps must have consistent dimensions. Winders are difficult to design and build; avoid them unless your cabin is so small that even a staircase with a landing will not quite fit.
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