Stairs

Handrails may be continuous or post-to-post (or more accurately ""newel-to-newel""). For continuous handrails on long balconies, there may be multiple newels and tandem caps to cover the newels. At corners, there are quarter-turn caps. For post-to-post systems, the newels project above the handrails.

Other terminology

• balcony - For stairs with an open concept upper floor or landing, the upper floor is functionally a balcony. For a straight flight of stairs, the balcony may be long enough to require multiple newels to support the length of railing. In modern homes, it is common to have hardwood floors on the first floor and carpet on the second. The homeowner should consider using hardwood nosing in place of carpet. Should the carpet be subsequently replaced with hardwood, the balcony balustrade may have to be removed to add the nosing.
• landing or platform - A landing is, structurally, an intermediate floor between flights of stairs. It is typically used to allow stairs to change directions, or to allow the user a rest. As landings consume floor space and are structurally floors, they can be quite expensive to build. However, changing the direction of the stairs allows stairs to fit where they would not otherwise, or provides privacy to the upper level as visitors downstairs cannot simply look up the stairs to the upper level due to the change in direction.
• runner - Carpetting that runs down the middle of the stairs. Runners may be directly stapled or nailed to the stairs, or may be secured by specialized bar that holds the carpet in place where the tread meets the riser.
• spandrel - If there is not another flight of stairs immediately underneath, the triangular space underneath the stairs is called a "spandrel". It is most often used as a closet.
• stairwell - This is the space in the building where the stairs are constructed. This may require special structural design so that the floors around the stairwell do not require structural walls so that the stairs themselves are open to the floors.
• staircase - This term is often reserved for the stairs themselves: the steps, railings and landings; though often it is used interchangeably with "stairs" and "stairway".
• stairway - This term is often reserved for the entire stairwell and staircase in combination; though often it is used interchangeably with "stairs" and "staircase".

Measurements

Stair measurements:

• The rise height of each step is measured from the top of one tread to the next. It is not the physical height of the riser which excludes the thickness of the tread.
• The tread depth or length is measured from the edge of the nosing to the vertical riser. It is sometimes called the going.
• The total run of the stairs is the horizontal distance from the first riser to the last riser. It is not simply the sum of the individual tread lengths due to the nosing overlapping between treads.
• The total rise of the stairs is the height between floors (or landings) that the flight of stairs is spanning.
• The slope of the stairs is the total rise divided by the total run (not the individual riser and treads due to the nosing). It is sometimes called the rake or pitch of the stairs. The pitch line is the imaginary line along the tip of the nosing of the treads.
• Headroom is the height above the nosing of a tread to the ceiling above it.
• Walkline - For curved stairs, the inner radius of the curve may result in very narrow treads. The "walkline" is the imaginary line some distance away from the inner edge on which people are expected to walk. Building code will specify the distance. Building codes will then specify the minimum tread size at the walkline.
• To avoid confusion, the number of steps in a set of stairs is always the number of risers, not the number of treads.

Ergonomics and Building Code Requirements

Ergonomically and for safety reasons, stairs have to have certain measurements in order for people to comfortably use them. Building codes will typically specify certain measurements so that the stairs are not too steep or narrow. Building codes will specify :

• minimum tread length, typically 9 inches including the nosing. Paradoxically, most human feet are longer than 9 inches, thus people's feet don't actually fit on the tread of the step.
• maximum riser height, typically 8.25 inches. Note that by specifying the maximum riser height and minimum tread length, a maximum slope is established. Residential building codes will typically allow for steeper stairs than public building codes.
• Riser-Tread formula: Sometimes the stair parameters will be something like 2 times riser + tread equals 24 inches. Thus a 7 inch rise and a ten inch tread exactly meets this code. If only a 2 inch rise is used then a 20 inch tread is required. This is based on the principle that a low rise is more like walking up an gentle incline and so the natural swing of the leg will be longer. This makes low rise stairs very expensive in terms of the space consumed. Such low rise stairs were built into the Winchester Mystery House to accommodate the infirmities of the owner, Sarah Winchester, before the invention of the elevator. These stairways, called "Easy Risers" consist of five flights wrapped into a multi turn arrangement with a total width equal to more than four times the individual flight width and a depth roughly equal to one flight's run plus this width. The flights have varying numbers of steps.
• variance on riser height and tread depth between steps on the same flight should be very low. Building codes may specify variances as small as 0.25 inches. The reason is that on a continuous flight of stairs, people get use to a regular step and may trip if there is a step that is different, especially at night. The general rule is that all steps on the same flight must be identical. Hence, stair are typically custom made to fit the particular floor to floor height and horizontal space available. Special care must be taken on the first and last risers. Stairs must be supported directly by the subfloor. If thick flooring (e.g. thick hardwood planks) are added on top of the subfloor, it will cover part of the first riser, reducing the effective height of the first step. Likewise at the top step, if the top riser simply reaches the subfloor and thick flooring is added, the last rise at the top may be higher than the last riser. The first and last riser heights of the rough stairs are modified to adjust for the addition of the finished floor.
• maximum nosing protrusion, typically 1.25 inches to prevent people from tripping on the nosing. Another reason for limiting the nosing is that the nosing effectively reduces the tread width of the next lower step.
• height of the handrail. This is typically between 34 and 38 inches, measured to the nose of the tread. The minimum height of the handrail for landings may be different and is typically 36 inches.
• railing diameter. The size has to be comfortable for grasping and is typically between 1.25 inches and 2.675 inches.
• maximum space between the pickets of the handrail. This is typically 4 inches.
• openings (if they exist) between the bottom rail and treads are typically no bigger than 6 inches.
• minimum headroom
• maximum vertical height between floors or landings. This allows people to rest and limits the height of a fall.
• mandate handrails if there is more than a certain number of steps (typically 2 risers)
• minimum width of the stairway, with and without handrails
• not allow doors to swing over steps; the arc of doors must be completely on the landing/floor.

asymmetric steps. A pure spiral assumes a circular stairwell and the steps and handrail are regular and symmetric. A tight spiral stair with a central pole is very space efficient in the use of floor area. A user of these stairs must take care to not step to close to the central pole as it becomes more likely that one or more steps may be missed, especially when going down. One should always take care to continuously use the handrail so that additional support is available in the event that a step is missed. Using the handrail will also direct the user to the safer outer portion of the treads.

Helical or circular stairs do not have a central pole and there is a handrail on both sides. These have the advantage of a more uniform tread width when compared to the spiral staircase. Such stairs may also be built around an eliptical or oval planform.

Both spiral and helical stairs can be characterized by the number of turns that are made. A "quarter-turn" stair deposits the person facing 90 degrees from the starting orientation. Likewise there are half-turn, three-quarters-turn and full-turn stairs. A continuous spiral may make many turns depending on the height. Very tall multi turn spiral staircases are usually found in old stone towers within fortifications, churches and in lighthouses.

Winders may be used in combination with straight stairs to turn the direction of the stairs. This allows for an infinite number of permutations.

Alternating tread stairs

Where there is insufficient space for the full run length of normal stairs, alternating tread stairs may be used. Alternating tread stairs are a recent invention that allows for safe forward-facing descent of very steep stairs. The treads are designed such that they alternate between treads for each foot: one step is wide on the left side; the next step is wide on the right side. There is insufficient space on the narrow portion of the step for the other foot to stand, hence the person must always use the correct foot on the correct step. The slope of alternating tread stairs can be as high as 65 degrees as opposed to standard stairs which are almost always less than 45 degrees. The advantage of alternating tread stairs is that people can descend face forward. The only other alternative in such short spaces would be a ladder which requires backward-facing descent. Clearly alternating tread stairs may not be safe for small children, the elderly or the physically challenged. Building codes typically classify them as ladders and will only allow them were ladders are allowed

Longest Stairway

The longest stairway is listed by Guinness Book of Records as the service stairway for the Niesenbahn funicular railway near Spiez, Switzerland, with 11 674 steps and a height of 1669 metres . The stairs are strictly employee-only.

See also Stairway to Heaven.