Stairway

Stairs, staircase, stairway, flight of stairs are all names for a construction to bridge a vertical distance by dividing it into small ones, steps.

Table of contents

1 Usage 2 Components and terminology 2.1 Step 2.2 The railing system 2.3 Other terminology 3 Measurements 4 Ergonomics and Building Code Requirements 5 Forms 5.4 Alternating tread stairs 6 Longest Stairway

Usage

They are in buildings and used for smaller vertical distances, and as physical exercise, and in the case of emergencies (some stairways, especially on the outside of a building, are only for emergencies, as fire-escape). Stairways may be straight or round, or sometimes consisting of two straight pieces with a corner.

Sometimes there are stairs on a hiking path, avoiding more difficult climbing and also the detour that vehicles have to take.

Stairways are also used to enter and leave some vehicles. They may be a separate object or part of the vehicle, either fixed or foldable/retractable. There are also stairways in double-decker vehicles, and small ones in vehicles with a floor that is not everywhere at the same level.

Stairs are not suitable for wheelchairs and other vehicles. A stairlift is a mechanical device for lifting people and wheelchairs up and down stairs. For sufficiently wide stairs, a rail is mounted to the treads of the stairs. A chair or lifting platform is attached to the rail. A person on the chair or platform is lifted as the chair or plaform moves along the rail. Specialized rails are required for circular stairs or for change in stair directions on a landing. Wheelchairs may require special attachments and wider stairs.

Special stairways are an escalator and a ladder.

Alternatives are an elevator and an inclined moving sidewalk.

In larger and older houses, in addition to the main stairs there may be service stairs. The main stairs would be ornate, and usually opening onto the main foyer. Guests and the home owners would use the main stairs. Household staff would use the service stairs in the back of the house. Service stairs are usually enclosed and utilitarian. They are often steeper than the main stairs. Building code restrictions on the main stairs may not apply to the service stairs. Stairs to attic or basement may also be classified as service stairs for building code purposes.

Components and terminology

Step

The step is composed of the tread and riser.

• tread - The part of the step that is stepped on. It is constructed to the same specifications (thickness) as any other flooring. The tread "length" is measured from the outer edge of the step to the vertical "riser" between steps.
• riser - The vertical portion of the step between steps. This may be missing for an "open" stair effect.
• nosing - An edge part of the tread that protrudes from the riser beneath. If it is present, this means that horizontally, the total "run" length of the stairs is not simply the sum of the tread lengths, the treads actually overlap each other slightly
• bullnose - Where stairs are open on one or both sides, the first step above the lower floor may be wider than the other steps and rounded. The rounded portion of the step is called a "bullnose". The pickets typically form a semi-circle around the circumference of the bullnose and the handrail has a horizontal spiral called a "volute". Besides the cosmetic appeal, bow noses allow the pickets to form a wider, more stable base for the end of the handrail. Handrails that simply end at a post at the foot of the stairs are usually unstable, even with a thick post. A double bullnose can be used when both sides of the stairs are open.
• winders - Winders are steps that are narrower on one side than the other. They are used to change the direction of the stairs without landings. A series of winders form a circular or spiral stairway.
• stringer or sometimes just string - The structural member that supports the treads. There are typically two stringers, one on either side of the stairs; though the treads may be supported many other ways. The stringers are notched so that the risers and treads fit into them. Stringers on open sided stairs are often open themselves so that the treads are visible from the side. Such stringers are called "cut" stringers. Stringers on a closed side of the stairs are closed, with the support for the treads routed into the stringer.
• trim - Trim (e.g. quarter-round or baseboard trim) is normally applied where walls meet floors. Within a flight of stairs there is no trim as the trim thickness will significantly eat into the tread length. Shoe moulding may be used between the lower floor and the first riser. Trimming a bullnose is a special challenge as the last riser above the lower floor is rounded. Today, special flexible, plastic trim is available for this purpose. Scotia is concave moulding that is underneath the nosing between the riser and the tread above it.

The railing system

The balustrade is the complete system of railings and pickets that prevents people from falling over the edge:

• banister, railing or handrail - The angled member for handholding, as distinguished from the vertical pickets which hold it up for stairs that are open on one side; there is often a railing on both sides, sometimes only on one side or not at all, on wide staircases there is sometimes also one in the middle, or even more. The term "banister" is sometimes used to mean just the handrail, or sometimes the handrail and the balusters or sometimes just the balusters[1].
  • volute - A handrail for the bullnose step that is shaped like a spiral. Volutes may be right or lefthanded depending on which side of the stairs they occur when facing up the stairs.
  • turnout - Instead of a complete spiral volute, a turnout is a quarter-turn rounded end to the handrail.
  • gooseneck - The vertical handrail that joins a sloped handrail to a higher handrail on the balcony or landing is a gooseneck.
  • rosette - Where the handrail ends in the wall and a half-newel is not used, it may be trimmed by a rosette.
  • easings - Wall handrails are mounted directly onto the wall with wall brackets. At the bottom of the stairs such railings flare to a horizontal railing and this horizontal portion is called a "starting easing". At the top of the stairs, the horizontal portion of the railing is called a "over easing".
  • core rail - Wood handrails often have a metal core to provide extra strength and stiffness, especially when the rail has to curve against the grain of the wood. The archaic term for the metal core is "core rail".
• baluster - A term for the vertical pickets that hold the handrail. Sometimes simply called guards or spindles. Treads often require two balusters. The second baluster is closer to the riser and is taller than the first. The extra height in the second baluster is typically in the middle between decorative elements on the baluster. That way the bottom decorative elements are aligned with the tread and the top elements are aligned with the railing angle. However, this means the first and second balusters are manufactured separately and cannot be interchanged. Balusters without decorative elements can be interchanged.
• newel - A large picket or post used to anchor the handrail. Since it is a structural element, it extends below the floor and subfloor to the bottom of the floor joists and is bolted right to the floor joist. A half-newel may be used where a railing ends in the wall. Visually, it looks like half the newel is embedded in the wall. For open landings, a newel may extend below the landing for a decorative newel drop.
• baserail - For systems where the baluster does not start at the treads, they go to a baserail. This allows for identical balusters, avoiding the second baluster problem.
• fillet - This is a decorative filler piece on the floor between balusters on a balcony railing.

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 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. This is typically used to allow stairs to change directions, or to allow the user a rest. Landings consume floor space and they are structurally floors thus 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.
• The number of steps in a set of stairs is always the number of risers, not the number of treads to avoid confusion.

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 [1]:

• 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.
• 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.
• 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.

Jacques Francois Blondel in his 1771 Cours d’architecture [1]was the first known person to establish the ergonomic relationship of tread and riser dimensions[1].

Forms

Stairs can take infinite number of forms, combining winders and landings.

The simplest form is the straight flight of stairs, without any winders nor landings. It is not often used in modern homes because:

• The upstairs is directly visible from the bottom of a straight flight of stairs.
• It is dangerous in that a fall is not stopped until the bottom of the stairs
• A straight flight requries enough space for the entire run of the stairs

Most modern stairs incorporate at least one landing. A "L" shaped stairs have one landing and a change in direction by 90 degrees. "U" shaped stairs may employ a single wider landings for a change in direction of 180 degrees, or 2 landings for two changes in direction of 90 degress each. Use of landings and a change of direction have the following advantages:

• The upstairs is not directly visible from the bottom of the stairs, providing more privacy for the upper floor.
• Falls are arrested at the landings
• Even though the landings consume total floor space, there is no large single dimension, allowing better floorplan designs

Spiral stairs wind around a central pole. They typically do not have an inner handrail, just the central pole. A squared spiral stair assumes a square stairwell and expands the steps and railing to a square, resulting in 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.

Helical or circular stairs do not have a central pole and there is a handrail on the inner side.

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.

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% as opposed to standard stairs which are almost always less than 45%. 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 [1]. The stairs are strictly employee-only.

See also Stairway to Heaven.