Stairs

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Stairs , ladder , ladder , up the ladder , or just ladder is a construction designed to bridge large vertical spacing by dividing it into smaller vertical spaces, called steps . Stairs can be straight, round, or can consist of two or more straight pieces connected at an angle.

Special types of stairs include escalators and stairs. Some of the alternatives to the stairs are the elevators (lift in English English), stairlifts and tend to move the sidewalk as well as the stationary sloping sidewalk (sidewalks in English English).

Video Stairs

Components and conditions

Stairs , or stairstep is one step in the ladder. In buildings, ladder is a term applied to complete a full step between two floors. The flight of stairs is the ladder or ladder between the landing. Ladder or ladder are one or more staircases that lead from one floor to another, and include landings, newel posts, handrails, balustrades and additional sections. A ladder is a compartment that extends vertically through a building on which a ladder is placed. A ladder hall is a ladder, landing, alley, or other part of the public hall that must be skipped when going from the entrance floor to another floor of a building. The box staircase is a ladder built between walls, usually with no support except the wall strings.

Stairs may be in straight run , pointing from one floor to the other without turning or changing direction. The ladder can change direction, usually with two direct flights connected on a 90 degree angle landing. The ladder can also return to itself with a 180-degree angle landing at each end of a straight flight forming vertical stairs commonly used in high and high rise buildings. Many variations of geometry stairs can be formed from circular, elliptical and irregular construction.

The ladder may be the required exit component of the structure and building. Stairs are also provided for easy access to floors, roofs, floors, and road surfaces that are not accessible in other ways. Stairs can also be fantastic physical buildings such as the ubiquitous ladder located at Winchester Mystery House. Stairs are also subjects used in art to represent real or imaginary places built around impossible objects by using geometric distortion, as in the work of artist M. Escher.

"Stairs" are also common metaphors for the attainment or loss of positions in society; or as a hierarchy metaphor (eg Jacob's Ladder, Potemkin Warship).

Step

Each step consists of tread and wake.

Tread

Part of the stepped ladder. It's built to the same specification (thickness) like any other floor. Tread "depth" is measured from the outer edge of the step to the vertical "riser" between the steps. "Width" is measured from one side to the other.

Riser

The vertical part between each tread on the stairs. This may be lost to the "open" ladder effect.

Nosing

The end of the tread that extends above the riser below it. If anything, this means that, measured horizontally, the total "run" of the length of the ladder is not just the sum of the long treads, because the treads overlap with each other. Many building codes require stairs for commercial, industrial or city stairs as they provide anti-skid properties and enhance pedestrian safety.

Start step or Bullnose

Where the ladder opens on one or both sides, the first step on the floor or the lower landing may be wider than the other steps and rounded. The ledge usually forms a semicircle around the circumference of the rounded portion and the handle has a horizontal spiral called "volute" that supports the top of the ledge. In addition to cosmetic appeal, the initial step allows the ledge to form a wider and more stable base for the end of the handle. A sufficient hand grip ends at the post at the foot of the stairs can be less sturdy, even with thick posts. A double bullnose can be used when both sides of the ladder are open.

Stringer, Stringer board or sometimes just String

Structural members supporting the treads and stairs on the standard ladder. There are usually three stringer, one on each side and one in the middle, with more added as required for a wider range. Stringer side is sometimes dadoed to accept stairs and treads to increase support. Stringer on the open side staircase is called "cut stringer".

Winders

Winders are a narrower step on one side than others. They are used to change the direction of stairs without landing. A series of rollers form a circular staircase or spiral. When three steps are used to change the angle of 90 °, the middle step is called the kite roller as a kite-shaped square.

Crop

Various prints are used to decorate and in some instances support ladder elements. Scotia or quarter turns are usually placed under nosing to support overhangs.

Fencing System

Balustrade is a fence system and a ledge that prevents people from falling on the edge.

Banister, Railing or HandrailÃ,

A skewed member for a handle, as distinguished from a vertical ledge that holds it for a ladder open on one side; there are often fences on both sides, sometimes only on one side or not at all, on the stairs sometimes sometimes in the middle, or even more. The term "ladder holder" is sometimes used to mean simply holding a handle, or sometimes a handle and a bald or sometimes just a sketch.

VoluteÃ,

The handle element of the handle for a bullnose step that curves into like a spiral. A volute is said to be right or left-handed, depending on the side of the staircase where the handrail is when someone climbs the stairs.

Turnout

Instead of complete spiral volumes, the number of voters is a quarter of the final spin of rotation to the grip.

GooseneckÃ,

The vertical handle joining a tilted grip to a higher grip on the balcony or landing is a gooseneck.

RosetteÃ,

Where the handles end up on the wall and half-new are not used, it may be trimmed by rosettes.

Easings

Wall handrails are mounted directly to the wall with a wall bracket . At the bottom of the ladder like that is lit up to the horizontal fence and this horizontal section is called "initial easing". At the top of the stairs, the horizontal fence is called "over easing".

Core Core

Hand held wood often has a metal core to provide extra strength and stiffness, especially when rails should be curved against wood granules. The ancient term for the core is the "core rail".

BalusterÃ,

The term for a vertical post that holds a handle. Sometimes it's just called guards or spindle . Treads often require two balustrades. The second baluster is closer to riser and higher than the first. The extra height in the second baluster is usually midway between the decorative elements of the baluster. Thus the lower decorative element is aligned with the base and the upper element aligned with the fence angle.

NewelÃ,

Baluster or a large pole used to hold a handle. Because it is a structural element, it extends beneath the floor and subfloor to the bottom of the floor beam and bolted to the beam floor. A half-newel can be used where the fence ends on the wall. Visually, it looks like half a newel is embedded in the wall. For open landing, new ones can be extended under the landing for decorative decline of newel .

FinialÃ,

Decorative cover to the top of newel post, especially at the end of the floor fence.

Baserail or ShoerailÃ,

For systems where baluster does not start on the site, they head to baserail. This allows identical bald, avoiding the second widow problem.

FilletÃ,

A piece of decorative filler on the floor between the balustrades on the balcony.

Handrails may be continuous (sometimes called over-the-post ) or post-to-post (or more accurately "newel-to-newel "). For continuous handrails on long balconies, there may be some newel and tandem caps to cover the newel. In the corner, there is a quarter quarter cap . For post-to-post systems, new projects are on handrails.

The other more classic form of hand, which is still used is the tangent method. Variants of the Cylindric layout method, allowing to climb and rotate rails and easings continuously. It is defined from the principles set by architect Peter Nicholson in the 18th century.

The earliest spiral staircase appears in Temple A in the Selinunte Greek colony, Sicily, on both sides of cella. The temple was built around 480-470 BC.

Other terms

Apronà ¢

This is a wooden fascia board used to cover trimmers and beams that are exposed to a staircase. The apron can be printed or plain, and is intended to provide a cleaner viewing ladder by covering the side view.

Balcony

For staircases with an open concept upstairs or landing, the functional upper floor is a balcony. For a direct flight of stairs, the balcony may be long enough to require some newel to support the length of the fence. In a modern house, it is common to have a wooden floor on the first floor and a carpet on the second floor. Homeowners should consider using wood nosing in the carpet area. If the carpet is subsequently replaced with hardwood, the balcony railings may have to be removed to add the nostrils.

Flights

Aviation is a set of undisturbed steps.

Floating stairsÃ,

The flight of stairs is said to be "floating" if there is nothing under it. The stairs usually disappear as well to emphasize open effects, and create functional features that are suspended in the air. There may be only one stringer or stringers if not minimized. Where building codes allow, there may be no handrails.

Landing or Platform

The landing is a floor area near the stairs up or down the stairs. The landing between is a small platform built as part of a ladder between the main floor and is usually used to allow stairs to change direction, or to allow the user to rest. Half landing is where a 180 Â ° direction change is made, and a quarter landing is where 90 Â ° change of direction is made (on the intermediate landing). As middle landing consume floor space they can be expensive to build. However, changing the direction of the ladder allows the ladder to adjust where they will not otherwise, or provide privacy to the upper level because the downstairs visitor can not only see the ladder to the upper level due to a change of direction. The word 'landing' is also commonly used for common corridors on one floor above the ground floor of the building, even if the corridor is located away from the stairs.

Mobile Security Steps

Can be used as a temporary replacement, safe for many types of stairs

Runner

Carpets that run in the middle of the stairs. Runners can be directly clamped or nailed to a ladder, or can be secured by a special bar that holds the carpet in the place where the tread meets the riser, known as the staircase.

SpandrelÃ,

If there is no other ladder just below it, the triangular space under the stairs is called "spandrel". It is often used as a closet.

Staircase

This term is often reserved for the ladder itself: ladders, fences and landings; although often used interchangeably with "ladders" and "stairs". But in the UK, the term "ladder" shows what in the US is called a "ladder", but usually includes a casing - a wall, a bannister, and the underside of a ladder or roof above it.

Staircase

The term American especially is often provided for all stairs and ladders in combination; although often used interchangeably with "ladders" and "stairs".

StairwellÃ,

Spatial opening, usually vertical shaft, containing indoor staircase; with extensions often used as including the ladder it contains.

Tower of stairs

A tower attached, or put in, a building containing ladders connecting various floors.

Measurement

Measurement of stairs, especially high up and up stairs, should remain the same along the staircase.

The following ladder measures are important:

• The height increase or rises each step is measured from the top of one footprint to the next. Not the physical height of the riser; the latter excluding the thickness of the site. A person using a ladder will move this distance vertically for each step taken.
• The depth of the footprint step is measured from the edge of the nostril to the riser vertical; if the steps do not have nosing, it's the same as going; otherwise, it is a plus road with one nosing.
• The walking step is measured from the edge of the nostrils to the nosing edge in the plan view. Someone using a ladder will move this distance forward with every step they take.
• To avoid confusion, step count in a set of stairs is always the number of steps, not the number of treads.
• The total total or incoming total of the ladder is the horizontal distance from the first riser to the last riser. Often it is not just the sum of the individual palm lengths because of the overlapping nosing between the treads. If there is a N step, the total run is equal to N -1 times running: the footprint of the last step is part of the landing and is not counted.
• Increase total ladder is the height between floors (or landing) so that the ladder ladder lies. If there is a N step, the total increase equals N times the increment of each step.

• the slope or pitch ladder is the ratio between increments and occurrences (not the depth of the tread, since nosing). This is sometimes called a sweep ladder. The pitch line is an imaginary line along the tip of the nosing tread. In the UK, the scales are angles that pitch lines make with horizontal, measured in degrees. The slope value, as the ratio, is then tangent to the pitch angle.
• Headroom is the height above the nosing tread to the ceiling above it.
• The path - for curved stairs, the fingers in the curve can produce very narrow footprints. The "walking line" is an imaginary line somewhat away from the inner edges where people are expected to walk. The building code will determine its distance. The building code will then determine the minimum footprint size on the running line.

Maps Stairs

Forms

Stairs can take many forms, combining hours and landing.

The simplest form is a straight staircase, with no strong winds or landings. These types of stairs are usually used in traditional houses because they are relatively easy to build and only need to be connected at the top and bottom; However, many modern properties may not choose direct flights because:

• upstairs directly visible from the bottom of a straight staircase.
• it is potentially more dangerous because it falls undisturbed to the bottom of the stairs.
• Direct flights need enough space to run all the stairs.

Another form of a straight staircase is a space-saving ladder, also known as a paddle ladder or step ladder, which can be used for steeper hikes, but this can only be used in certain circumstances and must comply with the rules.

However, basic straight stairs are easier to design and build than with landing or winder. Although the rhythm of stepping is not interrupted in a straight run, which can offset the increased risk of falling by helping prevent mistakes in the first place, many stairs will require landing or rollers to meet safety standards in Building Regulations.

Straight ladders can have landing in the middle of the road, but it may be more common to see stairs that use landing or rollers to produce bends in stairs because a straight flight with mid landing will require a lot of linear space and more commonly found in commercial buildings. The L-shaped ladder has one landing and usually changes direction by 90 degrees. The U-shaped ladder can use a wider landing for a 180 degree direction change, or 2 landings for two changes in a 90 degree direction each. A Z-shaped ladder combines two 90 ° parallel spins, creating a shape similar to the letter 'Z' when viewed from above. The use of landing and possible change of direction has the following effect:

• The top floor is not immediately visible from under the stairs, which can give more privacy to the upper floors.
• The drop can be stopped at the point of landing, reducing the distance a person falls to reduce risk.
• Although the landing spends the total floor space, there is no requirement for a single large dimension, allowing the design of a more flexible floor plan.
• For larger stairs, especially in exterior applications, landing can provide a place to rest your feet.

Other forms include staircases with winders that bend or bend at an acute angle, three flight stairs are joined in a landing to form T-shapes, and stairs with balconies and complex designs can be produced according to individual properties.

Mono string ladder is a term used for steel spine ladder with a base.

The double rope ladder has two steel beams on both sides and a tread in the middle.

Spiral and helical staircase

The spiral staircase, sometimes referred to in the architectural description as the representative , winds around the newel (also the middle pole). They usually have a handle on the outside only, and on the inside only a central pole. A square spiral staircase assumes a rectangular staircase and extends steps and railings to square, resulting in unequal steps (larger where they extend to the corner of the square). A pure spiral assumes a circular ladder and the steps and handles are equally and positioned symmetrically. A tight spiral staircase with a central mast greatly saves space in the use of floor space.

The spiral staircase has a weakness because it is very steep - only if they are tight or otherwise are not supported by the middle column. This is for two reasons:

• The wider the spiral, the more steps you can fit per spiral. Therefore, if the spiral is large in diameter, through having a strong central support column (always large diameter) and a special handle that helps distribute the load, each step may be longer and therefore the increment between each step may be smaller. (Same as usual). Otherwise, the circumference of the circle in the running line will be so small that it is impossible to maintain normal tread depth and normal rising height without sacrificing the headroom before reaching the top floor.
• To maintain the headroom several spiral staircases have a very high increment to prop up very short diameters. This is usually the case where the ladder should be small diameter by design or should not have central support based on the design or may not have any perimeter support.

An example of perimeter support is the Vatican ladder shown in the next section or the gothic staircase shown to the left. The ladder is only tight because of its diameter should be small. Many spirals, however, have sufficient width for a normal sized footprint (8 inches) supported by a combination of center pole, supporting perimeter attached to or under tread, and helical grip. In this way, the footprint may be wide enough to accommodate the low rise. The photo on the right is a standalone ladder. This means the spiral must always be steep to allow the weight to distribute safely to the spiral in the most vertical way. Spiral steps with column center or perimeter support do not have these restrictions. Building codes may limit the use of a spiral staircase to a small area or a secondary use if the tread is not wide enough or has risers above 9 and a half inches.

The term "spiral" has a narrower definition in the context of mathematics, since the mathematical spiral lies in one plane and moves toward or away from the center. The term math for the motion in which the locus remains at a fixed distance from the fixed line while moving in a circular motion about it is "helix". The presence or the central pole does not affect the terminology applied to the design of the structure.

The medieval spiral staircase is generally made of stone and usually curved clockwise (from the conqueror's point of view), to place the attacking sword (most often using the right hand) in a less favorable position. This lack of symmetry forced the right-handed swordsman to involve the central spear and lowered his mobility compared to the defender who was descending the stairs. Examples from the 14th to the seventeenth century of these staircases can be seen in Muchalls Castle, Crathes Castle, and Myres Castle in Scotland. However, exceptions to the rule exist, as can be seen in the accompanying Scala Palazzo Contarini del Bovolo image, which rotates counter-clockwise.

Developments in manufacturing and design have led to the introduction of spiral staircase shaped kits. Steps and handrails can be bolted together to form a complete unit. These stairs can be made of steel, wood, concrete or any combination of materials.

The helical or circular ladder does not have a central mast and there are handles on both sides. It has the advantage of a more uniform tread width when compared to a spiral staircase. Such stairs can also be built around elliptical or oval planforms.

Both double and double helix are possible, with two independent helical stairs in the same vertical space, allowing one person to climb and another to descend, without ever meeting if they select different helices. For example, Pozzo di S. Patrizio allows one-way traffic so that the laden and untidy lags can rise and fall unhindered, while ChÃÆ'Â ¢ teau de Chambord, ChÃÆ' Â ¢ teau de Blois, and the headquarters of CrÃÆ'Ã… © dit Lyonnais ensure separation for social purposes. The fled fire, although built with landing and straight staircases, often serves as a double helix, with two separate stairways interwoven and occupying the same floor space. This often supports the legal requirement to have two separate fire exits.

Both spiral and helical stairs can be characterized by the number of turns made. The "quarter-turn" ladder places a person who faces 90 degrees from the original orientation. Likewise, there are half rounds, three quarters of a turn, and a full swivel staircase. Continuous spirals can make many rounds depending on the height. A very high multi-turn spiral staircase is usually found in old stone towers inside fortresses, churches and on lighthouses.

Winders can be used in combination with a straight staircase to change the direction of the stairs. This allows a large number of permutations.

Alternate footstool

Where there is insufficient space for the full length of the normal ladder, the staircase back and forth can be used. Alternative tread ladders allow the ladder to come down safely from a very steep staircase. Treads are made in such a way that they alternate between footprints for each leg: one wide step on the left side; the next step is wide on the right side. There is not enough space on the narrowest of steps for the other foot to stand up, so the person should always use the correct legs at the correct pace. The slope of the staircase back and forth can be as high as 65 degrees compared to the standard ladder which is almost always less than 45 degrees. The advantage of stepping stairs back and forth is that people can come down facing forward. The only other alternative in such short spaces is the ladder that needs the descendants facing backwards. Alternative stair treads may not be safe for small children, elderly or physically challenged. Building codes usually classify them as ladders and will only allow them where stairs are allowed, usually basements or attic utilities or storage areas are not accessed often.

The image on the right illustrates the efficiency of the space obtained by the alternating stair steps. Stair treads back and forth appear in the center of the drawing, with a green tread. The back and forth staircase requires one unit of space per step: equal to the half-width step on the left, and half as many full width stairs to the right. Thus, the horizontal distance between the steps in this case is reduced by a factor of two, reducing the size of each step.

The horizontal distance between the steps is reduced by a factor of less than two if for construction reasons there are narrow "unused" steps.

Often there are (here too) glide plane symmetry: a mirror image of a vertical center plane corresponding to a one-step shift.

Alternate footprint stairs have been in use since at least 1888.

src: i.imgur.com

Ergonomics and building code requirements

Ergonomically and for security reasons, the ladder must have a certain size so that people can use it comfortably. Building codes usually specify a certain size so that the stairs are not too steep or narrow.

Nicolas-FranÃÆ'§ois Blondel in his final volume Cours d'architecture (1675-1683) was the first person known to establish an ergonomic relationship of the tread and wake dimensions. He mentioned that 2 x riser footprint = step length.

It is estimated that missteps occur once in 7,398 uses and minor accidents on stairs occur once in 63,000 usages. Some people choose to live in a place without a ladder so that they are protected from an injured ladder can be a dangerous obstacle for some people.

The stairs are not suitable for wheelchairs and other vehicles. Stairlift is a mechanical device for lifting wheelchairs up and down stairs. For stairs that are wide enough, the rail is mounted to the tread ladder, or attached to the wall. The chair is attached to the rail and the person in the chair is lifted as the seat moves along the tracks.

UK requirements

(K-approved Approved document and Stage Controller)

Documents approved by the ladder categorises as 'Private', 'Institutional or assemblies' and 'other'

When considering a ladder for a private residence

Building rules are required for stairs used where the floor difference is greater than 600 mm (23.6 inches)

Ladder slope - Ride and Walk - Every increase between 155 and 220 mm (6.1 and 8.7 inches) is used with walks between 245 and 260 mm (9.6 and 10.2 inches) inch) or a ride between 165 and 200 mm (6.5 and 7.9 inches) is used with each occurring between 223 and 300 mm (8.8 and 11.8 inches)

Maximum Rise 220 mm (8.7 inches) and Minimum Going 220 mm (8.7 inches) given that the maximum pitch of the private ladder is 42 Â °. The normal relationship between the rising and rising dimensions is that two plus increments go (2R G) should be between 550 and 700 mm (21.7 and 27.6 inches)

Step construction - Steps should have a tread level; they may have open risers but if the tread should have to overlap at least 16 mm (0.6 inches). Private domestic ladders tend to be used by children under 5 years old so that hand ballast ballater distance should be built so that the 100 mm (3.9 inch) diameter ball can not pass through the opening on the ladder to prevent children from sticking their heads through and potentially jammed.

Headroom - 2 m (78.7 inches) headroom is sufficient. Special consideration may be made for loft conversion.

Flight width - No recommendations are given for the width of the stairs.

Flight length - Approved documents refer to 16 steps (stairs) for stairs in a shop or assembly building. There is no requirement for a private ladder. In practice there will be less than 16 steps as 16 x 220 mm (8.7 in) giving over 3.5 m (137.8 in) the total increase far above that in domestic situation.

Landings - Unobstructed landing levels should be provided at the top and bottom of each flight. Width and length at least of the width of the stairs and may include part of the floor. A door can swing across the landing at the bottom of the flight but must leave clear space at least 400 mm (15.7 inches) across the landing

Tapered steps - There is a special rule for the ladder with a tapered step as shown in the picture above Stairs Mushroom Above

Alternate tread steps can be provided in space saving situations

Keep - Flight and landing must be maintained on the side where the fall is more than 600 mm (23.6 inches). Since the domestic private ladder is likely to be used by children under 5 guards should be constructed so that a ball of 100 mm (3.9 inches) in diameter can not pass through every hole or built so that children will not be able to climb guard. The height for the internal private ladder should be at least 900 mm (35.4 inches) and capable of withstanding the horizontal force of 0.36 kN/m (2.1 lbf/in).

Industry guidelines in designing the ladder to English Regulations and Standards.

US requirements

American building codes, while varying from State to State and County to County, generally specify the following parameters:

• The minimum tread length, usually 9 inches (229 mm) does not include the nostrils for private residences. Some building codes also set a minimum wake height, often 5 inches (127 mm).
• Riser-Tread Formula: Sometimes the ladder parameter will be something like a riser plus tread equal to 17-18 inches (432-457 mm); Another formula is 2 times the tread riser equals 24.6 inches (625 mm), the length of the step. Thus a 7-inch (178 mm) increase and a 10.6-inch (269 mm) footprint exactly meets this code. If only 2 inches (51 mm) is used then a 20.6 inch (523 mm) footprint is required. This is based on the principle that low rise is more like walking on a gentle slope and so the natural swings of the feet will be longer.
• Low-rise stairs are very expensive in terms of space consumed. Such a low ladder was built into Winchester Mystery House to accommodate the weakness of the owner, Sarah Winchester, before the invention of the elevator. This ladder, called "Easy Risers" consists of five flights wrapped in a multi-turn arrangement with a total width equal to more than four times the width of an individual flight and a depth that is roughly equal to one flight run plus this width. Flights have varying number of steps.
• Tilt: Values ​​for a rise-to-tread ratio of 17/29 ~ 0.59 are considered optimal; this corresponds to a slope angle of about 30 °.
• The variance at riser height and depth of tread between steps on the same flight should be very low. Building codes require a variance no greater than 0.1875 inches (4.76 mm) between adjacent tread depths or adjacent ladder height; in flight, the tolerance between the largest and smallest riser or between the largest and smallest footprint should not exceed 0.375 inches (9.5 mm). The reason is on a continuous flight, people get used to the usual steps and can stumble if there are different steps, especially at night. The general rule is that all the steps on the same flight must be identical. Therefore, stairs are usually made specifically to fit a special floor for floor height and available horizontal space. Particular attention should be taken on the first and last rungs. The ladder should be supported directly by the subfloor. If a thick floor (eg thick wooden board) is added over a 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 reaches only the subfloor and the thick floor is added, the last rise at the top may be higher than the last riser. The first and last riding height of the rough ladder is modified to match the addition of the finished floor.
• Projection of the maximum nose, usually 1.25 inches (32 mm) to prevent people tripping on nosing.
• Grip height. This is usually between 34 and 38 inches (864 and 965 mm), measured into the nose of the site. The minimum handrail height for the landing may be different and usually 36 inches (914 mm).
• Diameter of handle. The size should be comfortable to hold and usually between 1.25 and 2.675 inches (31.8 and 67.9 mm).
• Maximum distance between the handles. This is usually 4 inches (102 mm).
• The opening (if present) between the bottom rail and the tread is usually no larger than 6 inches (152 mm).
• Headroom: At least 83 inches (211Ã, cm).
• Maximum vertical height between floors or landing. It allows people to rest and limit the height of the fall.
• Handhold mandates if there are more than a few steps (usually 2 steps)
• Minimum width of stairs, with and without handrails
• Not allowing swinging doors on stairs; the door bow should be actually on the floor/landing.
• The ladder can be designated as a refuge and fire escape route, due to its fireproof design and fresh air supply.
• The American Disabilities Act and other state accessibility standards (such as TAS) do not allow overseers on accessible or exit stairs.

src: i.ytimg.com

Stairs and art

Source of the article : Wikipedia