Stair safety -rise and going
For the purpose of the following examples we will look at the regulations for If we refer to the regulations we can choose a riser height between mm and mm. a normal relationship between the dimensions of the rise and going is: . The findings indicate that there is a relationship between the human pace and the riser-tread ratio, but the relationship is more flexible than Blondel envisaged. A stairway, staircase, stairwell, flight of stairs, or simply stairs, is a construction designed to .. The normal relationship between dimensions of the rise and going is that twice the rise plus the going (2R + G) should be between and mm.
How many songs, like Led Zeppelin's Stairway to Heaven, reference stairs? What about artwork like M. Escher's Relativity, or Marcel Duchamp's Nude Descending a Staircase, that include or feature these architectural elements?
Parts of a Staircase The basic components of a staircase are the tread; the horizontal surface we walk on, the riser; the vertical part between each tread, and the stringer; a structural support that holds the treads in place and provides stability.
What we call a step is actually a combination of a tread and a riser, or one step up or down from our previous position. In some cases, such as open stairs, the riser is missing and we can see through the stairs. Diagram of a staircase Optional Elements of a Staircase Other, optional parts of a staircase include the nosing, banister, and balusters. Nosing is a small part of a tread that overhangs the riser. The banister, which is also called a railing or a handrail, is both a decorative and a safety feature that prevents people from falling off the side of a staircase or allows them to hold on for stability.
Some handrails are attached directly to a wall while others are positioned on the open part of the staircase. When they are on the open part, the banister is held up by balusters, vertical supports attached to a tread at the bottom and the banister at the top.
Different Types of Steps There are also different types of steps, determined by the shape of tread. The basic step involves a rectangular tread. The most common variation of a simple step is a winder.
These involve treads that are wider on one side than the other. 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. The photo on the right are self-supporting stairs. This means the spiral needs to be necessarily steep to allow the weight to distribute safely down the spiral in the most vertical manner possible.
Stairway risers and treads: acceptable and preferred dimensions.
Spiral steps with center columns or perimeter support do not have this limitation. Building codes may limit the use of spiral stairs to small areas or secondary usage if their treads are not sufficiently wide or have risers above 9 and a half inches. The mathematical term for motion where the locus remains at a fixed distance from a fixed line whilst moving in a circular motion about it is " helical ".
The presence or otherwise of a central pole does not affect the terminology applied to the design of the structure. Spiral stairs in medieval times were generally made of stone and typically wound in a clockwise direction from the ascender's point of view   to place attacking swordsmen who were most often right-handed at a disadvantage. This asymmetry forces the right-handed swordsman to engage the central pike and degrade his mobility compared with the defender who is facing down the stairs.
Exceptions to the rule exist, however, as may be seen in the accompanying image of the Scala of the Palazzo Contarini del Bovolowhich winds up counter-clockwise. Developments in manufacturing and design have led to the introduction of kit form spiral stairs. Steps and handrails can be bolted together to form a complete unit.
These stairs can be made out of steel, timber, concrete or a combination of materials. 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 elliptical or oval planform. The 'Bramante' staircaseVatican museumsshowing the two access points at the bottom of the stairs Both double spiral and double helix staircases are possible, with two independent helical stairs in the same vertical space, allowing one person to ascend and another to descend, without ever meeting if they choose different helices.
For examples, the Pozzo di S. Fire escapes, though built with landings and straight runs of stairs, are often functionally double helices, with two separate stairs intertwined and occupying the same floor space. This is often in support of legal requirements to have two separate fire escapes. 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 fortificationschurches and in lighthouses.
Winders may be used in combination with straight stairs to turn the direction of the stairs. This allows for a large number of permutations.
Stairway risers and treads: acceptable and preferred dimensions.
Alternating tread stairs[ edit ] An alternating tread stair center between a half-width stair left and full-width stair rightbuilt with Duplo blocks. An alternating tread stair climbing the steep slope of a pinnacle in Pinnacles National ParkCaliforniaUnited States. Where there is insufficient space for the full run length of normal stairs, alternating tread stairs may be used.
Alternating tread stairs allow for a safe forward-facing descent of very steep stairs. The treads are designed such that they alternate between treads for each foot: 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. Alternating tread stairs may not be safe for small childrenthe elderly or the physically challenged.
Building codes typically classify them as ladders and will only allow them where ladders are allowed, usually basement or attic utility or storage areas not frequently accessed. The image on the right illustrates the space efficiency gained by an alternating tread stair. The alternating tread stair appears in the image's center, with green-colored treads.
The alternating stair requires one unit of space per step: Thus, the horizontal distance between steps is in this case reduced by a factor of two, reducing the size of each step. The horizontal distance between steps is reduced by a factor less than two if for construction reasons there are narrow "unused" steps.
There is often here also glide plane symmetry: Alternating tread stairs have been in use since at least