Types of Stair Design, Stair Function and Construction
The basic forms of stairs are as follows:
Straight Flight A set of stairs sometimes with a central landing, in one direction only linking the floors.
Dogleg The flight turns on itself at a landing to go back in the reverse direction. There is no opening between the stairs therefore the landing will be double the width of the stair.
Open Well Stair This is leaving a space between the stairs. It may occur on two three or four flights or more. In effect the stair well is left open. Walls to the outside and balustrades to the inside. There is a view from floor to floor through the well.
Design Note: Where the string of a stair meets the skirting board careful attention must be given to this detail as of the two components one is structural and the other decorative. Try and get the string to match the skirting or make it a design piece (in keeping with the house decoration) on its own.
The Spiral Stair The stair rises and is supported around a central column. All the treads are tapered. These (depending on your building code) may only be used for certain situations. It also depends on the width of each tread as each tread has a minimum size that it can be to support a foot safely. Each step must be tapered. The outside width must be a wider than the inside width.
The Curved Stair This is a similar to the spiral stair in that some if not all of the treads are tapered. However the basic support system for a curved stair is as for a straight flight with outer and inner strings.
What does the stair have to do?
Obviously it has to get you from one level to the
next but it also has some other functions that are
not quite so obvious. It must be able to carry as
much load if not more than the floor it is accessing.
E.g. the piano to be moved upstairs goes via the
stair so it also copes with a live/moving load,
therefore the force exerted is not just down. It
must be large enough to take the size of all objects
and persons on the stair.
People must be able to
pass safely on the stair. It must be stable when
force is applied to the stair i.e. it can not be
allowed to have a large degree of flexibility or
movement. In many cases this stair well need to
be built from materials that do not easily catch
fire as another function of the stair is that it
is a means of escape in the case of fire.
Critical Sizes For Stairs
These will vary from country to country but generally as a rule of thumb (confirm
with the building code or regulations and all local building authorities)
the stair needs to be as wide as a doorway, 760 minimum but preferably 900
millimeters. Each riser should be no more than 160 - 165 millimeters in height
to make a reasonably comfortable stair however the riser will be determined
by the amount of going and space you have and also by the amount and type of
use of the stair. A maximum riser would be 200mm (8 inches). Each rise should
be no more than 2.4 meters.
Stair Definitions
Visit the website dedicated to stairs for more information on stair design and photographs of staircases.
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