N.B. - In the Figures connected with stairs the handrail is drawn in the elevations and sections in order more clearly to show the direction of the steps, but omitted from the plans so as not to obscure them.
A Straight Stair is one in which all the steps are parallel to one another and rise in the same direction - thus a person ascending moves forward in a straight line.
Such a stair is, for some reasons, very convenient, but can only be used when there is a considerable length of space available for the staircase compared with the height to be gained.
When this is not the case, the flights of steps are made to run in different directions, so that they are doubled up into a shorter space.
Flights running alternately in opposite directions are found to be a great relief in ascending a considerable height, and therefore a very long straight stair is objectionable.
A Dog-legged Stair1 is so called from its being bent or crooked suddenly round in fancied resemblance to a dog's leg.
In this form of stair the alternate flights rise in opposite directions, as indicated by the arrows in Figs. 200, 203, and 224.
The ends of the steps composing each of these alternate flights are in the same plane with those of the other flight, so that there is no opening or well hole between them.
It is evident that - putting landings out of consideration - dog-legged stairs require only half the length of staircase that would be occupied by an equal number of steps of the same size arranged as a straight stair. On the other hand, the dog-legged stair requires twice the width of the straight stair.
Figs. 200-202 show a dog-legged stair in stone with a half-space landing. Figs. 223, 224 show a similar stair in wood.
1 This term is generally used with reference to wooden stairs, but there is no distinct name for stone stairs of similar form. Stairs with rectangular well holes, such as those in Figs. 208, 216, are sometimes called dog-legged.
In Fig. 203 there is no intermediate landing, the whole space being taken up with winders.
It will be noticed that all the winders converge to a point in the stair itself, so that they are very narrow near this end, and most inconvenient to ascend. This is a great drawback to the dog-legged form of stair, which, indeed, should never be used when winders are required, if there is room for a well hole between the flights.
A Geometrical Stair is one in which there is an opening or well hole between the backward and forward flights.
Such a stair requires of course a little more width, but only about the same length of space as a dog-legged stair.
The effect of the well hole is that the winders converge to a point between the flights, and have a certain amount of width even on the verge of the well hole. At a short distance inwards, where the person ascending places his foot, the winder is so broad as to afford a very convenient tread.
Figs. 205-207 show a geometrical stair in stone without intermediate landings, the space being occupied entirely by winders. Fig. 228 shows a similar stair constructed in wood.
Circular Stairs are composed of steps contained in a circular or polygonal staircase, towards the centre of which they all converge.
AU the steps are necessarily winders.1
A Circular Newel Stair is one in which the converging steps are supported by a newel at the centre of the staircase.
This newel may be either solid or hollow (see page 112).
A Circular Geometrical Stair is in form the same as the last described, but that there is no newel. The steps converge as before, but rise round an open well hole instead of resting upon a newel (page 113).