3. In stair building, a riser and tread together are termed a step, the riser being the upright portion which supports the tread, or horizontal part, upon which the foot is placed. The nosing is the projection of the tread beyond the face of the riser.

The term run is applied to the aggregate width of the treads.

Where the risers are parallel to each other on plan, thus forming straight steps, the steps are called fliers; but where the risers radiate on plan, forming triangular treads, the steps are called winders.

The term flight designates a succession of steps between one starting place and the one next above it. The spaces wider than steps, which constitute resting places between the flights, or which are the terminations of the stairways, are termed landings, or platforms. If the landing is square and occupies half the width of the stairway, it is called a quarter-space landing; but when it takes in the full width of the stairway, it is called a half-space landing. The space required for landings is sometimes filled in by winders; this is especially the case in geometrical stairways and those in which the run is limited. In every case, it is the quantity of space in the run that decides the nature of the landing, whether it is to be quarter or half space, or filled in with winders. Where the run is unlimited, a half-space landing should be adopted; but where the run does not allow this kind of landing, a quarter space is preferable to winders, as the latter should never be put in a stairway when they can be avoided.

The lower step of a flight sometimes has its outer end in the form of a horizontal spiral, and is then termed a curtail step. When the lower step is rounded to a semicircle, it is known as a hull-nose step. Where steps have an outward curve, they are called swelled steps; this form is generally used when the front stringer is curved out at the starting of the stairway.

If, in ascending a stairway, the hand rail is on the right-hand side, the stairway is called a right-hand stairway. If the hand rail is on the left-hand side, the stairway is called a left-hand stairway.

The above are some of the more common terms used in stair building ; others will be explained as occasion arises for their use.

4. Stairways arc known as dog leg, open newel, and geometrical. A dog-leg stairway has no well hole, and the stringer of the tipper flight is vertically over that of the lower one. A well hole is the space on plan between two flights when the stringers are not located in the same vertical plane. The objection to dog-leg stairways is that the hand rail is not continuous, but strikes the soffit of the upper flight.

Where newels are placed at the angles of the well hole, the stairway is termed an open-newel stairway; but when the stringer is continued in a curve perpendicular to the curve on the plan round the winders, the stringer is said to be wreathed, and the stairway is designated as geometrical.

.1. The above classification relates more especially to the general design than to the structural details, many of which are common to each. When classified with relation to the methods of construction, there are two system; the first consists in the use of rough timbers, or carriages, cut to the angle of intersection between the treads and risers, as shown in Fig. 1; the other, which is the more generally used, has the treads and risers grooved, or housed, from 3/8 to 1/4 inch, into the prepared stringers. In the first case, the treads and risers are nailed on the carriages, and, where they intersect with the wall, a board of the same thickness as the baseboard connecting with the stairway is scribed, or cut, to the required outline so as to fit closely the angles of treads and risers; this runs the full length of the stairway, forming what is termed the wall stringer. In favor of this method of construction are its simplicity and strength. Against its adoption may be adduced the great difficulty of satisfactorily scribing the wall stringers, and even when this is successfully done, the stairway is likely, in time, through shrinkage and jarring, to show imperfections.

Fig. 1.

The carriages, also called horses and springing trees, for the second form of construction of stairways, are not cut to the angle of treads and risers, as is the case in the first method, but are simply straight scantlings of sufficient strength to support the stairway and its probable load, rough brackets being nailed on the sides of these scantlings and fitted tightly under each tread, as shown at a, Fig. 2. In some cases, where the treads and risers are enclosed in stringers, the wall stringer only is housed to receive the treads and risers, the front, or outer, stringer being cut square to receive the tread, and mitered to receive the riser. When thus prepared the front stringer is termed a cut-and-mitered, or open, stringer, the wall stringer being termed a housed stringer. Occasionally both wall and front stringers are housed, in which case the front stringer is said to be a close stringer. Geometrical stairways are seldom thus constructed, the method being mostly confined to dog-leg and open-newel stairways.

Fig. 2.

In geometrical stairways, the front stringer is cut and mitered so as to meet the conditions arising from the wreathed portion of the stringer and rail, which are assumed to stand perpendicular to each other and in the same vertical plane. The rail in this case is wholly supported by the balusters, instead of by the newel, and the cut-and-mitered stringer affords a substantial footing to the balusters, which are dovetailed, glued, and nailed to the ends of treads; the nosing and molding of the treads being returned their full width on the face of the stringer. Stairs thus constructed are said to have nosed and mitered moldings, and when brackets are placed along the front stringer below the nosing the stairway is known as a bracketed stairway.