Fig. 199 is a horizontal sectional plan (looking downwards) through step No. 12.
The steps have 9 inches tread, and 7 inches rise, and between the flights (each consisting of 9 steps) is placed a landing.
1 Sc. Piend-Check. 3 Figs. 198-214 are on a scale of 1/8 inch = l foot.
Fig. 198. Section.
Fig. 199. Plan.
Dog-Legged Stairs in stone are generally composed of hanging steps, the inner ends of which are firmly built into the walls of the staircase, while the outer ends of one flight are in the same plane as those of the other flight.
Fig. 200. Plan.
Fig. 201. Sectional Elevation on A B.
Fig. 202. Elevation.
Fig. 200 is a sectional plan (looking downwards) on the sixteenth step. Fig. 201 is a sectional elevation on the line A B, through the lower flight; and Fig. 202 is a front elevation of the stairs, showing the front of the lower flight and the back of the upper flight of steps.
1 See Note, page 104.
The stairs in Fig. 200 are shown with a half-space landing; but if the same height has to be gained when there is a smaller space available for the staircase, winders may be added so as to have only a quarter-space landing, similar to that in Fig. 226, ot the whole space may be occupied by winders as in Fig. 203.
Winders would be necessary also in case a greater height had to be gained, without increasing the area of the staircase.
Fig. 203. Plan.
Figs. 203, 204 show a dog-legged stair with winders comnmnicating between three floors, These figures make clear the importance of having a sufficient headway between the flights running in the same direction (see x y), and also between the landings (see op).
A Geometrical Stair in stone consists entirely of hanging steps, the outer ends of which are built into the walls of the staircase, while the inner ends abut upon the well hole of the stair, having no support but that derived from their successive connection, until they reach the floor.
Figs. 205, 206, 207 give illustrations of a geometrical stair in stone, with a narrow well hole, having a semicircular end. Fig. 205 is a sectional plan made through the sixteenth" step looking downwards; Fig. 206 a vertical section through the lower flight, and elevation of the upper flight beyond; and Fig. 207 a front elevation of the staircase, showing the faces of the risers of steps of lower flight, and the backs of the steps of the upper flight. The stair is constructed with spandril steps, and without a landing, except at the floors, the space being entirely filled with winders, the improved form of which, as compared with the triangular winders of the dog-legged stair, will be evident upon comparing Fig. 205 with Fig. 203.
Fig. 205. Plan.
Fig. 206. Sectional Elevation on A B.
Fig. 207. Elevation.
Fig. 208 shows a geometrical stair adapted for a large and wide staircase.
This stair consists of three flights and two quarter-space landings, besides a large and wide landing (to which the stairs lead) on the level of the floor above.
The position and direction of the steps will be easily understood from the plan, without elevations, sections, or further explanation.
In some cases the inner corners of the quarter-space landings abutting on the well hole are cut off and made in plan of a quadrant shape, by which the curve of the handrail is improved at these points.
Such a stair takes up a great deal of room, and is only suitable for large and important buildings, where sufficient space can be afforded for the staircase.
In Fig. 208 a landing of the whole width of the staircase is shown at the level of the 29 th step. Of course, if the arrangements required it, a quarter space landing at this point would be sufficient; from it would lead a flight parallel to steps 10 to 18, and running in the opposite direction.
Circular Stairs in stone may be composed either of steps supported at both ends, or of hanging steps converging toward a well hole; in either case, of course, all the steps are winders.
This newel may be either hollow or solid. Fig. 209 shows an example of a circular stair with a hollow newel, consisting of a brick cylindrical shaft into which the inner ends of the steps are pinned, the other ends being built into the outer wall of the staircase.
In some cases a thin wall is built round the centre newel, and also round the inside of the external wall, to support the ends of the steps, instead of building them in.
A very common construction, especially for circular staircases of small diameter such as those in turrets, is shown in Figs. 210, 211.
Fig. 210. Section through a,,b.
Fig. 211. Sectional Plan.
Each step is worked in the form shown in Fig. 212, with a circular portion on the inner end, having a diameter equal to that of the intended newel.
As the steps are built up the outer ends are secured in the wall of the staircase, while the circular portions at the inner extremity, being laid one upon another, give the step the required support, and form the newel of the stair.
Circular Geometrical Stairs consist entirely of hanging winders built into the outer wall of the staircase, and converging toward an open circular well hole down the centre.
Fig. 213. Plan.
Fig. 214. Sectional Elevation on A B C D.
Figs. 213, 214 show illustrations of such a stair. Fig. 213 being a sectional plan on No. 20 step, and Fig. 214 a sectional elevation.
The steps are of spandril section, except No. 1, which is necessarily square or it would have a very narrow base to rest upon.