Fig. 224 is the plan of a dog-legged stair with a half-space landing. The treads of the steps in the lower flight are omitted, so as to show the strings and risers. A portion of the steps of the upper flight is broken away in order to expose to view the construction of the flight below.
The outer strings are tenoned into the newels, and so are the first and last risers of the flight.
The outer string of the upper flight and that of the lower flight are in the same vertical plane, so that if the plan of the upper flight were complete the outer string of the upper flight would overlap and hide the outer string of the lower flight.
In the same way, if the number of steps in each flight were the same, the newel, N3, of the upper flight would in plan exactly cover the newel, N, of the lower flight, being immediately over it.
The handrail in the plan is omitted as before.
Fig. 223 gives the elevation of the upper flight, and the section of the lower flight of the stairs shown in Fig. 224; but no portion of the elevation is broken away, and the treads of the lower flight are shown in section, though omitted from the plan.
The newels are fixed to trimming joists TJ, provided in the floors, and to trimmers T across the staircase at the landing.
The rough strings, RS, are framed in between these trimmers, and rough brackets, rb rb, are nailed alongside of them to support the steps.
The tread of the top step is frequently united to the boarding of the landing by a rebated joint. This is advisable if the space below the steps, known as the spandril, is to be made use of as a cupboard. In such a case the landing and the parts of all the steps should be put together with tongued joints, so that dust may be prevented from getting through them. Such joints are often used in superior work even when there is no cupboard below.1
Newel Stairs is another name given to dog-legged stairs, because the newels form a conspicuous part of the structure.
Fig. 223. Sectional Elevation on A B.
Fig. 224. Plan.
Figs. 223, 224. Dog-Legged Stairs. Scale, ¼ inch = 1 foot.
Fig. 225. Sectional Elevation on A B.
Fig. 226. Plan.
Figs. 225, 226. Open Newel Stairs. Scale ¼ inch = l foot.
Fig. 226 shows the plan of such a stair, with a quarter-space landing.
The boarding of the landing and the treads of the lower flight are omitted on plan, in order to show the construction below.
Fig. 225 is a sectional elevation on A B. The treads of the lower flight are shown in elevation though omitted from plan.
The construction of the straight portion of the stairs is similar to what has already been described. The winding steps are constructed as follows : -
Bearers, bb, carrying the risers, rr, are framed into the newels, their outer ends resting in the wall of the staircase. Between them are fixed cross bearers, cb. These would not be necessary in a narrow staircase, but are inserted in Fig. 226 for the sake of illustration.
In Figs. 226, 228 the skirting is omitted in that portion of the plan where the treads are shown.
Geometrical Stairs have no newel posts. The flights are arranged around a well hole in the centre - sometimes called an "open newel" - and each step is secured by having one end housed into the wall string, the other end resting upon the outer string, but partly deriving support from the step below it.
The handrail is uninterrupted in its course from top to bottom.
The treads for geometrical stairs should be substantial.
The string may be greatly strengthened by a flat iron bar screwed to its under side.
Figs. 227, 228 give a plan and sectional elevation of a geometrical stair with winders.
The portion of the staircase shown in Fig. 228 consists of six fliers, then eight winders, then seven more fliers, making 22 steps, leading to a half-space landing on the floor above; from this the stairs again rise, commencing with the step marked 23, the remainder being broken off to show the first flight.
The treads of the lower flight and winders are also omitted, in order to show the supports below.
The steps are formed in the way described at page 117, with (in this case) feather-tongued joints between the treads and risers.
Fig. 227. Sectional Elevation on A B C D
Fig. 228. Plan. Figs. 227, 228. Geometrical Stairs. Scale, ¼ inch = l foot.
The handrail has, as before, been omitted from the plan for the sake of clearness.
The treads and risers are housed into the wall string, the outer ends resting upon a cut and mitred string, and intermediate support is afforded by a rough string, to the side of which is nailed a rough notched bracket, cut to fit the under side of the steps, and to serve instead of brackets.
The strings themselves are framed in between the trimming joists provided in the floors, and pitching pieces, P, projecting from the wall at the level of the first and last winders; one of these latter is shown at P, but the other is covered by the fifteenth step.
The trimming joist just below No. 1 step extends of course right across the staircase - but it is in the plan (Fig. 228) supposed to be broken off just under the outer string in order to avoid confusing the plan of the curtail step.
The winders are supported throughout their length by bearers, bb, the inner ends of which are built and wedged into the wall of the staircase, the outer ends being tenoned into the circular or wreathed portion of the outer string.
The risers are nailed to these bearers, and the widest ends of the steps are supported by cross bearers dovetailed in between the risers and the longitudinal bearers above mentioned.
The lowest step of this staircase is formed with a curtailed end which, when the tread is on, in form somewhat resembles that shown in the stone staircase, Fig. 208.
In this illustration, however, the tread of the curtail step has been omitted in order to show the construction of the riser below, which is built up in a curved form, terminating in a circular block, which forms the base to support the last baluster or newel.
The inner side of the staircase is finished and embellished by a skirting notched on the under side to fit the steps, and secured to narrow grounds plugged to the wall.
In some cases two cross bearers are provided for each winder, one being framed in between the longitudinal bearers in the centre as well as that at the wide end, as in Fig. 226.
If very thick treads are used, the bearers and rough strings may be omitted altogether, the steps being wedged into the wall and projecting without further support till they reach the outer string.
Fig. 229 is a portion of a stair similar to that in Fig. 227, but with different descriptions of joints between the treads and risers, enlarged in order to show the plaster and other details, which could not be made clear upon a very small scale.
Solid steps, like those of stone, are sometimes formed in wood for geometrical staircases, and make strong but expensive work.
A Beacketed Stair is one which has ornamental brackets, B, (Tig. 230) fixed on to the end of each step above the outer string and mitred to the outer end of the riser.
They are put on merely for the sake of appearance, and play no part in supporting the steps. A Curtail Step is one of which the end is projected or curved (as shown in Tig. 205) to receive the newel balusters that support the scroll terminating the handrail. It is not unusual, especially in stone stairs, to make the last two steps of curtail form, as shown in Fig. 208; in some cases three or more steps are curtailed.
When the end of the step is circular it is called a round-ended step.
Fig. 230. Scale, 1 inch = l foot.
To avoid framing in bearers for every winding step, two or three carriages are sometimes fixed, as shown in Fig. 233, across the staircase, parallel to the fliers; to these carriages are attached rough brackets for support of the winders, wherever the latter happen to cross them.