18. The stairs shown in Fig. 15 is one of a series of flights that might be used from the basement to the top floor of a building wherein the stairs just described would be suitable in the basement. This flight represents the run between the third and fourth floors of a building as being typical of the whole stair system which is enclosed on three sides by a brick wall. In many respects the general construction is the same as in the previous example. The course to be pursued in laying out the stairs is the same as described for the previous case. The principal data to fix are (1) the size of the well; (2) the height of the story; (3) the number of risers and treads, with their height and width; and (4) the width of the stairs. The drawing is then laid out precisely as in the previous case, except that the parts in this example are numbered in the order they will be required, as is usually done with working drawings, in order to facilitate the process of erection. These numbers are marked on the plans, when laying out the stairs; and the workman, by referring to the plan, finds, for instance, that + 1 indicates the wall string which must be first put in place.

Platform Stairs 113

Fig. 13.

He consequently looks for + 1, and refers to each piece by its number instead of its name.

19. The holes indicated by the letters a and b on the plan (a), Fig. 15, are 4 inches deep for the reception of the ends of wall strings, and contain either an iron or a stone templet for the strings to bear upon. The wall string marked + 1 in the elevation (b) has a lug cast on the lower end c, through which it is bolted to the top of the beam d; at its upper end a lug e, which is shown in detail in Fig. 16 (a), is cast to receive the end of the string +2 which supports the platform and the stairs on the wall side of the second run. String + 2 has two lugs f and g cast on the lower end; f to receive the light beam which carries the platform, and g to receive the end of the face string marked + 4. on the plan. The upper end of string 2 has a lug, the same as that on +1 at e, cast on it to receive the wall string + 3. String + 3 also has on the lower part two lugs h and i; h to take a light beam to support the platform, and i to receive the face string + 5. On the upper part of + 3 is cast a flange j, through which it is bolted to the beam k; there is also a small extension or easement l cast on this string to receive the case of the finish in the hallways. Provision for allowance or variation has been made at the floor ends of the strings + 1 and + 3, as indicated.

20. The face string + 4, as shown at (a), Fig. 16, is cast with the first two newel bases attached to it, the lower one of which has a lug cast on the back, as shown at m in Fig. 16 (e), which is a detail of the development of the base, through which it is bolted to the beam. This detail shows the base of the start newel developed flat so as to show all four sides. The back a is checked out at n, so that it may fit over the flange of the beam. The inside face of the newel d, against which the first riser must fit, has a lug o. The riser p, which also extends to form the facia p', is bolted with countersunk screw bolts to the lug o. The front face of the newel c shows the section of the face string + 4 at q, and the outside of the newel b has a lug r to which the well facia t is bolted. The second newel base on string + 4 has a lug shown at u, Fig. 15 (a), cast on the outside to receive the end of the face string + 5. The end of string + 4 is bolted to the lug g on wall string + 2 (see Fig. 15). The face string + 5 has the third newel base cast with it, and extends through to the wall string + 3, to which it is bolted. The lower end is bolted to the lug u on the second newel base. On the third newel is cast a lug v, to which face string + 6 is bolted at its lower end. Face string + 6 has the base of the fourth newel cast on it, and the lugs are practically the same as those shown in the detail.

Platform Stairs 114Platform Stairs 115

(a)

Platform Stairs 116

(e)

Platform Stairs 117

(f)

Platform Stairs 118

Fig. 10.

The next pieces which demand attention are,the risers. It will be noticed, by referring to the plan (a), Fig. 15, that there are five different kinds of risers, and that each is indicated by a number commencing at seven and ending with eleven; these risers are the same as in the first example, and have been described, except those marked + 9, which have a lug cast on the back at the center to carry the outer end of the light beam + 13, which aids in the support of the platforms. The facia +12, a section of which is shown at t in Fig. 16 (e), has ribs cast 2 feet apart along the back to stiffen and support it, while clamps, which are bolted to the facia with countersunk screw bolts, are hooked over the beam. A detail, Fig. 16 (f), shows a perspective view of the string and base of the newel, with the flanges to receive the treads and risers. In the detail shown in Fig. 16 (g), w and y are sections of the face and wall strings, showing the moldings of each, the position of the slate treads, and the flanges supporting them. The railings include + 14, + 15, + 16, and + 17, shown in Fig. 15, and are the same as those described in Fig. 12. It often happens that it is necessary to introduce winding treads in the angles, instead of straight platforms. For example, had the distance between the partitions in Fig. 15 been but 11 ft. 4 1/2 in. instead of 14 ft. 10 1/2 in., the treads might still have been kept 10 1/2 inches in width by planning the comers as shown in Fig. 17. In this case the strings would take a curve which would be determined by the intersection of the treads and risers with the wall string; the elevation of these curves is shown in the section at (a) and (b), Fig. 18. The only other detail affected by the difference of conditions would be the increased length of the newels brought about by the winder risers c and d of Fig. 17, having their start at the newel, thereby lengthening it by their height, as shown in the section at (c) and (d), Fig. 18.

Platform Stairs 119

Fig. 17.

Platform Stairs 120

Fig. 18.