Demonstration of laying-out of typical stair. 

 Layout Of Typical Stairs 45. Making measurements. - 

                                                                                The principal dimensions to be ascertained in measuring for a stairway are the rise and run. The term rise denotes the extreme height between the top of the lower floor and the top of the floor above, or the actual distance to be mounted in going from one floor to another; the term run refers to the horizontal distance which the treads must cover. It depends upon the size of the riser and of the tread whether or not an "easy" flight of stairs may be built. Usually in localities where there is considerable building in progress, there are men, called stair builders, who make a specialty of this part of house construction, and who can do the work more cheaply than can the ordinary all-round workman. It is their custom to measure the building for the stairs after the floor joists are in place, as then there is less liability for mistakes. In fact, this custom is followed in every case possible in getting out any kind of finish. A carefully dimensioned sketch of the stair opening is made, and the headroom calculated at the building, if there is any doubt as to the possibility of constructing a satisfactory stairway. This sketch should include the arrangement of the treads, platforms, landings, winders, and all dimensions necessary to enable the material to be prepared accurately at the shop. 46. Laying out stairs. - For an example of the method of laying out a flight of stairs, we will imagine a room 8' in the clear between the floor and the plastered ceiling, as in
FIG#1

Fig. 1 

  1. Allowing the plaster and laths to be 3/4" Fig. 54. - Method of Laying out a Stairway. thick, the floor  joists 8" thick, and a single matched floor 7/8" thick, the entire rise of the flight will be 8' + 3/4" 4- 8" + J", which is 8' 9 5/8", or 105 5/8", = 105.625." In order to find the exact height of the riser, which is usually the first part of the stairs calculated, we assume that 14 risers will be necessary to make an easy ascent; therefore the height of each will be 105.625 ÷ 14 = 7.54", or a little more than 7 1/2". This rise may be satisfactory for a flight of stairs which has to be crowded into a small space, or where economy of space is necessary, but as it is desirable that the height of a step should be less than that, we will allow 15 risers to be used; therefore, the height of each will be 105.625 ÷ 15 = 7.04", which will make a much better rise. The height of the riser being found, the next thing is to find the width of the tread. If a straight run or a straight flight of stairs is being built, the horizontal distance between the starting and stopping points (a, of Fig. 54) may be divided into any number of treads; but if the flight has either a platform or winding treads, a plan should be sketched showing the location of the face of each riser, as in Fig. 55. A tread may be of any width sufficient to allow the foot to rest upon it safely, and the riser of any desired height not too high to reach easily by lifting the foot, but experience has shown that a certain range of proportions gives the best satisfaction. One method, as simple as any, of finding the width of the tread to fit a certain rise, is to subtract the sum of two risers from 24; the difference will equal the width of the tread. Thus, 24 - (2 X 7.04) = 9.92, practically 10; the flight would be spoken of as a 7" X 10" flight. The width of the tread is between the riser lines, as at b, b; to find the exact width of the board which is to form the tread, it will be necessary to add to this the projection of the tread beyond the riser line for the nosing or finish of the front edge of the tread, usually 1", as at I. Thus the board forming a 10" tread will actually be 11" wide, as at c, c, I, of the two lower steps. Another common method of finding the width of the tread is to divide 66 by the height of the riser; thus, 66/7 = 9 3/7", or the width of the tread. The student will see that the two most common methods give different results, therefore we may make the applications of the above rules somewhat elastic, as circumstances demand. Experience has shown that a rise of between 7" and 7 5/8", and a tread of from 9 1/2" to 10 1/2 " will give a satisfactory flight of stairs for ordinary use. For public buildings, and where the stairs are to be used by children to a great extent, the risers should be not over 7" high, and the treads should not be more than 12" wide.

FIG#2

Figure#2

Shows a place where a flight of stairs requires a platform and winders. It will be seen that there are 15 risers and 14 treads, as the upper floor takes the place of the top tread. In planning a flight of stairs, the number of risers is the first consideration, as the number and height of these determine the width of the treads, which must not be too narrow, nor too wide for safety and comfort. In this case, though a platform would be desirable at both turns, it is plain that the two winders are necessary to allow the treads of the rest of the stairs to be of a satisfactory width. An extra tread could be placed in the lower run, but to have placed another tread in the upper run, which would have been necessary if a platform had been used, would have made each of the five treads in that run too narrow. It is good practice to plan the winders so that at 18" from the post, they will be about the same width as the treads of the rest of the stairway; four winding treads will be too narrow, and two treads in the winder would be too wide for safety and comfort. Fig. 55. - Method of Turning the Angles of a Stairway. 47. Headroom. - It is necessary that judgment should be used in planning the headroom, or the vertical distance between the lower steps and the under side of the floor above (see d, d, Fig. 54), as any less than 7' 2" will not allow a large piece of furniture to be moved from one floor to another without danger of defacing the wall. Though a headroom of 6' 6" will allow a person of average height to pass without danger, any less than 7' 2" appears cramped, and is inconvenient; any more than this distance that can be allowed will add much to the appearance, as a roomy stairway gives the impression of spaciousness to the hall and to the whole house.