Читать книгу Stair-Building and the Steel Square - Fred. T. Hodgson - Страница 5

Before proceeding further with the subject, it is essential that the student make himself familiar with a few of the terms used in stair-building.

Fig. 1. Illustrating Rise, Run,

and Pitch.

The term rise and run is often used, and indicates certain dimensions of the stairway. Fig. 1 will illustrate exactly what is meant; the line A B shows the run, or the length over the floor the stairs will occupy. From B to C is the rise, or the total height from top of lower floor to top of upper floor.[A] The line D is the pitch or line of nosings, showing the angle of inclination of the stairs. On the three lines shown—the run, the rise, and the pitch—depends the whole system of stair-building.

The body or staircase is the room or space in which the stairway is contained. This may be a space including the width and length of the stairway only, in which case it is called a close stairway, no rail or baluster being necessary. Or the stairway may be in a large apartment, such as a passage or hall, or even in a large room, openings being left in the upper floors so as to allow road room for persons on the stairway, and to furnish communication between the stairways and the different stories of the building. In such cases we have what are known as open stairways, from the fact that they are not closed on both sides, the steps showing their ends at one side, while on the other side they are generally placed against the wall.

Sometimes stairways are left open on both sides, a practice not uncommon in hotels, public halls, and steamships. When such stairs are employed, the openings in the upper floor should be well trimmed with joists or beams somewhat stronger than the ordinary joists used in the same floor, as will be explained further on.

Tread. This is the horizontal, upper surface of the step, upon which the foot is placed. In other words, it is the piece of material that forms the step, and is generally from 1¼ to 3 inches thick, and made of a width and length to suit the position for which it is intended. In small houses, the treads are usually made of ⅞-inch stuff.

Riser. This is the vertical height of the step. The riser is generally made of thinner stuff than the tread, and, as a rule, is not so heavy. Its duty is to connect the treads together, and to give the stairs strength and solidity.

Rise and Run. This term, as already explained, is used to indicate the horizontal and vertical dimensions of the stairway, the rise meaning the height from the top of the lower floor to the top of the second floor; and the run meaning the horizontal distance from the face of the first riser to the face of the last or top riser, or, in other words, the distance between the face of the first riser and the point where a plumb line from the face of the top riser would strike the floor. It is, in fact, simply the distance that the treads would make if put side by side and measured together—without, of course, taking in the nosings.

Suppose there are fifteen treads, each being 11 inches wide; this would make a run of 15 × 11 = 165 inches = 13 feet 9 inches. Sometimes this distance is called the going of the stair; this, however, is an English term, seldom used in America, and when used, refers as frequently to the length of the single tread as it does to the run of the stairway.

String-Board. This is the board forming the side of the stairway, connecting with, and supporting the ends of the steps. Where the steps are housed, or grooved into the board, it is known by the term housed string; and when it is cut through for the tread to rest upon, and is mitered to the riser, it is known by the term cut and mitered string. The dimensions of the lumber generally used for the purpose in practical work, are 9½ inches width and ⅞-inch thickness. In the first-class stairways the thickness is usually 1⅛ inches, for both front and wall strings.

Fig. 2. Common Method

of Joining Risers

and Treads.

Fig. 2 shows the manner in which most stair-builders put their risers and treads together. T and T show the treads; R and R, the risers; S and S, the string; O and O, the cove mouldings under the nosings X and X. B and B show the blocks that hold the treads and risers together; these blocks should be from 4 to 6 inches long, and made of very dry wood; their section may be from 1 to 2 inches square. On a tread 3 feet long, three of these blocks should be used at about equal distances apart, putting the two outside ones about 6 inches from the strings. They are glued up tight into the angle. First warm the blocks; next coat two adjoining sides with good, strong glue; then put them in position, and nail them firmly to both tread and riser. It will be noticed that the riser has a lip on the upper edge, which enters into a groove in the tread. This lip is generally about ⅜-inch long, and may be ⅜-inch or ½-inch in thickness. Care must be taken in getting out the risers, that they shall not be made too narrow, as allowance must be made for the lip.

Fig.3 Vertical Section of Stair Steps.

Fig. 4. End Section of Riser.	Fig. 5. End Section of Tread.

If the riser is a little too wide, this will do no harm, as the over-width may hang down below the tread; but it must be cut the exact width where it rests on the string. The treads must be made the exact width required, before they are grooved or have the nosing worked on the outer edge. The lip or tongue on the riser should fit snugly in the groove, and should bottom. By following these last instructions and seeing that the blocks are well glued in, a good solid job will be the result.

Fig. 3 is a vertical section of stair steps in which the risers are shown tongued into the under side of the tread, as in Fig. 2, and also the tread tongued into the face of the riser. This last method is in general use throughout the country. The stair-builder, when he has steps of this kind to construct, needs to be very careful to secure the exact width for tread and riser, including the tongue on each. The usual method, in getting the parts prepared, is to make a pattern showing the end section of each. The millman, with these patterns to guide him, will be able to run the material through the machine without any danger of leaving it either too wide or too narrow; while, if he is left to himself without patterns, he is liable to make mistakes. These patterns are illustrated in Figs. 4 and 5 respectively, and, as shown, are merely end sections of riser and tread.

Fig. 6. Side Elevation of Finished Steps with Return Nosings and Cove Moulding.

Fig. 7. Front Elevation of Finished Steps.

Fig. 6 is a side elevation of the steps as finished, with return nosings and cove moulding complete.

A front elevation of the finished step is shown in Fig. 7, the nosing and riser returning against the base of the newel post. Often the newel post projects past the riser, in front; and when such is the case, the riser and nosing are cut square against the base of the newel.

Fig. 8. Portion of a Cut and

Mitered String, Showing

Method of Constructing

Stairs.

Fig. 8 shows a portion of a cut and mitered string, which will give an excellent idea of the method of construction. The letter O shows the nosing, F the return nosing with a bracket terminating against it. These brackets are about ⁵⁄₁₆-inch thick, and are planted (nailed) on the string; the brackets miter with the ends of the risers; the ends of the brackets which miter with the risers, are to be the same height as the riser. The lower ends of two balusters are shown at G G; and the dovetails or mortises to receive these are shown at E E. Generally two balusters are placed on each tread, as shown; but there are sometimes instances in which three are used, while in others only one baluster is made use of.

An end portion of a cut and mitered string is shown in Fig. 9, with part of the string taken away, showing the carriage—a rough piece of lumber to which the finished string is nailed or otherwise fastened. At C is shown the return nosing, and the manner in which the work is finished. A rough bracket is sometimes nailed on the carriage, as shown at D, to support the tread. The balusters are shown dovetailed into the ends of the treads, and are either glued or nailed in place, or both. On the lower edge of string, at B, is a return bead or moulding. It will be noticed that the rough carriage is cut in snugly against the floor joist.

Fig. 9. End Portion of Cut and

Mitered String, with Part

Removed to Show Carriage.

Fig. 10 is a plan of the portion of a stairway shown in Fig. 9. Here the position of the string, bracket, riser, and tread can be seen. At the lower step is shown how to miter the riser to the string; and at the second step is shown how to miter it to the bracket.

Fig. 11 shows a quick method of marking the ends of the treads for the dovetails for balusters. The templet A is made of some thin material, preferably zinc or hardwood. The dovetails are outlined as shown, and the intervening portions of the material are cut away, leaving the dovetail portions solid. The templet is then nailed or screwed to a gauge-block E, when the whole is ready for use. The method of using is clearly indicated in the illustration.

Strings. There are two main kinds of stair strings—wall strings and cut strings. These are divided, again, under other names, as housed strings, notched strings, staved strings, and rough strings.

Wall strings are the supporters of the ends of the treads and risers that are against the wall; these strings may be at both ends of the treads and risers, or they may be at one end only. They may be housed (grooved) or left solid. When housed, the treads and risers are keyed into them, and glued and blocked. When left solid, they have a rough string or carriage spiked or screwed to them, to lend additional support to the ends of risers and treads. Stairs made after this fashion are generally of a rough, strong kind, and are especially adapted for use in factories, shops, and warehouses, where strength and rigidity are of more importance than mere external appearance.

Open strings are outside strings or supports, and are cut to the proper angles for receiving the ends of the treads and risers. It is over a string of this sort that the rail and balusters range; it is also on such a string that all nosings return; hence, in some localities, an open string is known as a return string.

Fig. 10. Plan of Portion of Stair.

Fig. 11. Templet Used to Mark

Dovetail Cuts for Balusters.

Housed strings are those that have grooves cut in them to receive the ends of treads and risers. As a general thing, wall strings are housed. The housings are made from ⅝ to ¾ inch deep, and the lines at top of tread and face of riser are made to correspond with the lines of riser and tread when in position. The back lines of the housings are so located that a taper wedge may be driven in so as to force the tread and riser close to the face shoulders, thus making a tight joint.

Rough strings are cut from undressed plank, and are used for strengthening the stairs. Sometimes a combination of rough-cut strings is used for circular or geometrical stairs, and, when framed together, forms the support or carriage of the stairs.

Staved strings are built up strings, and are composed of narrow pieces glued, nailed, or bolted together so as to form a portion of a cylinder. These are sometimes used for circular stairs, though in ordinary practice the circular part of a string is a part of the main string bent around a cylinder to give it the right curve.

Notched strings are strings that carry only treads. They are generally somewhat narrower than the treads, and are housed across their entire width. A sample of this kind of string is the side of a common step-ladder. Strings of this sort are used chiefly in cellars, or for steps intended for similar purposes.

[A] Note.—The measure for the rise of a stairway must always be taken from the top of one floor to the top of the next.