CHAPTER XI

THE CONSTRUCTION OF FLOORS

Earth and concrete floors. Vertical section. Stone and concrete floors. Vertical section. Paving. Simple steel supporting beams. All wood construction. How the grain of the wood should run, in planks. The wrong way to cut up the log. The right method. Quartering the log. The machine shop floor. Construction of the gallery floors. Wood joist construction. Steel construction. Floor planks. The floor that failed. Ventilation of wood floors. Another failure. The kind of wood to use. The foundry floor. Foundry pits. The forge shop floor. The boiler room floor. Kind of bricks for floor paving. Metallic floors. Engine room floor. Carpenter shop floor. The cupola platform, or charging floor. Wash room and water-closet floors. The office floors. Pattern storage floor. Kind of lumber to use. A floor of wood paving.

In the construction of modern manufacturing buildings there are many methods of constructing a floor, varying all the way from the almost primitive "dirt floor" of the forge shop to the close-jointed smoothly-finished hard wood floor of the modern watch factory.

Those which principally concern us in these articles, however, are such as are necessary in the modern machine shop, forge shop, iron foundry, etc., and these we may properly divide into six classes, viz.:

First, those composed exclusively of earth, as the floor of the forge shop. Second, those composed of earth and concrete, like the floor of an iron foundry, as shown in vertical section in Fig. 40.

Third, those of stone and concrete, as the main or ground floor of a machine shop designed for constructing and erecting heavy machinery, shown

in Fig. 41.

Fourth, those composed of stone or bricks, as required for engine and boiler rooms, etc., shown in plan in Figs. 42 and 43.

Fifth, those composed of wood, supported by iron or steel beams, as illustrated in vertical section in Fig. 44 and Fig 45.

FIG. 45.- Floor Supported by Built-up Steel Beam.

Sixth, those composed entirely of wood, as shown in Fig. 46.

There are also certain conditions which will, in a great measure, determine the kind of floor to be adopted, as, for instance, the situation, the kind of work to be done and the weights which the floor will have to support.

As to materials, there are those of each kind which it might be perfectly

proper to use in other portions of the work of construction, but which would be objectionable in a floor.

Stone should be of such nature and quality as to remain firm and hard, with no disposition to crumble away. Hence granite is the best, although there are other kinds which are nearly as good for certain purposes, and much cheaper. Generally we use such as can be obtained near the work so as to avoid the cost of transportation.

FIG. 46.- Floor with Wooden Beams.

For paving, a hard, smooth-surfaced stone is needed. Sandstone wears away easily, and therefore the harder varieties are preferable. Slate makes a very smooth-wearing and satisfactory floor. Granite is not usually employed for this purpose owing to the expense of obtaining it and the cost of cutting.

Paving bricks should be hard-burned and of a quality to insure toughness, so that they may not be easily broken by accident. Many brick companies, in different parts of the country, now manufacture bricks for street paving which possess as good wearing qualities as most kinds of stone.

Gravel should be free from soil, although a moderate quantity of sharp sand is not objectionable. When earth is used in making a floor a certain amount of clay should be added, to give an adhesive quality to the mass. Sand should in all cases be clean and sharp, free from soils and alluvial earth, and not too fine.

Lumber should be so cut at the mill that the grain of the wood shall run as nearly as possible at right angles to the face of the board or plank, as shown in Fig. 47, rather than with the grain running in a direction nearly parallel with the face, as in Fig. 48.

FIG. 47. Plank properly cut

from the Log.

FIG. 48. Plank improperly cut
from the Log.

The reason for this is that the surface of the planks shown in Fig. 48 will

wear smoothly even under very hard usage, while in the other case it will easily splinter up and present a very unsightly appearance, and will not last more than half as long as when properly cut from the log.

Then, too, while the plank shown in Fig. 47 will warp very little, if any, that in Fig. 48 has a great tendency to warp, owing to the direction of the grain, and to the fact that the sap or outer portion of a log, being the newer growth, is less dense and consequently will contract more in the process of seasoning.

Therefore the tendency is to distort the plank to the form shown by dotted lines in Fig. 48.

Logs are usually cut up at the mill on the lines shown in Fig. 49. The boards taken off at the right and left, called "sidings," are trimmed on their edges separately and sold at a reduced rate, while the remaining center portion of the log is cut into stock boards, or planks of regular width and thickness.

To preserve the direction of the grain with relation to the faces of the boards or planks, the form of cutting shown in Fig. 50 would be advisable, but not as economical. This latter method is on the principle of quartering, as referred to in the furniture makers' term of "quartered oak," for instance.

This form of cutting is shown in Fig. 51. It gives comparatively narrow boards, is expensive, and generally used for expensive woods, and for expensive work, as for fine furniture.

The main or ground floor of the machine shop being intended to sustain moderately heavy weights, both of machines and materials as well as the hard usage in moving them from place to place, and the shocks of heavy work is now usually made of concrete, and laid as shown in Fig. 41.

In some cases those portions of floor included in the side wings are constructed of wood. This form is objectionable on account of the obstruction formed by the joining of the concrete floor and the planks; for at this point the former is apt to be cracked and broken, and the latter dented, split, and defaced.

This is particularly so if the planks are a trifle higher than the concrete, as is likely to be the case when newly laid down. Then, too, where such a floor is of wood it is necessary to excavate a foot or so below the floor timbers, to provide an air space for preventing the decay of the materials.

To lay a concrete floor for this purpose the earth should be excavated to the depth of from 18 to 24 inches, according to the weights which the floor

is to carry.

For ordinary purposes of machine shop work 22 inches is desirable and sufficient. If the ground is sufficiently firm at this level, no further preparation need be made. If soft and yielding, the excavation should be carried down to solid ground, and then filled up with solid earth, or still better with gravel, the excavation being flooded with water and the filling material thoroughly puddled as it is put in.

On top of this bed should be placed a layer of coarsely broken stone, from 8 to 12 inches deep; and upon this a layer of crushed stones, none of which should exceed 2 inches in dimension. This layer should be from 4 to 6 inches thick. On this is spread a layer 2 to 4 inches thick of concrete composed of one part Portland cement, two parts clean, sharp sand, two parts clean gravel, and three parts fine crushed stone- all taken by measure, and not by weight.

These ingredients should be mixed rather wet so as to settle well down into the spaces between the stones of the previous course. The concrete should be rammed hard and made perfectly level.

Then comes a coating of from to I inch thick, consisting of a mixture of one part Portland cement and two parts clean, sharp sand, which should be laid before the former course is dry, in order that the two courses may firmly unite. This last course is laid quite wet, to facilitate "floating" - that is, the leveling off and smoothing.

Sometimes the intermediate course of concrete work is made up of shingle (coarse gravel, stones, or pebbles), mixed with hot coal tar or Portland cement; but this has the objection that, whatever be the medium used for cementing the mass, it will not adhere to the rounded surfaces of the pebbles as effectively as it does to the more porous surfaces of crushed stone.

Therefore, where subjected to hard usage, this shingle is more likely to disintegrate and break up than where crushed stone is used.

The gallery floors of the machine shop are supported on built-up girders 20 inches deep, placed at each of the columns dividing the wings from the central part of the building. Carried upon angle bars, riveted to the girders at a proper height, are the ends of 3 x 16-inch floor joists, placed 20 inches from center to center, their upper edges coming 24 inches above the top of the girders, which space is occupied by a spiking piece. On these joists is