laid a floor of 2 x 6 inch planks, planed on both sides and matched with

tongue and groove.

This construction is shown in vertical section in Fig. 52. The girders here shown may, of course, be solid I-beams, with angle bars riveted on them for supporting the ends of the joists.

Where a lighter construction may be safely resorted to, on account of less weight to sustain, the form shown in Fig. 44 is proper. In this case an I-beam is used, say 10 to 15 inches deep, and the ends of the joists rest upon the lower flange of the beam. They should be of such depth as to project a couple of inches above the top of the beam, as shown, to provide a space for a spiking piece.

In either case the ends of the joists should be beveled as shown, so that they may drop out clear in case of fire, without displacing or warping the I-beams.

Wood joists may be dispensed with altogether, if safety from fire is of more consideration than first cost.

In this case I-beams of proper strength are laid upon the girders, or with their ends resting upon the lower flanges thereof say 4 to 8 feet from center to center and upon them are laid planed and matched floor planks from 3 x 6 inches to 5 x 8 inches, according to the distance between supports and the load to be sustained. These are bolted to the upper flange of the I-beam. This arrangement is shown in Fig. 52.

FIG. 52. Floor Supported Entirely by Steel Beams.

The vertical space occupied by these methods of construction varies considerably, as is shown in the engravings, and must be taken into account in designing the building.

Where it is desired to support floors by wooden beams, the form shown in Fig. 46 is proper. The dimensions of the beams must be sufficient to carry the load, taking into consideration also the distance between supports. The ends of the beams resting in the brick wall should be upon a "header course" of bricks, as shown, and the ends of the beam beveled off the same as if used in connection with an iron girder or I-beam, so that in case of fire the beam will fall freely out of the wall without injuring it.

Floor joists are laid upon the beams in the usual manner and spiked to them. Wooden floor joists should be braced by a "bridging" of say 2 x 3 inch scantling, as shown, placed at intervals of from 6 to 8 feet, according to the dimensions of the joists and the weights they have to support.

In using floor planks of 3 inches or over in thickness it will be found more economical to groove both edges of the planks and insert a separate piece as a tongue, than to cut a groove in one edge and a tongue in the other.

The selection of proper lumber for floors has already been referred to. It is often profitable to consider those things that have failed since it has been well said that "we learn as much by one failure as by two successes." And the failures in shop floors are prolific sources of much annoyance and

expense.

A certain machine shop floor was laid upon round chestnut timbers, flattened on top and bedded in gravel laid over "made land," that is, loosely filled in with refuse matter of any sort easy to obtain. The floor proper was of 2-inch spruce planks.

The result was that within a year the chestnut timbers and the under side of the planks began to decay, and since that time about one half of the timbers and nearly all the floor planks have been replaced each year, the patching-up process going on at intervals, and the constant result being an unsightly as well as expensive and annoying affair.

Within a hundred feet of this floor was another of 2-inch planks laid on 3 x 12 inch joists, supported on 12 x 12 inch timbers resting on piers, raising the floor about two feet above the ground.

Twelve years after this was laid some planks were removed to put in a machine foundation, and the joists and timbers were found looking nearly as fresh and new as when they came from the lumber yard.

Their elevation above the ground and the ventilation of this space by small gratings in the side walls were evidently the cause of their preservation. These cast iron gratings, say 10 x 18 inches, should be inserted at least every fifty feet in the walls of buildings whose ground floors are of wood, and at least a foot of ventilating space should be left between the ground and the floor.

Another example, equally instructive, was a second floor of a machine shop. It was of 2 x 6 inch spruce planks, properly supported. They were grooved on each edge 2-inch wide and strips were inserted as shown in Fig. 53.

The builders evidently thought that planks 24 x 6 inches, with inserted tongues, would make a good and substantial floor. And so they would have,

but the unfortunate selection of the planks included many with the grain running in the wrong direction, which caused much warping and distortion.

Fig. 54 is from a sketch taken at the head of a stairway, careful attention having been given to the direction of the grain and the distorted form of the planks. It is, perhaps, needless to say that the tongues were split, and in some cases the planks also.

FIG. 54.The Floor as Warped out of Shape.

Formerly the timbers most used in ordinary construction were of spruce. While this wood is well adapted for floor planks, it has very serious objections when used as supporting timbers. There is great liability to warp, twist, and crack as the seasoning process goes on, while its strength is not as great as some other easily obtained woods.

For instance, hard pine is superior in this respect, while it is about 35 per cent stronger than spruce, and its usual cost is only about 20 per cent greater. The foundry floor is subjected to a very considerable weight, both in molding sand and in the castings produced, but the rough usage and shocks which the machine shop floor is called upon to withstand are not met with here. Consequently there is no need of such an expensive preparation.

The ground is prepared in the same manner as for the machine shop floor, except that it is only 12 inches below the floor line. This space is first covered with a 4-inch layer of crushed stone, over which is poured a thin mixture of one part Portland cement and two parts sand, mixed rather wet.

Then a concrete is made of the same mixture and finely crushed stone, and laid to a depth of about 3 inches. On top of this is spread a flowing coat of the cement and sand mixture from to 3-inch thick, which is properly leveled off. All this having thoroughly set, the remaining portion of about 4 inches is made up of molding sand.

Pits are dug in the central portion of the foundry floor, of such number, area, and depth as the contemplated work renders necessary. The bottom is covered with 6 inches of concrete and laid with two courses of hard bricks. The side walls of the pits are 8 inches thick and are built of hard bricks, all laid in cement mortar.

The top of the wall is level with the final cement coat of the floor. It castings of ten tons or over in weight and with comparatively small bases are to be made in one of these pits it will be necessary to put down a more sub

stantial bottom.

Excavation should be made to solid ground, or "hard pan," and large stones laid in cement mortar built to within about a foot of what is to be the

bottom of the pit. Then proceed as above for making ready for the side walls. Care should be exercised in ramming or puddling, or both, to completely fill in around the side walls.

The floor of the forge shop is a still more simple matter than that of the foundry. The ground is prepared as before, and leveled off a foot below where the top of the floor is to be. This space is filled in with clean gravel mixed with clay, in the proportion of three parts of the former to one of the latter, laid down wet and thoroughly rammed down with a broad-faced

rammer.

Sharp sand, or the fine cinders from forges, are sifted over this to prevent the surface from becoming muddy when accidentally wet. In the case of a forge shop, concrete is hardly advisable, being liable to be broken up by the heavy shocks from hammers and the rough usage to which it would be subjected.

Of course it might be made thick enough to endure these conditions, but would be quite expensive and would answer the purpose no better than a hard-rammed floor of earth, as above described.

For the floor of the boiler room, flag-stones or hard-burned bricks may be used, whichever is found most convenient. If stones are used they should be cut to a certain width, in one direction at least, in order that they may be laid in courses so as to "break joints," as shown in Fig. 42. They should be from 1 to 2 inches thick.

Supposing the ground to be sufficiently solid for the purpose, it is prepared by leveling, the same as heretofore described, and at least 4 inches plus the thickness of the stones below where the top of the floor is to be. Sharp sand should be filled in 4 inches deep, and the stones laid upon this, the sand being rammed closely under each course as laid.

When completed, dry sand to the depth of inch is spread over the whole and swept back and forth to force as much as possible down through the joints. This is the cheaper and more simple method.

If it is desired to make a more substantial pavement, the earth should be leveled off at such a height that only an inch space is left between it and the stones, and an inch course of a mixture of one part Portland cement and two parts of sharp sand worked up rather soft.

The stones are laid on this while it is wet, and all spaces filled as each course is laid and leveled. Some masons may prefer to make this mixture. with a portion of lime added, the same as in cement mortar.

Should bricks be used they may be laid on either the sand or cement bed the same as described for stone, except that about half the depth of sand will be sufficient. They should be arranged in the form shown in Fig. 43, by which method they are firmly bound together, and, if laid only upon sand,

will retain their places for a long time. They are in some respects to be preferred to stone.

Where the ground is soft or has soft spots, it will be necessary to excavate to comparatively hard ground and then fill in with solid earth - preferably gravel which is to be tightly rammed or puddled to make it firm. Upon this the layer of sand may be placed as described.

It is sometimes desirable to have engine room floors paved also, and occasionally with much larger and heavier stones than those described above. They should be carefully laid in cement mortar on a good concrete bed.

If rolled iron plates, or cast iron plates are to be used they should be supported by brick piers and iron bars, or by brick walls supporting their ends, and at other points if their dimensions render it necessary.

Cast iron plates may be made with strengthening ribs on their under side, by which means the supports may be much farther apart. Plates of rolled sheet steel with raised figures of various forms and patterns can be had, which make an excellent floor for engine or boiler rooms.

The modern engine room is a much better appointed department than formerly. It should have a floor of narrow, matched hard pine, smoothly leveled off by hand planing, and the surface kept oiled with boiled linseed oil. The floor of the storehouse is of 2-inch planks, laid on 3 x 12 inch joists placed 15 inches from center to center, which in turn are supported by timbers 10 x 12 inches, placed 10 feet apart from center to center and resting on piers, leaving 15 feet between supports.

It the load which this floor is to carry warrants it, this distance should be reduced to 10 feet. The floor planks may be matched if desired, but for a floor for heavy machinery storage they need not be either matched or planed.

The carpenter shop floor is of similar construction to the above, except that the joists are 2 x 10 inches, laid 18 inches from center to center, and supported at distances of 13 feet by 8 x 10 inch timbers, resting on piers 10 feet apart.

The cupola platform or charging floor of the foundry is of 24-inch planks laid on 3 x 12 inch joists, placed 12 inches from center to center, and supported in their centers by a 10 x 12 inch beam, whose ends rest in the brick walls, and its center upon an 8 x 8 inch post. The floor, at least in the vicinity of the cupola, should be protected by sheet iron smoothly nailed down.

If preferred, the floor may be constructed entirely of iron. In this case, plate girders or I-beams should carry cross supports and the floor be composed of cast iron plates reaching from one support to the other, and having supporting ribs cast on their under sides.

This form would, of course, make a much better method of construction, and in such a situation, much safer from the danger of fire, although more expensive.