with it, should be laid a 1-inch hard wood floor, which may be readily renewed when it is worn out. The floor timbers and the top floor should run lengthwise of the building and the 3-inch planks crosswise.

A concrete floor may be laid in the central portion, and the above method of plank floor be laid in the side portions.

Where the machinery to be used in the side portions of the building is of moderate weight, and the stock to be handled therein is not particularly heavy, the foundations for the floor need not be of such a substantial character as that described. Probably four or six inches of broken stone or cinders will be quite sufficient for the purpose. The floor planks, too, may be lighter. say 2-inch for the main floor and 1 for the top floor, and the floor timbers 4 X 4 inches.

It is assumed that in all cases the ground has been properly prepared and leveled up before the crushed stone or cinder bed is put down. For this very necessary preparation the reader is referred to the chapter on foundations.

By lessening the depth of the foundation and reducing the thickness of the planks, the expense is considerably reduced and, under the conditions mentioned, the efficiency of the building maintained.

The roof is composed of 3-inch planks, 6 inches wide, with a groove in each edge, and joined by a separate spline, and should be 20 feet long, so as to reach over two spaces between rafters. They should break joints every six planks. Upon these planks is laid either heavy roofing paper, mopped with tar, and then thick roofing tin, or three thicknesses of roofing felt, then coated with hot tar and covered with clean gravel in the usual manner.

No gutters are necessary, the water dripping from the eaves being caught by a strip of concrete 2 feet wide all around the foundation and inclining about 2 inches. This not only takes the water from the roof, but protects the foundation from surface water.

When the building is so located, from its position with reference to other buildings, or to a yard where work is being carried on, that it is not advisable to run roof water off on the ground, gutters may be formed of tin, or better, of galvanized iron, with proper connecting pipes to carry off the water. If the gutters are formed of the roofing felt, tar, and gravel, they will have to be of rather flat sides in order to prevent the tar from running down the conductor pipes when melted by the hot summer weather.

The windows of the monitor roof may be set singly, say 3 feet wide, between the uprights supporting the roof, or they may be made with double sashes in one frame, giving two windows, 3 feet wide each. The top sash should be hung on pivots so as to be opened for ventilation. Ribbed glass will be preferable for these windows, to avoid the glaring light which plain glass would admit upon the erecting floor under the traveling crane.

The side windows may be of two or three sashes, preferably three, the upper sash pivoted and the other two sliding sashes. Ribbed glass should be used in all but the bottom sash, which will very much improve the cheerfulness of the shop by being of clear glass.

The side window frames may be made of the form shown in the back wall, the upper portion being hinged or pivoted for ventilation, and the lower portion divided into two sashes on each side; but the dark shadow cast by the center upright in a double window frame is avoided if we make the window wider and employ a single sash in width.

As will be readily seen, the entire building is designed and constructed with a view of producing a practical, efficient, and commodious structure and one that will be, at the same time, as well adapted to the special uses and purposes for which it is intended as many buildings which are much more elaborate and costly; and still to so construct it as to make it a typical example of slow-burning construction.

CHAPTER VIII

SAW-TOOTH CONSTRUCTION OF ROOFS

The newest form of shop roof. Appearance and symmetry sacrificed to utility. Perfect illumination. Broad buildings may be properly lighted. Preferable for large areas. Economy of heating buildings with this form of roof. Roof angles. Roof construction. Steel and wood. Example of this form of building. Side walls. A high central space. Materials used in the construction. General design. Traveling cranes. Auxiliary cranes. Distribution of power for traveling cranes. The electric system. Roof trusses of steel. Roof trusses of wood. Ventilating windows. Ribbed glass. Roof planking on steel trusses. Roof planking on wood trusses. Gutters and valleys. Conductor pipes. Economical construction.

ONE of the most important advances in the design of machine shops and manufacturing buildings of the past few years is what is generally known as the "saw-tooth" construction of roofs.

Appearance, uniformity, and symmetry, are sacrificed to the idea of practical usefulness; the principal object being to secure as perfect and equal illumination as possible over the entire floor, whether the buildings are large or small.

and

Heretofore this has been one of the difficulties not entirely overcome, in consequence of this drawback it has not been possible to construct buildings beyond a certain width, owing, in this respect, to the dark zone along the center. With this new method of lighting we may practically make them as wide as we please and be assured that the central portion is, for all practical purposes, as well lighted as near the side walls. This is a great advantage in buildings in which large and heavy machinery is to be constructed, as this class of work may be much more economically built in shops having but one story; and as the earth furnishes the best foundation for a floor for heavy weights, this is desirable on that account. By this observation it is not meant, of course, that floors are to be laid directly upon the ground.

Again, for this class of work a large area is needed, and to construct comparatively narrow buildings in order that we may have the center of the room well lighted, is expensive as well as inconvenient in moving large machines, or in working around them.

By this method of construction the buildings may be very broad and

low and consequently easy to heat, and, as has been said, with good illumination over the entire floor.

The essential feature of the saw-tooth construction consists in forming the roof in broken sections, the roof proper having an inclination of about fifteen degrees, and the glazed portions an inclination of about sixty degrees.

Fig. 16 is a longitudinal section and Fig. 17 a transverse or cross-section of a machine shop with this type of roof, the construction being of steel. Fig. 18 and Fig. 19 represent a similar roof with wood used in its construction instead of steel. In Fig. 20 is given a perspective view of the machine shop when finished, showing the general arrangement of the high central portion and the lower portions at each side.

The side walls are built in the usual manner, with pilasters to strengthen them. They are pierced for windows on the same general plan as in the previously described buildings.

The plan of the building is the well-known one wherein a high central space is provided for an erecting floor, over which a heavy traveling crane is mounted, covering every part of this floor. The sides of this building, where it reaches above the side portions, may be planked up and covered with tarred paper and then tin, or, still better, with the specially stamped sheet steel. Corrugated steel or iron is sometimes used. Either of these plans will answer the purpose.

The side portions are built considerably lower as the same height is not here necessary or desirable. These portions are provided with smaller trav eling cranes, running upon I-beams or girders which project into the central space, as shown in Fig. 17, so that these cranes are capable of depositing their loads within the reach of, and under, the main crane.

If much heavy work is to be done, each of the bays, on both sides of the central portion, is supplied with one of these cranes, as shown in Fig. 16 and Fig. 17. By this means any load may be quickly and conveniently transferred from any one point, within any one of the bays to any point within any other bay, or to any point in the central erecting space, by the combined use of the main and secondary cranes.

may

In many cases it will be necessary to have these secondary cranes on one side only of the central space, the other side portion being reserved for machines and work of a lighter description. So, also, it may not be necessary to equip all the bays on one side, even, with secondary cranes, while it be necessary, and very convenient, to so equip several bays in this way. The nature of the work may be such that it will be convenient to equip several bays on each side and at one end with secondary cranes so as to arrange all the heavy work across the end of the shop instead of along the side.

As a matter of course, if traveling cranes are to be used over the bays