The most substantial form. Clearly shown in the engraving. Strength necessary. Vibration. Dimensions of timbers. Dimensions of walls. Wall plates. Dimensions of supporting posts. Special construction of floors. Dimensions of floor timbers. Roof construction. Gutters not necessary. Conductors. Windows. Application of gutters to buildings of over two stories in height. Nominal dimensions given.

The most substantial method of erecting a building of the slow-burning type of construction is with brick walls, properly strengthened by pilasters, or buttresses, and the interior work, floors, and roof composed almost entirely of substantial timbers and 3-inch matched planks.

This form of construction is shown in isometrical perspective in Fig. 11. The vertical section of the walls is made through the pilasters, between the windows, the thickness of the walls of the panels being according to their height and width. In this case only two floors are shown, but any reasonable height may be constructed in the same manner, provided that the walls of the lower floors are thickened according to the height, and that the central supporting posts are proportionately larger for the lower floors.

Consideration should also be given to the strength necessary to support any unusually heavy machinery that is to be placed on the lower floors.

As the height of the building is increased, the question of vibration becomes more important and additional strength of walls and timbers must be provided to meet it.

For a building of three floors the walls would be about as follows: For light work and no machinery to cause vibration, 16 inches for the first story, 12 inches for the second story, and 8 inches for the third story. For a building for heavier work, and where light machinery is to be used, these figures would be 20, 16, and 12 inches respectively. For higher buildings of say four stories, for light factory work, we may build the first-story walls 24 inches, the second-story 20 inches, the third-story 16 inches, and the fourth-story 12 inches. These should, of course, be strengthened by pilasters in the usual manner.

In all cases where the building is much beyond the usual width, the walls of the top story should not be less than 12 inches thick.

The pilasters should be about 50 per cent thicker at the base than the wall of the first story, and about 50 per cent thicker than the wall of the top story at a point two thirds of the height of the windows. Between these two points it tapers in a straight line, or has a regular "batter." From this upper point it is gradually thickened till at the top it is double the thickness of the wall. While these proportions are nominal, they are very nearly in accord with the regular practice. Upon these pilasters the floor timbers and the rafters have their bearing.

The walls are built to form bays of 8 feet centers. The floor timbers are beveled off at the ends as shown, where they enter the walls, and rest on cast iron wall plates, one of which is shown on an enlarged scale in Fig. 12. Their inner ends are carried by wooden posts, each of which are cut to the length which the height of the story is to be "in the clear," the space occupied by the floor timbers being taken up by cast iron "pintles" located as shown in Fig. 11, and of the form shown on an enlarged scale in Fig. 13.

By this method the supporting posts will not be disturbed by the burning away of a floor timber, even though it falls and carries a portion of the floor with it.

These posts should be of decreasing dimensions as they go up. For instance, if it is necessary to have them 12×12 inches on the first floor, those of the second floor will be 10 × 10 inches, those of the third floor 8×8 inches, and those of the fourth floor 6×6 inches, assuming, of course, that the weights of stock and material are much lighter on the upper floors, and no machinery employed on the two upper floors. Otherwise the posts should not be less than 8×8 inches on the top floor, and increasing in the above proportion on the other floors.

The floors are formed of 3-inch planks, whose lengths may be 16 or 24 feet, and which should break joints every three feet. As a matter of economy, these planks should be grooved on both edges and have tongues of a separate piece of wood introduced. The planks should not be over 6 inches wide.

Upon this floor is laid three thicknesses of rosin-sized paper, each layer being mopped with tar, rendering the floor water-proof. Upon this paper is laid a top floor of 1¬-inch hard wood, which may be at any time renewed when it becomes worn out, without disturbing the stability of the structure.

The floor timbers may be, say, 12 × 14 inches for a span of twenty feet between supports. Compound beams composed of two 6 x 14 inch timbers may be used instead of solid timbers, and in some respects will be preferable, as has been pointed out in a previous chapter.

The dimensions of floor timbers may also be decreased in the higher floors, but not to the same extent as the supporting posts are. Their depth must, of course, have reference to their length, which is constant, as well as to the lighter loads which they are to support.

The edges of the floor planks should be kept clear of the face of the walls by a space of about half an inch, as a safeguard against the expansion of the planks during damp weather. These spaces should be covered by light battens, both above and on the under side.

The hard wood top floor may be laid at right angles with the 3-inch plank, or diagonally, if it is desired to give greater stability to the structure. If these are laid diagonally, those of each succeeding floor should be at right angles with those on the next floor below, thus forming very efficient bracing in two directions.

The roof timbers may be 10 × 12 inches, and have a pitch of one-half inch to a foot. The roof is composed of 3-inch planks, the same as the floors, and covered with three thicknesses of roofing felt, and over this with tar and gravel, in the usual manner. If preferred, heavy roofing paper may be put on, then mopped with tar and heavy roofing tin used. The roofing paper under the tin will prevent the difficulty of condensation.

The rafters should be fastened at the outer ends by vertical bolts anchored in the walls, and by ¾-inch iron dogs where they meet in the center. Ordinarily it is not necessary to have a supporting post in the center where they are joined together.

There need be no gutters on this style of roof, as a sloping concrete strip 2 feet wide laid around the building, and closely against the foundation wall, will answer the purpose of carrying off the water from the roof as well as protecting the wall from saturation by surface water. However, gutters may be added, and in some later examples are so arranged as to hold the water from flowing over the eaves and pass it along to conductor pipes running down inside the building so as to be safe from the liability of freezing up in winter. These gutters are more readily applied to roofs covered with tin than to gravel roofs, owing to the difficulty of making a water-tight joint between gravel and tin and, also, the liability of the tar on a gravel roof melting and running down the sides of the gutter and into the conductor pipes, if the sides of the gutter are formed of tar and gravel, the same as the roof.

For buildings of over two stories it is advisable to have gutters, as it is also where the building forms one side of a much used yard or driveway, where the dripping water, liable to be blown about by the wind, would make it very objectionable.

The windows will be constructed in the manner described for windows generally, in the chapter on lighting, to which the reader is referred. It will be understood that the figures herein given for walls and beams are nominal, and that in each individual case they must be of such dimensions as are called for by the loads and strains they will have to sustain, the vibration to which they will be subjected, and the height of the building.