straight up to bear the weight of the column above, while the girder is borne by the projections cast upon the column. The distance from the cap to the top of the column should be about four inches greater than the depth of the girder to give room for bolting the columns together.

With a wooden girder, the ends of the timber must be cut out to fit the diameter of the column, Fig. 209, and the girders must be tied across the cap by stout straps on each side. If steel beams are used, they can be tapped to the column plate or strapped together around the column.

Pipe Columns. Heavy wrought-iron pipe is often used for columns, a cap and base being sometimes cast and screwed on by a thread; and a patented column, formed

Fig. 208. Proper Application of Ornament to Column

by filling the pipe with cement, may be obtained ready-fitted with cap and base.

Wooden Girders. If wooden girders are used, they may be set wholly or partially below the floor timbers, or flush with them.

Girders below Floor Timbers. If there are no objections to dropping the girders below, this is the simplest and strongest construction. In this case, the floor beams should be sized down on the girders to maintain a perfectly level floor line, and a full bearing should be obtained for each timber. Where the girders are large, the timbers may be brought to butt against each other upon the girder; and they should be secured end to end by iron dogs which

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Fig. 209. Method of Seating Girders on Column

turn down into each timber, Fig. 210. For small girders and light timbers, it is better to let the timbers lap close and be spiked to each other, as in Fig. 211.

When the girders are near together, and the timbers long enough to span two divisions, a rigid floor may be obtained by breaking joints with the floor timbers every five or six feet.

Girders Flush with Floor Timbers. If the girders are to be framed flush with the timbers, the use of stirrup irons or patent hangers is recommended, as

preserving the full strength of the girders. In this case the

Fig. 210.

Use of Iron Dog to
Connect Large Girders

Fig. 211. Spiking of Joists

timbers on each side of the girder should be brought opposite one another as nearly as possible, and iron dogs long enough to reach over the girder and drive down into opposite timbers should be used, Fig. 212.

If the girder is deeper than the floor timbers, it may be set flush on top, and smaller pieces of hard pine or an angle iron may be bolted to the lower part of the girder in order to support the floor timbers, as shown in Fig. 213.

Fig. 212. Use of Patent Hangers for
Joists Flush with Girders

Fig. 213. Method of Making Joists Flush with Girders

Steel Girders. Where the spacing of columns has to be increased beyond the safe bearing of wooden girders, steel girders may be used. These usually consist of one or more steel I-beams, and they may be used with cast-iron columns or with steel columns. With cast-iron columns, the same methods will suffice as are used

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Fig. 214. Use of Stirrup Iron with
Steel Girders

for wooden girders, but with steel columns a different method of construction is necessary, which it will be better to consider later in connection with steel framing. It may be properly said here, however, that the use of steel girders and steel columns, even if the floor timbers are of wood, is to be recommended for high buildings and for buildings which are subjected to the jar of machinery. The reason for this lies in the greater rigidity which is possible in the girder and column connections, and the greater ease of bracing this construction. With the use of steel girders new considerations arise. If a single girder is set entirely below the floor timbers, it will give a better bearing if the timbers lap and spike to each other. With two or more girders, the timbers may be brought end to end as on the heavy wooden girder. If the steel girder is set flush with the timbers, the latter may be cut so as to run into the trough formed by the flanges of the girder, but they should be supported by stirrup irons or hangers, Fig. 214, as the sloping flange of the steel girder does not afford a good bearing. If the steel girder is deeper than the floor timbers, a common method is to bolt a timber to each side for a bearing; an angle bar can, of course, be used in the same manner, Fig. 215. In any case, the floor beam should be fastened so that there is no danger of slipping out of the hanger. Most of the patent hangers have a lug, or bolt, to secure the timber in place, and where timbers come opposite to

one another, common iron dogs turning down into each timber may be used. Crowning of Floor Timbers. All floor timbers having a span of more than 16 feet should

Fig. 215. Fastening Wood Joists to Steel Girders
Using Wood Bearing Timbers or Angle Pieces

span.

be crowned, that is, the top of the joist should be cut to the shape of an arc of a circle, having a rise of inch to every 16 feet of This is necessary to allow for the ordinary sag of the timber, so that a level floor will result.

Supervision of Floor Framing. The supervision of the framing of floors of brick buildings calls for constant vigilance on the part of the superintendent. Not only is it necessary to follow closely the work of the carpenters, but the fact that the mason work is being carried along at the same time by a different set of workmen demands a great deal of forethought in order to bring the different parts together at the right time. The anchoring of floors properly, and at the proper time, requires constant attention, and the setting of plates, the building-in of bolts and hangers, and the leveling-up of floors and walls to their relative positions necessitates harmonious action between mason and carpenter.

In heavy framing, careful watching is essential to see that all necessary connections are made between post, girders, and floor beams, and that ties, straps, and bolts are set and tightened. If trusses occur, they should be strained up tightly when built, and kept tightly strained as long as there are any workmen remaining at the building, as the shrinkage of the timbers often loosens the joints and allows sagging to occur.

SLOW-BURNING AND MILL CONSTRUCTION

Slow-Burning Construction. The methods of heavy timbering recently described, with floors of matched or splined plank, and with no wood partitions or furrings enclosing hollow spaces, constitutes what is generally termed slow-burning construction. To obtain the best results from this method of construction, wooden girders should always be set flush with the floor timbers on top, as the dropped girder with the space above will permit flames to lap around the timber so that it will be more quickly consumed than if it is flush with the rest of the floor beams. Greater protection is obtained by covering the wood with plaster on metal laths, leaving no air spaces between the plaster and the wood.

Mill Construction. As its name indicates, mill construction belongs to the particular methods of building which have been devised for resisting fire and for sustaining the loads and shocks of machinery to which manufacturing structures are particularly subjected. This requires primarily the disposition of the timber and plank in solid masses, so that the fewest number of corners will be exposed to the action of fire, the separation of floors by fireproof

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stops, automatic arrangements for closing hatchways and elevator openings, and incombustible partitions for enclosing stairways.

Beams. The typical construction employed for the mills of New England, and the only form acceptable to the insurance companies of that section, calls for posts at least 10x10 inches, spaced about 8 feet apart in the length of the mill and 24 or 25 feet across. Instead of a line of girders running lengthwise over the line of posts, the floor beams are laid across the mill on the top of the posts. These beams are usually 12X14 inches, or in two pieces each 6×14 inches, bolted together with an air space between. The wall ends should rest on iron plates, and the ends should be beveled off and secured only at the bottom, so that they may fall out easily if burned and not pull down the wall, Fig. 216. These beams

are supported by iron post caps or pintles, as already described.

Flooring. The flooring consists of a layer of 3-inch planks not more than 10 inches wide, splined together and blind-nailed; it should be long enough to span two spaces, breaking joints every 4 or 5 feet. All of this construction is usually of Georgia pine.

The upper floor is generally made of hardwood, such as maple or birch, and this Fig. 216. Effect on Brick Wall

is laid with square edges over two or three thicknesses of paper, each layer being mopped with tar, asphalt, or some similar material; sometimes a layer of plaster is spread between the upper and under floors.

Partitions. Where slow-burning or mill construction is used for the floors of a building, the partitions should be made of solid plank, plastered on both sides on metal lathing, or else of light steel framing with metal lath and plaster.

Roofs. The same methods of framing may be employed for the roofs as for the floors, but lighter timbers can be used, set to the required pitch, with a tar and gravel or metal roof. Sharply pitched roofs may also be constructed in the same way, the timbers being trussed if the span requires it.

Adaptation to Mercantile Buildings. This style of construction may be adapted to the use of mercantile or office buildings, but the