Fig. 11
As distinguishable from the reveal frame, there is the plank-frame construction, which is not built into the brickwork, but is built up as shown in [Fig. 11]. When it is desirable to have the central mullion a, [Fig. 9], as narrow as possible, the box construction indicated on the drawing is done away with and the window is hung by means of overhead pulleys, the weights operating in the boxes at the sides.
STANDARD SLOW-BURNING
CONSTRUCTION
30. A type of factory construction more usual than that previously described is illustrated in [Fig. 12]. In this illustration, it will be noticed that the main girders bear on wall pilasters, and the spandrel filling between the pilasters is kept as thin as possible. The usual reveal window frame is used, as shown at a, and the soffit of the arch over the window openings is checked at the head of the opening to provide a wind and water stop as at b. In this construction, which is probably the best, though it does not possess the advantage of giving the maximum amount of window space, and, consequently, light in the building, a rowlock or bonded brick arch is used over the window frames. By means of this construction, either the window frame may be built in place, or the windows may be slipped in from the back against a rabbet formed in the brickwork. The arch over the window head is indicated at c.
Fig. 12
Fig. 13
31. Floor Construction.—The floor construction consists of heavy timber girders, no dimension of which may be less than 6 inches, as otherwise it would not comply with the requirements of slow-burning construction. The floor planking consists of 3- or 4-inch tongued-and-grooved spruce, or yellow-pine planking, planed on the under side, and thoroughly spiked to the girder. Planking of the former thickness may be used for clear spans as great as 8 feet, while the latter thickness may be used for up to 10-foot or even 12-foot spans, if the loads are light. The girders are indicated at d, and the floor planking at e. Usually the girders, in order to obtain the requisite strength, are made of long-leaf yellow pine. On the top of the spruce planking is placed a finished maple floor. This floor is made from either 1-inch maple, which finishes as ⅞ inch, or 1¼-inch maple, which finishes as 1⅛ inches, in thickness. Neponsett sheathing paper, or deadening felt, is placed between the spruce planking and the finished maple flooring for the purpose of preventing dust from percolating through. This sheathing paper or felt is sometimes made waterproof to prevent leakage due to water used for fire-extinguishing purposes.
Frequently, the brickwork is corbeled out, as indicated at f, in order to form a fire-stop between floors, or at least to prevent an open joint at this place. Where the walls are offsetted, as shown in [Fig. 13], there is no need of corbeling out, for the offset in the brickwork can be made to form the fire or dust stop.