Joists should be bridged. [Fig. 55] shows the more common method of bridging. The joists may be 2 × 8 in small, inexpensive houses, and 2 × 10 or 2 × 12 in large ones, bridged once in a 12-foot span, twice in a 16-, and three times in an 18- or 20-foot span. The bridging is of the utmost importance and should never be omitted, as it serves to strengthen the floor joints and prevents the disagreeable trembling of the floors so annoying in many of the older houses.
Fig. 55. Bridging the joists.
The studding for a balloon frame is either 2 × 4, 2 × 5 or 2 × 6, and the length desired. The 2 × 4 studding are too light for an ample two-story house, and they do not give enough thickness of wall for the most desirable window- and door-jambs. The doors are not held firmly in place, and when they are closed quickly by the wind or by children, the plastering is injured. Studding 5 inches broad, fortified by outside diagonal boarding ([Fig. 56]), gives the ideal conditions unless the house is unusually large, in which case the studding should be 6 inches broad. The diagonal boarding costs a trifle more in material and labor than the horizontal, but it is so much superior that the extra expense may well be incurred. Every board forms a double brace, one where nailed to the studding and one where the siding or “clap boards” are nailed to the rough boards and the studs. Nothing has yet been discovered which is so satisfactory, and which gives such strength and protection to the frame as does this preliminary diagonal boarding, covered with paper. When completed it forms a wall open enough to prevent dry rot and tight enough to prevent the entrance of wind.
Fig. 56. A wall strengthened by diagonal sheathing.
The second-story joists rest on stringers or light girders 1 × 5 inches, as shown in [Fig. 57]. If the girder is set flush with the inside of the stud, A, the laths must lie directly upon the face of the girt. This gives no room for the mortar to form clinches behind the lath. This 5-inch girder swells when the mortar is put on and shrinks when it dries, which may result in a crack in the wall in the angle near A. Since, by reason of faulty construction, there are no clinches behind the lath, the plastering becomes loosened, and this is likely to be the beginning of serious trouble. If the girder is let in so that its face is not flush with the inside of the stud and then furrowed out with small pieces of lath, the effects of the shrinking of the girder will be obviated and room will be left for clinches behind the lath.
Fig. 57. Second-story joist.
In windy, cold climates, where lumber is at all abundant, a second boarding may be placed inside, covered with paper and furrowed out with a single thickness of lath to allow, as in the former case, the formation of clinches. There is no objection to boarding horizontally on the inside, if the outside has been boarded diagonally. The term “rough boarding” has been used, but it should be said that the boarding which forms the first covering, sometimes called sheathing, should be brought to uniform thickness and matched or rabbeted.