Trusses for Flat Roof

TRUSSES FOR FLAT ROOF. A carpenter recently had a typical flat-roof store building to erect.

Fig. 176. Cheap Lattice Truss.

It was to be 44 feet wide and 100 feet long, the roof to slope from front to rear and to be cov ered with gravel roofing. The building was two stories high, one room on each floor. The fol lowing advice was asked: "How would you frame roof without having columns under second-story ceiling? Second floor is to be used for skating rink. How would you deaden floor? Joists are to be 2 by 12-inch hard pine." The best way to carry such a roof is by a series of trusses, as shown in Fig. 177. The heights of these trusses vary according to their position, a fall of 1 inch to the foot being allowed for the slope of the roof. The truss shown in elevation in Fig. ].78 is the lowest of the series; but the rest would be similar in all respects.

It is difficult to deaden a floor effectively when used for such a noisy purpose as roller skating; but we advise a double deadening as most likely to fill the bill. One method, shown

in Fig. 179, consists in nailing strips near the lower edges of joists to support short lengths of boards, upon which is laid a rough mortar either of sand and lime, ashes and lime, or sawdust and lime. Or one of the special patent composi tions, such as slag wool, made for the purpose, might be used.

The second deadening is applied between the rough floor and the hardwood upper flooring, and consists of heavy deadening felt made for the purpose. In the case of a rink, the felt should be laid on the rough floor; then strips of 1 by 2-inch stuff laid flat, 12 inches apart; and then the hardwood floor laid to form the skating surface.