RIBBED SEAM METHOD

(Illustrated on Plate 1)

   The proper size and spacing of the ribs, or battens, depends on the design of the roof. They are preferably made of cypress, though spruce and North Carolina pine are commonly used. They are usually 2 inches square in section, with sides beveled about    ⅛ inch, firmly secured to the roof sheathing. Provision should be made in the carpenter specification for these ribs.

   The width of the sheet is dependent upon the spacing and size of the ribs. Copper sheets are stocked in widths in multiples of 2 inches, and the spacing of the ribs should be worked out to fit these widths. Example: If the rib is 2 inches by 2 inches and a spacing of ribs 21 inches, center to center, is desired, the width of the sheet necessary is 21 - 2 (width of one rib) + 2 + 2 (turn-up of sheet against sides of ribs) + ½ + ½ (allowances for locks) = 24 inches.

   Copper sheets of required width and standard length (96 inches), tinned on the crosswise edges, are laid on the roof between the ribs; the edges of the long dimensions are turned up at right angles to the sheet and are again turned at the top of the vertical leg parallel to and away from the ribs.

   These sheets are held in place by copper cleats, spaced at intervals of 8 inches and attached to the top and sides of the wood rib with copper nails, the free ends of the cleats being turned over to engage the edges of the sheets.

   The wood rib is then covered with a copper cap of proper width. The edges of this cap engage the edges of the sheets to form half-inch locked seams. At the cross seams the sheets are held in place by soldered locked seams, as in any other form of metallic roofing of this description.

   On steep slopes (15 degrees or more) soldered cross seams are not necessary, and the tinning of the crosswise edges can be omitted.

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