21. Loose-Locked Seams.    Where, on copper-covered surfaces, an intersection of roof planes, or an abrupt change of slope, shall occur, the joint between the flashings on the two surfaces shall be an unsoldered loose-locked seam similar to a standing seam hammered flat or a double lock seam. It shall be placed as close to the line of intersection as possible and shall be so formed as to preclude leakage. It shall not be fastened to the roof, except that at the cross seams of the sheets so joined cleats may be set close to the loose-locked seam.

22. Crimped Copper.    All copper sheets used for flashings, gutter-linings, etc., shall be crimped by passing through heavy rolls to form 3/16-inch ridges in the sheets in the direction of the short dimension.

23. Size of Sheets.    (-1.) Strip copper shall be used for all flashings up to 18 inches in width.

   (-2.) In general flashings for flat surfaces such as decks, crickets, etc., shall be of sheets not larger than 18 x 24 inches. Under special conditions larger sheets may be used with the approval of the architect.

   (-3.) All built-in and lined gutters shall be flashed with sheets of size specified under "Built-in Gutters."

24. Cleats and Fastenings.    All flashings over 12 inches wide shall be fastened by cleats 1½ inches wide and about 3 inches long, spaced as specified elsewhere. They shall be secured to the roof by two nails set about ¾ of an inch from the end and shall have the end turned back ½ inch over the nail heads. The free end of the cleat shall be turned over ½-inch to engage the edge of the sheet and shall be locked into the seam. Where seams are soldered cleats shall be tinned. Except as otherwise specified cleats shall be spaced not more than 12 inches apart. Where used with 18 x 24-inch sheets four cleats shall be used for each sheet.

   Flashings less than 12 inches wide shall be secured by nails spaced as specified for different types of flashings. Where flashings are nailed the nailing shall be restricted to one edge only. Nails shall be near the edge and shall be evenly spaced not more than 4 inches apart, unless otherwise specified.

25. Exposed Edges.    The exposed edges of all flashings shall be folded under ½ inch, in such manner as to conceal them from view.

26. Flashings - Where Required.    All intersections of roofs with vertical surfaces of every kind and all openings in roof surfaces, shall be flashed with copper. The method of flashing, except as otherwise shown or specified, shall be base and counter-, or cap, flashing.

27. Continuous Flashings.    Where the design or construction is such that the base and counter-flashing method is impracticable, flashings shall be made continuous from the roof surface up and into the vertical surface. Flashings of this type shall be made generally in two or more pieces, locked and soldered together. Where possible the joints shall be made by flat or double lock seams. Otherwise lap seams shall be used.

28. Base Flashings.    (-1.) Unless otherwise specified or shown on the drawings base flashings shall be, in general, at least 4 inches high, and shall project at least 4 inches out on to the roof. Flashings shall be full pieces 96 inches in length. On sloping roofs they shall lap longitudinally at least 3 inches. On flat roofs the joints shall be flat-locked and soldered.

   (-2.) Against stucco-coated walls, the metal lath shall lap outside the flashing so that the stucco shall finish over the flashing.

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