Regulating the Erection, Construction, Repair, Alteration, Location of all Electric Signs

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shall be made for the difference in expansion between the plastic and the frame. One- sixteenth (1116) inch total clearance for each twelve (12) inches or fraction thereof, of the dimension perpendicular to the mounted edge shall be provided in the mounting system. 5. When plastic is held in place by flanges, troughs, channels or clips, these means of attachment shall overlap the plastic by not less than three - eighths (3/8) inch for panels up to twelve (12).inches wide; for panels over twelve (12) inches wide and up to twenty -four (24) inches wide, seven six- teenth (7/16) inch; from twenty -four, (24) inches to thirty -six (36) inches wide, one half (J) inch; thirty -six (36) inches to forty -eight (48) inches wide, nine - sixteenth (9116) inch; and over forty -eight (48) inches, three fourths (3/4) inch. Flanges, troughs or continuous channels shall be made of galvanized sheet metal, copper or aluminum, not less than twenty (20) gauge U.S. standard in thickness, Where clips are used for attachment they shall be made of non - corrosive spring type material such as phosphor bronze or equivalent; the thickness of which shall not be less than .032" in thickness. Each clip shall not be less than two (2) inches wide and clips, bolts, screws or rivets shall be spaced on not less than seven (7) inch centers around the entire perifery of the plastic. 6. When bolts, screws or rivets are used to fasten plastic material to a metal frame, washers shall be placed under the heads of the bolts, screws or rivets. These washers shall be of metal of a non - corrosive material and have an outside diameter of not less than six (6) times the diameter of the screw being used. Washers to be not less than .032" in thickness. 7. Undue pressure of fastening devices against the plastic material should be avoided by use of suitable gasket material, spring tension, or adeq ate clearance to allow.for expansion. - 8 -