Copper Flashings - A Manual - 1925 - Page 48
TABLE I (Continued)
Approximate Weight of Sheet Copper per Square Foot in Fractional Parts of an Inch
1/16 inch thick weighs 3 pounds to the square foot
1/8 inch thick weighs 6 pounds to the square foot
1/4 inch thick weighs 12 pounds to the square foot
1/2 inch thick weighs 24 pounds to the square foot
1 inch thick weighs 46½ pounds to the square foot
To Ascertain the Weight of Copper. – Find the number of cubic inches in the piece, multiply by 0.3214, and the product will be the weight in pounds. Or, multiply the length and breadth (in feet) and that by the pounds per square foot.
These weights are theoretically correct, but variations must be expected in practice.
The use of crimped copper is well-established, and on the best work it is recommended.
Crimped sheets can be obtained from any of the large mills by special arrangement. Many of the larger roofing firms are also equipped to do this work.
The crimps consist of 3/16 inch V-shaped corrugations running cross-wise with the length of the sheet.
Crimping is expensive. It reduces the size of the sheet, and there is, of course, a charge for the labor involved. The process tends to harden the copper. The amount of hardening is, however, not great.
Its chief advantage is in its behavior under temperature changes. The crimps make splendid expansion joints. For this reason its use in large built-in gutters, where fastenings are difficult to make and small sheets are inadvisable, is well worth consideration.
Crimped copper is extensively used for cornice work both for ornamental and practical reasons. It gives a nice finish to the plane surfaces of the cornice and the crimps allow opportunity for expansion and contraction.
SIZE OF SHEETS FOR GUTTERS
Small sheets are generally used for lining gutters and decks, pans, etc. Large sheets are more difficult to handle than are small ones. Because they are closer together and there is only a small amount of cumulative expansion, the strain on the seams and cleats is minimized by the use of the small sizes.
When small sheets are used more seams and more labor is necessary. This is the one objection to their use. A method of strengthening the seams of long sheets used in gutter-linings has been used successfully. It is recommended for gutters generally, and particularly in masonry work where the setting of wood nailing-pieces for small sheets means a considerable expense. The ends of the long sheet, which are laid the long way of the gutter, are flat or double-locked to 4-inch strips laid across the gutter. The two seams thus formed are fastened with cleats to one nailing piece.
The length of any sheet or strip should not exceed 8 feet. The width depends upon the type of flashing. In general, decks, crickets, and similar large flat spaces on roofs are covered with small sheets, about 18 inches by 24 inches, or 20 inches by 30 inches. The size of sheets used in gutter-linings depends largely upon the design of the gutter. There is no hard and fast rule.
BUILT-IN OR BOX GUTTER LININGS
For best results in gutter-linings the following practice is recommended.
(1) The design of the gutter should avoid sharp angles. The sides should slope as much as possible to approximate an arc. The inside edge of gutter should be at least 3 inches higher than the outside edge. Gutters should be as shallow as possible.
(2) The gutter should be wood-lined to receive the copper.
(3) Sixteen-ounce soft (R. T.) copper sheets which have been crimped are excellent. Their length is optional up to 8 feet maximum; their width should not exceed 36 inches.
(4) Longitudinal seams should be double-locked. This provides strength at the seam and with (3) allows plenty of opportunity for expansion.
(5) Seams should be well-soldered.
(6) The junction with the roof flashing should be by a large loose-locked joint so placed as to need no solder to make it water-tight.
(7) If long sheets are used a double-cross seam should be used. The construction of this is described above.
INNER-LININGS FOR MOLDED GUTTERS
In long runs of molded gutters (such as is shown in Fig. 93, page 63) it is sometimes necessary to install false bottoms, or inner-linings, in order to get the proper slope to the outlet. This
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