Copper Flashings - A Manual - 1925 - Page 46
FLASHING OLD AND NEW WORK
Where a new building adjoins an old one it is necessary to flash properly the joint between the two so as to prevent water running down between them. The new wall may be higher, or lower, than the old, or the walls may be even. Methods of flashing will necessarily differ. It is necessary to provide a water-stop and allow for the settlement that is bound to occur.
A method of handling the three cases named is described in paragraph 79, page 41, of the specifications. The cap referred to in Alternate (-3) is that shown in Figs. 67, 69, and 70.
When conditions different from these are encountered special methods of flashing must be devised, keeping in mind the movement to be expected after the flashing has been done.
Wood sheathing is of great importance in flashing work. Green or wet boards shrink and warp and cause cracks and wrinkles in the metal covering. The ideal sheathing is of kiln-dried boards. These are, however, rather expensive. Satisfactory results can be had with stock boards provided allowance is made in laying for movement. After laying sheathing should be protected against rain, and no metal should be laid before the boards are thoroughly dried out.
Ship-lap is better than tongue-and-groove boards. It is easier to lay and there is practically no trouble from warping and swelling.
All boards should be well-nailed at every bearing and separated slightly to allow for the swelling that comes with dampness. All exposed nail heads should be sunk.
Under all flashings, in built-in gutters, etc., use building paper. Rosin-sized felt weighing about 6 pounds per 100 square feet is recommended. On narrow flashings, it is not absolutely necessary. Over rough surfaces, such as concrete, etc., it must be used as a protection against abrasion. When used with mason work, which is subject to discoloration, a black waterproof-paper should be used. (See page 45.)
For fireproof construction the National Board of Fire Underwriters recommends an asbestos-felt paper about one-sixteenth of an inch thick, weighing approximately fourteen pounds per hundred square feet.
"SOFT" AND "HARD" COPPER FOR FLASHINGS AND GUTTERS
Copper sheets are made in varying degrees of temper, or hardness. Experience has definitely established the two which are best suited for flashings and for gutters and leaders. The building profession has come to know these two as "soft-" or "hot-rolled,” and "hard-" or "cold-rolled" copper, and it is common practice to so designate the sheets in specifying or ordering.
It can be readily understood that because there are different degrees of temper mistakes often occur due to the confusion arising from ordering, for instance, "16-ounce hard-rolled copper." The question the manufacturer asks is "how hard"? for the process of manufacture is dependent upon the results desired.
Copper sheets are made from "cakes," which, after being heated to the required temperature, are passed through rolls until the desired thickness of sheet is obtained. The first part of the process is the same for all tempers. When the copper has cooled below a workable temperature, it is again heated and roiled, this procedure being carried on until the sheet is within a few gage numbers, or thicknesses, of the finished product.
If the material is to be "soft-" or "hot-rolled” it is again heated and rolled to the required thickness, and then given a final heat or "anneal" to remove the hardness acquired by rolling.
The hardness of sheets is determined by the reduction in thickness before reheating. So, depending upon the temper or degree of hardness desired, the sheets are brought to certain thicknesses which will give the required final thickness with the necessary rollings, are then heated to the proper temperature, and are finally rolled to the desired thickness — and hardness — and allowed to cool.
From the above process it is obvious that unless the temper, or hardness, is definitely specified, or the purpose for which the sheet is to be used is described, the manufacturer has not the information necessary to supply the proper material. As the result of the confused use of terms, sheets of a hardness ill-adapted to the service desired have sometimes been used, with disastrous effect.
As mentioned above there are two hardnesses of copper which are adapted to use for roofing purposes. The manufacturer knows from experience what these degrees of hardness are. They are designated as "roofing temper" and "cornice temper." The former is a "soft-" or "hot-rolled" product, the later a "hard-" or "cold-rolled" one.
In order to prevent misunderstanding and confusion, and to make as definite as possible the kind of copper desired, it is recommended that the
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