Copper Flashings - A Manual - 1925 - Page 59
Progressive Steps in Designing Gutters and Leaders:
1. Locate position of leaders.
2. Compute area of roof drained by each leader.
3. Compute size of leader by dividing roof area by 150.
4. Compute size of gutters to supply leaders.
1. Round leaders should not be less than 3 inches in diameter.
2. Rectangular leaders should not be smaller than l¾" x 2¼". (This is commonly called "2" square inches).
3. Gutters should not be less than 4 inches wide.
4. Gutters should have a fall of not less than 1 inch in 16 feet.
5. Scuppers should be provided for all roofs with a parapet wall built around them. This precaution prevents an overloading of the roof due to stoppage of the outlet.
6. All outlets should be provided with screens or strainers.
[This Association, being engaged solely in research and educational work, and being in no sense a selling organization, does not quote prices.]
In the tables and text of this handbook, where a base price, or list price, is set out, this price is derived from an average selling price for copper and cost of manufacture and distribution. Market conditions raising or lowering the selling price of copper, or affecting to a very appreciable extent the cost of manufacture, would raise or lower this price. The tables of extras are derived from printed lists in public use at the time of publication.
In using this handbook for the purposes of estimating, the base price, list price, table of extras and discount on extras, at the time of estimate, should be obtained, so far as necessary, from a reliable manufacturer or dealer. Any unusual variations from the method of computation set forth herein should be investigated by the person making the estimate.
In using the tables of list prices it should be borne in mind that these prices are subject to discount. When making up cost data the market discounts from list should be obtained.
ESTIMATING THE COST OF COPPER SHEETS
The difference in the cost of copper sheets is determined by (1) the thickness, (2) width, and (3) length. Sheets can be obtained of any desired dimension as shown in Table III. Table IV gives the extras added to the prices in Table III for various items such as tinning and polishing. It will be noted that hard (C. T.) sheets carry an extra.
Examples of the method of computing follow:
I. What is the price of 16 oz. soft (R.T.) sheet copper 30” x 96”?
The base price of soft (R.T.) Copper sheet is assumed at 23¾ cents per lb. and there is a 10% discount on extras.
From Table III the extra for sheet over 28" to and including 36" in width and over 72" to 96" in length is 2½ cents per lb. Deducting 10% makes this figure 2.25 cents. Adding to the base we get
Base. . .23.75 cents
Extras. . 2.25 cents
Total. . . 26 cents per lb. (or square foot)
II. What is the price per sheet of hard (C.T.) 18 oz. copper 14" x 20", tinned 1" wide on the edges?
The extra for 18 oz. soft (R.T.) sheet 14" x 20", is 2.5 cents per lb. (Table III.)
The extra for hard (C.T.) sheets is 3.0 cents per lb. (Table IV.) For tinning hard (C.T.) sheets there is an additional extra of ½ cent per lb. (Table IV.)
+ 3.0 cents
+ 0.5 cents
= 6.0 cents
-0.6 (less 10% discount)
= 5.4 (Net extras)
The base price for copper sheets is assumed at 23.75 cents per lb. Price for hard (C.T.) sheets, 14" x 20", is 23.75 + 5.4 = 29.15 cents per lb.
A sheet 14” x 20" contains 1.94 sq. ft. At 18 ozs. per sq. ft. the sheet weighs 2.18 lbs.
Tinning is figured as so much per square foot of sheet tinned without regard to the actual area tinned.
- 59 -