|
|||
STEPS FOR SELECTING PROPER ROOF DRAIN LEADER SIZES AND NUMBER REQUIRES FOR A GIVEN ROOF |
|||
| Steps: | Example: | ||
| 1. Calculate the total roof area. | 1. Total roof area - 500' by 270' equals 135,000 sq. ft. | ||
| 2. Determine the maximum hourly rainfall in inches. (The figure can be acquired from your local weather bureau and/or local code authority.) | 2. Determine rate of rainfall - for this example use 4". | ||
| 3. Select leader size. | 3. After studying building plan and physical arrangement, assume that 6" leaders are required for this job. | ||
| 4. From Table 1, determine the number of square feet that can be drained by one roof leader at the local maximum rainfall rate. | 4. From Table 1 - one 6" leader at 4" rate of rainfall will take care 13,500 sq. ft. of roof area. | ||
|
5. Divide the total roof area by the area that one leader will handle.
The above result is the number of roof drains required for the building. If the result is a fraction less, use the next higher number. |
5. Number of roof leaders required is 10 (135,000 sq. ft. divided 13,500 sq. ft.), thus 10 roof drains would be required. | ||
| NOTE: It can readily be seen that if 4" leaders were used, the number of roof drains required would increase to 30 drains. (29.348 rounded off to next highest number.) If a smaller number of roof drains are required, then larger leaders would have to be chosen. Several small drains and leaders rather than one or two large drains will insure even safer yet adequate roof drainage. Drains should be spaced for uniform drainage. | |||
|
ROOF DRAIN VERTICAL LEADER REQUIREMENTS FOR HORIZONTAL ROOF AREAS AT VARIOUS RAINFALL RATES | |||
|
TABLE 1 | |||
|
| |||
|
Related Links: | |||
 |
 |
 |
 |
To select the proper roof drain, the following information must be
determined by the specifier.