Rainfall Draining of Roof Areas and Vertical Downspouts
Capacities of vertical downspouts when draining roof areas in rainfall.
Capacities of clean vertical downspouts without obstructions when draining roof areas are indicated below:
| Downspouts Size | Roof Area | ||
|---|---|---|---|
| mm | inches | m2 | ft2 |
| 50 | 2 | 65 | 700 |
| 65 | 2 1/2 | 120 | 1300 |
| 80 | 3 | 205 | 2200 |
| 100 | 4 | 430 | 4600 |
| 150 | 6 | 1255 | 13500 |
The table is based on rainfall intensity 100 mm per hour (4 inches per hour). Rainfall intensity should always be checked with the local authorities.
Gutters and downspouts are vulnerable for obstructions caused branches and leafs from surrounding trees and similar. This should be considered when connecting gutters and downspouts.
