Rain Runoff From Roof

So a 50 x 20 roof is 600 x 240 multiply the roof dimensions by the number of inches of rainfall.

Rain runoff from roof.

The area we are calculating here is the same as if your roof were flat. A 1 000 square foot roof can produce more than 600 gallons 2 271 2 l of runoff for every 1 of rain that falls on it. If your downspouts are connected directly to a storm drain disconnecting them is the single most important step you can take to reduce runoff. If you have heavy runoff from roof downspouts and neighboring properties redirecting or capturing runoff can provide better control.

Step 2 multiply the area of your roof by the amount of rainfall you wish to calculate for. To calculate the runoff from any given rainfall. Even though most roofs are pitched at an angle the only part that will affect the rain runoff is the actual area underneath your roof. 1 place a piece of standard metal drip edge onto a table or between a pair of sawhorses.

However there is a way that you can redirect the rain off the roof so it falls harmlessly out of the way. Use the water that drains off your roof. Count the number of downspouts coming from your roof. In this example 600 x 240 x 1 144 000 cubic inches of water divide by 231 to get the number of gallons because 1 gallon 231 cubic inches.

Convert the percentage to a decimal by dividing the percentage by 100. The answer is about 623 gallons. These techniques will minimize the amount of water that accumulates or that causes erosion in the problem area.