HOW TO DESIGN TERRACE OR ROOF GUTTER SIZE Designing the size of roof gutters involves considering factors such as the roof area, rainfall intensity, and local building codes. Here's a general guide to help you determine the appropriate size for roof gutters: 1. Calculate Roof Area: • Measure the length and width of each section of the roof. • Multiply the length by the width to get the area of each section. • Add up the areas of all sections to get the total roof area. 2. Determine Rainfall Intensity: • Check local weather data or use rainfall intensity maps to determine the average rainfall in your area. • Rainfall intensity is typically measured in inches per hour. 3. Consider Roof Pitch: • Steeper roofs may require larger gutters to handle the faster flow of water. 4. Use the Rainfall Rate Formula: • The rainfall rate formula is: Q=CiA where: • Q is the flow rate (in cubic feet per second or gallons per minute), • C is the coefficient of runoff (a dimensionless factor based on roof slope, typically ranging from 0.8 to 1.0), • i is the rainfall intensity (in inches per hour), • A is the roof area (in square feet). 5. Choose Gutter Size: • Once you have the calculated flow rate, you can choose a gutter size that can handle that flow. • Standard gutter sizes are often expressed in terms of inches, such as 5 inches or 6 inches. 6. Check Local Building Codes: • Be sure to check local building codes and regulations, as they may specify minimum requirements for gutter size based on factors like roof area and rainfall. 7. Consider Downspout Size: • The downspouts should be sized to handle the volume of water flowing from the gutters. Ensure that the downspout size complements the gutter size.