For most residential roofing systems around the country, five-inch gutters are enough to handle the amount of rainfall. But if your home is one of the biggest in your neighborhood or has a steep roof, then you may need wider gutters, more durable gutter guards and extra downspouts. This is especially true if your local climate is prone to heavy rainfall or severe storms.
When figuring out the right size for your gutters and downspouts, you first have to calculate the square footage of the gutter’s drainage area. A gable-ended roof, for instance, only needs a calculation for each of its two slopes. But most roofs have multiple facets, so you need to add each surface within a drainage area to get the total square footage needed. You can consult your trusted contractor to help you get the right measurements.
Pitch and Rainfall Adjustments
Next, you can proceed to adjust for your roof’s pitch. You can measure the pitch of your roof with a two-foot level and a tape measure by holding one end of the level against the roof, leveling it, and then measuring the distance between the roof and the underside of the level at its midpoint, which should give a 12-inch run. For instance, a 5-inch gap is a 5-in-12 pitch.
As you’re doing this, remember that a steep roof pitch tends to collect more rain when the rain is blown by the wind. You’ll also need to adjust for your area’s maximum rainfall intensity, which can be searched through the U.S. Weather Bureau records online. Make sure to look for the maximum rainfall that could possibly happen in a five-minute period, in inches per hour, in your region. The higher the amount, the bigger the gutter should be.
Determine the Size of Your Gutters
Multiply the drainage area by the roof-pitch factor and rainfall intensity to calculate the adjusted square footage. Afterward, use the chart below to see what size is needed for your roof. If the several drainage areas of your roof happen to have gutters in different sizes, it’s best to go for the biggest one.
Determine Whether You Need Extra Capacity
Make sure to get seven or eight-inch gutters if the runoff is not found in the chart for standard gutters. While they’ll likely cost more and require a custom order from a professional roofing contractor, it will help save you a lot of potential roof repair costs later on. Don’t forget to check whether your downspout’s capacity matches or exceeds the expected runoff.
When you need a professional roofing contractor to help determine the right gutter size, hire Tango & Gatti. Call us at (330) 303-4222, or you can contact us through our convenient online form. We serve Canton, Barnesville and surrounding OH areas.