gutter size

Choosing the Right Gutter Size

What many people don’t know as they invest in a gutter system is they should be thinking about how large of a gutter they need. Although five-inch K-style gutters and six-inch half-round gutters are common with many homes, some properties need additional gutter support to prevent pooling and overflowing water.

Homes with large and/or steep rooflines require extra consideration as you install a gutter system.

Now, you may be wondering how do I determine the right gutter size on a steeper roof?

First, you’ll need to measure the roof’s pitch with a 2-foot level and a tape measure (the steeper the roof is, the more rain the roof collects when it’s windy). Take the level and level it against the roof. Measure the distance between the middle of the level and the roof.

A 5-inch gap between the midway point of the 2-ft level is a 5 in 12 (inch) pitch. Based on the measured pitch you can find the roof pitch factor which you will need later to calculate the right gutter size.

Roof Pitch                  Roof-Pitch Factor

12 in 12 or higher                 1.3

9 in 12 to 11 in 12                 1.2

6 in 12 to 8 in 12                   1.1

4 in 12 to 5 in 12                   1.05

Flat to 3 in 12                       1

Then get the square footage of the drainage area. On a gable-end roof, measure the slope of each. For more complex roof designs you’ll need to capture the area (length x width) of each.

Next, you’ll need to find the maximum amount of rainfall recorded in the city you live in via the US Weather Bureau. Keep in mind though it’s the worst case scenario ever recorded, it gives you a number to work off to protect your home in case of extreme weather.

Once you have the max rainfall over a five-minute interval, multiply that by the square footage of the drainage area and the roof-pitch factor.

Max Rainfall x square footage of drainage area  x roof pitch factor

The end number of adjusted square feet will help you decide on the right gutter size.

K-Style Gutter

5-inch      5,520 square feet

6-inch      7,960 square feet

Half-round Gutter

5-inch          2,500 square feet

6-inch          3,840 square feet

You may also want to consider how much easier it is to clean a larger gutter. Debris is less likely to clog up gutters and continue with proper water flow as you choose six inch or larger gutters.

For Amarillo homeowners needing assistance deciding on their gutter size and installing a gutter system, contact us today.

Comments for this post are closed.