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Size is a critical factor for gutters. Generally, 5-inch K-style gutters or 6-inch half-rounds are able to handle the rainfall on residential homes in many locations. However, houses with large and steep roofs in areas prone to heavy downpours may need wider gutters to prevent rainwater from overflowing. In this blog, a siding replacement contractor discusses how to determine the right size of gutters for your home.

Adjusting for Pitch and Rainfall

The first thing you need to do is calculate the square footage of the gutter’s drainage area. Once you accomplish this, you need to adjust for the roof-pitch factor and maximum rainfall intensity.

The main idea is that the steeper the roof’s pitch, the more rain it can collect. Measure the pitch with a two-feet level and a tape measure. Make sure you hold one end of the level right against the roof and then determine the distance between the roof and the underside of the level at its midpoint. This gives you a 12-inch run. For example, a 6-inch gap is a 6-in-12 pitch. Use the table below to find your 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

Meanwhile, the maximum rainfall for various regions is recorded by the U.S. Weather Bureau. A siding installation expert says that the higher the amount in your location, the larger your gutters need to be.

Sizing the Gutters

Multiply the calculated area by the roof-pitch factor and rainfall intensity in order to determine the adjusted square footage. Then use the information below as a reference to determine what size of gutters you need to install.

  • K-Style

    • 5-inch for 5,520 square feet

    • 6-inch for 7,960 square feet

  • Half-Round

    • 5-inch for 2,500 square feet

    • 6-inch for 3,840 square feet

Century Roofing and Siding is a leading provider of roofing and home improvement solutions in Ontario. We work with residential and commercial clients in and around Ottawa, ON, to provide roof repair, vinyl siding and gutter installation services. Call us at (613) 738-1774 or fill out this contact form to set up an appointment.