Residential gutters share some common denominators, but no two houses are exactly alike when factoring in architectural features, climate and microclimate. Purchasing a gutter system for your home involves a lot of decisions. One of the most important choices is the size of the gutter and the corresponding width or diameter of the downspout.
Gutter Size Basics
Gutters are designed to properly channel water into the downspouts. The size of the gutter should never be selected for the amount of water it can “hold.”
Gutter size refers to the opening at the top of the gutters and not to the depth of the gutter channel. Most residential gutter systems use 5” gutters or 6” gutters. A larger size gutter system will generally be more expensive.
Regardless of the gutter profile (the shape of the gutter), a gutter is measured from the back to the front, at the widest part.
K-style 5” gutters can easily channel a large volume of water.
While it might not seem like much, one inch more significantly impacts the amount of water a gutter system can handle. Six inch gutters typically channel anywhere from 30% to 45% more water than 5” gutters.
Determining Gutter Size
To determine what size of gutter is best for your home, combine the total square footage of the drainage area, roof pitch, gutter slope and the rainfall intensity (number of inches falling per hour). Other factors such a roof configuration, the gutter profile and microclimate (lots of trees growing near the house).
Gutter and Downspout Combinations
A standard 5 inch gutter system is typically accompanied by a 2 x 3 inch downspout.
K-style 6 inch gutters work well with 3 x 4 inch downpipes.
Depending on the size of the house and the amount of local rainfall, a 5 inch gutter paired with a 3 x 4 downspout might a more practical combination.