The difference is two dollars a foot and the capacity to handle a March melt. Here is how we decide, run by run.
A five-inch K-style gutter carries roughly 1.2 gallons per linear foot and drains about 5,500 square feet of roof per downspout in a one-inch-per-hour storm. A six-inch gutter carries about 2 gallons per foot, drains roughly 7,900 square feet per downspout and takes a three-by-four downspout that is less likely to freeze solid or clog with cottonwood seed. On most Wasatch Front homes the price difference is about $2 per foot, or $300 to $500 on a whole house.
Most Utah ranches and two-stories on the valley floor are fine with five-inch. Bench and mountain homes, steep roofs, long eaves and metal roofs usually need six-inch on the main runs. We quote size run by run rather than one size for the house, which is why many of our installs are six-inch on the back eave and five-inch on the porch.
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Downspout count matters as much as gutter size. One downspout per thirty to forty feet of gutter is the rule; many builder installs have half that, which is why corners overflow. Adding a downspout to a five-inch run is often cheaper than upsizing and solves the same problem. We look at both on every estimate. See downspouts and extensions.
Five-inch seamless aluminum is $8 to $12 per foot installed and six-inch is $10 to $14, with two-by-three downspouts at $100 to $150 and three-by-four at $125 to $175. Full ranges are on the installation cost guide.
Compare the rest of the family: K-style, half-round, box and fascia gutters, five-inch vs six-inch, aluminum, steel and copper, and gutter colors. Or start at the gutter types overview.
On most homes the extra inch is barely noticeable from the street. On a small cottage with low eaves we usually stay with five-inch and add downspouts instead.
Yes, and we often do: six-inch on the main eaves that carry the most roof, five-inch on porches and small sections.
Yes, six-inch hidden hangers, and we space them closer on heavy-snow eaves.
No. Ice dams come from roof heat loss and shade. Six-inch reduces overflow and freezing in the gutter, and heat tape addresses the ice.
