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Integrity Exteriors

Gutter Size Guide for Kansas City, MO

Most Kansas City, MO homes are fine with 5-inch K-style gutters, which hold about 1.2 gallons per foot and drain up to roughly 5,520 square feet of effective roof area. Homes with large roof planes, steep pitches, deep valleys or a history of overflowing need 6-inch gutters, which hold about 2.0 gallons per foot and drain up to roughly 7,960 square feet, paired with 3x4 downspouts.

Section 01

The Numbers That Decide Your Gutter Size

  • 5-inch K-style: holds roughly 1.2 gallons per linear foot, serves up to roughly 5,520 square feet of effective roof area.
  • 6-inch K-style: holds roughly 2.0 gallons per linear foot, serves up to roughly 7,960 square feet of effective roof area. That is roughly 50 percent more capacity than 5-inch.
  • 2x3 downspout: drains roughly 600 square feet of roof area, moving in the range of 30 to 40 gallons per minute.
  • 3x4 downspout: drains roughly 1,200 square feet of roof area, moving in the range of 110 to 145 gallons per minute.
  • 3-inch round downspout: roughly 706 square feet.
  • 4-inch round downspout: roughly 1,255 square feet.

Section 02

Why Kansas City Rainfall Intensity Matters More Than Annual Rainfall

Kansas City averages roughly 39 inches of precipitation a year, with June at about 5.5 inches, May at about 5.1 inches and August at about 4.4 inches, spread across roughly 107 precipitation days.

Annual totals are not what overwhelms a gutter. Intensity is. In this region, short-duration rainfall intensity for a 10-year design storm approaches seven inches per hour, and a 100-year event approaches nine and a half inches per hour. A gutter does not care that it only rains 39 inches a year. It cares what happens during the fifteen minutes when a June thunderstorm parks over your roof.

That is the case for sizing generously in Kansas City. A 5-inch gutter with a single 2x3 downspout on a 40-foot run will pass a gentle spring shower and sheet water over the front lip during the storm that actually threatens your foundation.

Section 03

How To Tell If Your Kansas City Home Needs 6-Inch Gutters

  • Your gutters overflow in heavy rain even when they are clean.
  • You have large, uninterrupted roof planes feeding a single run.
  • Your roof is steeply pitched, which increases the effective drainage area and accelerates runoff.
  • You have deep valleys dumping a large volume onto a short section of gutter.
  • Your roof has multiple planes converging above one gutter run.
  • You have had chronic basement seepage or foundation issues on one elevation.
  • You have a metal roof, which sheds water faster than asphalt shingle.
  • You are already replacing gutters and want to avoid ever revisiting this question.

Section 04

Downspout Count Is As Important As Gutter Size

The single most common sizing error we correct on Kansas City homes is too few downspouts. As a working rule, plan one downspout for roughly every 30 to 40 feet of gutter run, adjusted for the roof area feeding that run. A long run with one outlet creates a bottleneck no gutter size can fix. Moving from a 2x3 to a 3x4 outlet more than doubles the volume the outlet can pass and dramatically reduces clogging.

Frequently asked questions

Gutter Size FAQs

For most homes with average roof planes and adequate downspouts, yes. For large, steep or valley-heavy roofs, 6-inch is the safer specification given Kansas City's storm intensity.

Roughly 2.0 gallons per linear foot against roughly 1.2 gallons for 5-inch, about 50 percent more capacity, and it serves roughly 7,960 square feet of effective roof area against roughly 5,520.

They should have them. Putting a 2x3 outlet on a 6-inch gutter re-creates the bottleneck you were trying to eliminate.

Metal sheds water faster and carries snow loads differently, so 6-inch gutter with 3x4 downspouts and appropriate snow retention on the roof is generally the right specification.

In nearly all cases, yes. We check fascia height and roof edge detailing at the estimate.

Multiply the footprint area of each roof plane by a pitch factor to get effective drainage area, then compare that number to the capacities above. We do this calculation for you at the free estimate.

Related: seamless gutter installation, downspout installation, gutter replacement and the Kansas City gutter cost guide.

Not sure what size you need? Call 979-479-1000 and we will size it on site, free.

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