Why "right the first time" matters
Most gutter problems we fix weren't caused by bad gutters. They were caused by bad layout: 5-inch gutters under a valley that needed 6-inch, one downspout trying to drain 50 feet of steep roof, or a downspout that empties onto a patio that slopes back toward the house. Those mistakes are cheap to avoid at install time and annoying to fix later.
This post walks through how we plan a layout. If you just want the 5-inch vs 6-inch answer, see 5-inch vs. 6-inch gutters.
Step 1: Read the roof
Before measuring anything, we look at how water moves on your roof:
- Roof planes. Each sloped section sheds water to one edge. Bigger and deeper planes send more water.
- Pitch. Steeper roofs move water faster; fast water can overshoot a small gutter.
- Valleys. Where two planes meet, the valley collects water from both and drops it in one spot.
- Upper roofs draining onto lower roofs. On two-story homes, a second-story downspout often empties onto a lower roof, adding that water to the lower gutter.
Step 2: Size each run
We size by run, not by house.
| Situation | Usually |
|---|---|
| Single-story, moderate pitch | 5" gutter, 2x3 downspouts |
| Long single-story rear run | 5" gutter, extra or 3x4 downspout |
| Two-story, large or steep plane | 6" gutter, 3x4 downspouts |
| Run below a valley | 6", or 5" with a downspout right at the valley |
| Lower roof taking an upper downspout | Size for both roofs' water |
| Porch, garage, small addition | 5" |
A 6-inch K-style gutter carries roughly 40% more water than a 5-inch. Our trucks roll both sizes on site, so mixing is easy.
Step 3: Place the downspouts
This is where installs most often go wrong.
Put a downspout near every valley
Valleys concentrate water. A downspout close to where the valley lands lets that water leave the gutter immediately instead of traveling down the run and spilling over.
Avoid overlong runs to one outlet
The farther water has to travel to a single downspout, the more the gutter fills in heavy rain. On long runs, we either add a downspout at each end or put one in the middle and pitch the gutter toward it from both sides.
Size downspouts for the load
A 3x4 downspout has about twice the opening of a 2x3. It drains faster and resists clogging from Kansas City's spring seed pods and fall leaves. We use 3x4 on 6-inch gutters and on busy 5-inch runs.
Think about upper-roof downspouts
When a second-story downspout empties onto a lower roof, the water hits the shingles hard in one spot and then floods the lower gutter. Options include running the downspout down to the lower gutter, extending it across the lower roof to the edge, or sizing the lower gutter for the extra water.
Step 4: Plan where each downspout drains
A downspout is only as good as where it empties. Before hanging anything, we look at:
- Grade. Does the ground slope away from the house at that corner?
- Hard surfaces. Will water run onto a patio, walk or drive that slopes back toward the house, or freeze in winter where people walk?
- Neighbors. Will water cross onto a neighbor's lot?
- Underground drains. Is there an existing buried line, and does it still flow?
- Distance. Can an extension carry water far enough from the foundation?
Much of the Kansas City area has clay-heavy soil that swells when wet and shrinks when dry, so dumping roof water at the foundation is a bad idea. Guidance for homes on shrink-swell soils calls for downspouts to discharge at least 3 feet from the foundation, beyond planting beds, and many contractors recommend more. Details in where should downspouts drain?
Step 5: Set the pitch
Gutters need a slight, steady slope toward each downspout. A common guideline is about 1/4 inch of drop per 10 feet. Too little and water sits; too much and the gutter looks crooked from the street and may leave the front edge low. We snap a line and check with a level on every run.
Step 6: Hang it to last
The best layout fails if the gutter falls off. We use hidden hangers screwed into solid fascia, spaced closely enough for Kansas City's snow and ice loads, and we tuck the back of the gutter under the drip edge so water can't get behind it. If the fascia is soft, it gets fixed first; see fascia repair.
Common layout mistakes
- One downspout for an entire long side of the house
- No downspout near a valley
- 2x3 downspouts on a 6-inch gutter
- Upper downspouts dumping onto lower shingles without a plan
- Downspouts emptying onto patios that slope toward the house
- Gutters hung dead level
- Extensions left off "for mowing" and never put back
What this means for your quote
When comparing gutter quotes, look past the price per foot. Ask how many downspouts each contractor is proposing, what size, where they go, and what size gutter is on each run. A cheaper quote with half the downspouts isn't a better deal if it overflows. Our quotes list it all, and our pricing is $13–$18 per foot installed including downspouts.
Plan it with us
An owner does every estimate. We walk the house, look at every roof plane and valley, and mark where each downspout goes and where it drains, then put it in a written quote backed by our 5-year workmanship warranty. Learn more about seamless gutter installation, downspout installation and our gutter size guide.
We plan and install across the metro, including new subdivisions in Olathe, Gardner and Raymore. Book a free estimate.
Common questions
How many downspouts does a gutter need?
At least one per run, plus extra on long runs and near valleys. Very long runs usually get a downspout at each end or one in the middle with the gutter pitched both ways. We plan it from the roof area each run collects.
What's the difference between 2x3 and 3x4 downspouts?
A 3x4 downspout has about twice the opening of a 2x3, so it drains faster and clogs less. We use 3x4 on 6-inch gutters and on busy 5-inch runs.
How much slope should a gutter have?
Enough to drain steadily toward the downspout without looking crooked from the street. A common guideline is about 1/4 inch of drop per 10 feet. We check pitch with a level on every run.
Can downspouts go in front of the house?
Yes, though we try to put them on corners or less visible spots where the drainage still works. Function comes first; if a front downspout is what keeps water out of the basement, it stays.