Quick answer
5 inch or 6 inch gutters in the Tri-Valley: If a clean gutter sheets water over the front edge in a December storm, that is a capacity problem, not a debris problem. A 6 inch gutter carries roughly 40 percent more water than a 5 inch, with larger downspouts to match, and it belongs on runs over 40 feet that cannot take a second downspout, any run over 60 feet, lower gutters catching an upper roof, and inside valleys that overflow. If your run is under 40 feet, has a downspout, takes no upper roof and does not overflow in a real storm, 5 inch is fine. Call (925) 905-9555 or get a free quote online.
The number that matters
Annual rainfall is the wrong number. Peak flow is the right one.
Picture it: December, a real storm, water pouring over the front of a gutter you had cleaned six weeks ago. There is nothing in it. That is one of the most common calls we get in the valley.
San Ramon gets somewhere around 18 to 20 inches of rain a year depending on where you live in the valley. Compared with most of the country east of the Rockies, that is not much, and it is why gutters here get treated as an afterthought.
But a gutter does not have to survive the yearly total. It has to survive the most water that hits it in a single hour. Research from the Center for Western Weather and Water Extremes at Scripps found that in Northern California, roughly 60 to 120 hours of rain each year deliver more than half of the annual total. Most of our water arrives in a handful of atmospheric river events, and one of those can drop an inch in an hour.
So your gutter does not experience 20 inches spread over twelve months. It experiences an inch an hour, several times a winter, with drizzle in between. Size a system for the average and it fails during exactly the events that cause damage.
The builder default
Why so many valley homes have a 5 inch system
Five inch is the builder default across the country. That is not a criticism. It is a description of how tracts get built.
On a development of several hundred homes, the gutter is specified once, priced by the foot and installed the same way on every roofline, regardless of what that particular roof does with water. 5 inch gutters handle a great many homes here perfectly well. But specified once for the subdivision is not the same as sized for your roof, and the gap shows up in a hard December rain.
What actually decides whether a gutter overflows is how much roof area drains into a given run, how long the run is, how many downspouts it has, and whether water is being fed into it from above. A 40 foot run with a single downspout collecting a big roof plane will struggle however clean it is. The water has nowhere to go.
A note for Dougherty Valley
If you live in Windemere, your neighborhood was built between roughly 2002 and 2006, which puts those gutters at about twenty years old. Gale Ranch went up in phases from 2003 through the late 2010s, so it varies more by street. Two things follow. First, age: twenty-plus years of thermal cycling loosens hangers, opens seams and flattens the pitch that moves water to the downspout. A section that has sagged half an inch overflows at that low point long before the rest of the run is anywhere near capacity, so what looks like a sizing problem is sometimes a gutter repair. We check that first, because it is the cheaper answer and often the right one.
Second, the original spec. These are large homes with complex rooflines, several gables, and upper roofs draining onto lower ones, all fitted with the same builder-grade 5 inch profile. Some of those rooflines were always going to outrun the gutter attached to them. We see it across Dougherty Valley and out toward Camino Tassajara.
How we size it
What each gutter size is actually for
A 6 inch gutter is only an inch wider than a 5 inch, which is why the difference gets dismissed. It carries roughly 40 percent more water, and the downspouts that pair with it are larger too. That is the difference between coping with an atmospheric river and giving up at the front lip.
| Size | Best suited to |
|---|---|
| 5 inch | Runs under 40 feet with at least one downspout, that do not overflow in normal rain and are not receiving water from an upper roof. |
| 6 inch | Runs over 40 feet that cannot take a second downspout. Any run over 60 feet. Lower gutters catching water from upper gutters. Rooflines that funnel a large area into a short section. Inside valleys that overflow in heavy rain. Metal roofs. |
| 7 inch and larger | Unusual rooflines and high-volume situations. Less common on homes, but available when the math calls for it. |
| Mixed sizes | You do not have to pick one size for the whole house. 6 inch on the two problem elevations and 5 inch elsewhere is often the most cost-effective answer. |
That last row is worth sitting with, because most homeowners assume it is an all-or-nothing replacement. It usually is not. If one side of your house handles storms fine and the north elevation floods every year, that is where the money should go. For what a full or partial job costs, see what gutter work actually costs in the Tri-Valley.
When 5 inch is genuinely fine
- The run is under 40 feet.
- It has at least one downspout, and the downspout drains freely.
- No upper roof is draining onto it.
- It does not overflow during a real storm.
- Pitch is still even, with no standing water after rain.
- If all of that is true, leave it alone. Upsizing a system that is not struggling wastes your money.
Find out which you have
Diagnose it yourself in the next real storm
You do not need us to start. The next time a real storm comes through, take a walk around the house with an umbrella and pay attention to where and how the water leaves the gutter.
| What you see | What it usually means | Usual fix |
|---|---|---|
| Water spilling over the front lip along a long stretch of clean gutter | Capacity: too much roof for the run | Larger gutter on that elevation, or an added downspout |
| Overflow at one low point while the rest runs fine | A sag or a hanger that let go | Re-hang and re-pitch the section |
| Water shooting past the gutter where a valley dumps in | Concentration: two roof planes feeding one spot | Larger gutter or a diverter at that corner |
| A downspout putting out a trickle while the gutter fills | A clog in the downspout itself | Clear and flush the downspout |
| Damp soil at the same spot on the foundation every winter | Discharge too close to the house | Longer extension or underground drainage |
Note which elevation and roughly where. Five minutes of that is more useful than anything we can work out from the ground on a dry day. If you have not had the gutters cleaned yet this season, start with our rain-ready checklist so you know a clog is not muddying the picture.
What our free roofline assessment covers
- Walk the house.A Solutionist walks every elevation and asks where you have seen water go.
- Measure the runs.Each run gets measured, and downspouts get counted against the length.
- Map the roof planes.We look at where planes drain, where valleys concentrate water and where upper roofs feed lower ones.
- Check what is there.Pitch, hangers, seams and fascia on the existing system, since a repair may solve it.
- Recommend a size per elevation.Sometimes a full installation in 6 inch. Sometimes one side. Sometimes re-pitching what you have.
- Put it in writing.A free written estimate, and a straight answer either way.
Clean gutters still overflowing? Let us size it to your roof. Call (925) 905-9555
Book a Roofline AssessmentFrom the crew: going to 6 inch gutters and keeping the old small downspouts is a common half fix. The system drains at the speed of its narrowest point, so the gutter and the downspout have to be sized together.
Frequently Asked Questions
Only if your roof calls for it. Runs over 40 feet that cannot take a second downspout, any run over 60 feet, lower gutters catching an upper roof, inside valleys that overflow and metal roofs are good candidates. Shorter runs with a downspout that do not overflow in real storms are fine at 5 inch.
Roughly 40 percent more than a 5 inch gutter, and the downspouts that pair with it are larger as well. That is why one inch of width makes a big difference in an atmospheric river storm.
Because the run is getting more water than it can move. That happens when too much roof area drains into one run, the run is long with one downspout, an upper roof feeds it, or a valley concentrates water at one corner. A sag at one point can also cause overflow there.
No. Mixed sizes are common and often the most cost-effective choice. Put 6 inch on the elevations that overflow and keep 5 inch where it is working.
Check for sagging, loose hangers and open seams first. Twenty years of thermal cycling flattens pitch, and a sag can look like a capacity problem. If the run is sound but still overflows, upsizing that elevation is the next step.
Yes. A Solutionist measures your runs, maps where the roof drains and checks the existing system, then gives you a written recommendation. Call (925) 905-9555.
Free estimates
Clean gutters, still overflowing? Let us size them for Tri-Valley storms.
Free roofline assessments and written estimates from local Solutionists. Seamless gutters formed on site and sized elevation by elevation, from 5 inch to larger profiles when your roof calls for it.
The Brothers That Just Do Gutters · San Ramon · (925) 905-9555 · Serving San Ramon, CA and the Tri-Valley
Licensed, Bonded & Insured · California Contractor License #1115646