5-inch vs 6-inch gutters: which does your home need?
The short answer first, then the reasons, so you can tell whether a quote got it right.
Most homes in Western Washington do well with 5-inch gutters. Step up to 6-inch when a large section of roof drains into one gutter, when the roof is steep, or when two roof slopes meet and funnel water to one spot. Barns, shops and commercial buildings usually need 6-inch too. A 6-inch gutter holds nearly 2 gallons of water per foot, compared with about 1.2 for a 5-inch. That’s about 65% more. It pairs with a 3×4 downspout, which drains about twice as much roof as a standard 2×3.
Downspouts are named by their size in inches. A 2×3 is the standard size on most homes. A 3×4 is the larger size used with bigger gutters.
What determines the gutter size you need?
| Factor | Pushes toward 6-inch when… |
|---|---|
| Roof area draining to one gutter | The section of roof above one gutter is large, with nothing breaking it up. |
| Roof steepness | The roof is steep. Water comes off a steep roof faster, so more hits the gutter at once. |
| Valleys | Two roof slopes meet and funnel water to one spot above the gutter. That sends a lot of water to one place. |
| Heavy storms | Your home sees heavy downpours. Our rain is usually steady, but big winter storms bring real peaks. |
| Downspout count | There are few downspouts, or long stretches of gutter between them. |
| Building type | Barns, shops, machine sheds and commercial roofs. These almost always need 6-inch. |
What is the most common sizing mistake?
Gutters that are too small are far more common than gutters that are too big. It usually happens when a quote is based on the length of the roof edge instead of how much roof drains into it. Two houses can have the same length of gutter and very different amounts of roof above it. That’s why a newer home with clean, straight gutters can still overflow at one corner in hard rain. Nothing is broken. The gutter is just too small.
Do downspouts matter as much as gutter size?
A 6-inch gutter draining into a small 2×3 downspout is a bottleneck. The gutter holds more water, but the water can’t leave any faster. If you go to 6-inch, pair it with 3×4 downspouts. On an existing 5-inch gutter, adding a downspout is often a cheaper fix that works just as well. The rule of thumb is one downspout every 30 to 40 feet of gutter, or closer together if the roof is large or steep. More on downspout sizing.
Does 6-inch look different?
Slightly. It’s an inch wider at the top and a little taller at the front. On most homes nobody notices, and on larger houses it actually looks better. On a small cottage, a 6-inch gutter can look bulky. That’s one of the few real reasons to skip it when you don’t need the extra capacity.
Is 6-inch much more expensive?
A little. It uses more aluminum per foot, bigger downspouts and slightly more labor. On a full gutter job, the extra cost is small. It’s far cheaper than replacing a 5-inch system in three years because it couldn’t keep up. See what drives gutter cost in our cost guide.
Sources for the capacity figures: APCO puts a 5-inch K-style gutter at about 1.2 gallons per foot and a 6-inch at nearly 2, and Ask the Builder rates a single 2×3 downspout for about 600 square feet of roof and a 3×4 for about 1,200. We size every gutter when we measure for seamless gutter installation, and we add downspouts where the roof needs them — see downspouts and drainage. Most of that work is across Snohomish County.
Common questions
How do I know if my current gutters are too small?
Look for overflow in heavy rain when the gutters are clearly clean, especially in the same spot every time. Clogs cause overflow that moves around. Gutters that are too small overflow in the same place.
Can I use 6-inch on part of the house only?
Yes, and sometimes that’s the right call. For example, 6-inch on a big back roof and 5-inch on a smaller front. Just plan it on purpose, and don’t join the two sizes in the middle of a gutter.
What about 7-inch?
It exists, but it’s mostly for commercial buildings. If a quote for your home suggests 7-inch, ask what problem it solves. Usually, more downspouts are the better answer.
Does gutter shape change capacity?
A little. A fascia-style gutter is deeper and holds more than a standard K-style gutter of the same width. Size still matters more than shape.
Get a free written estimate
Call us or send your address. We will get back to you within 24 hours on business days to book a time to look at your gutters.