Is heavy rainfall in the forecast? We’ve got you covered
K-style and half-round gutters are the two common gutter styles used on homes today.
A standard gutter size is 5 inches, but 6-inch gutters work better for areas with heavy rainfall.
An extreme roof pitch can also require you to size up.
When it comes to gutters and downspout sizes, you can’t just eyeball the situation. Ensuring a proper fit that will prevent clogs, buildup, and moisture damage from affecting your roof requires careful measuring. Plus, downspout placement is just as important as downspout size for efficiently directing rainwater away from your roof. In this guide, we’ll help you figure out the best gutter size and downspout combination to protect your home, rain or shine.
To figure out the gutter size you need, you can calculate the square footage of your gutter's drainage area. A basic gable-end roof will require calculations for both slopes. If you have a hip roof, you'll need to calculate the area of each individual surface that contains a drainage area. The equation for total square footage on every surface area of your roof is always length x width.
"If you have a hip-and-ridge roof, you are more likely to be able to install smaller gutters. This is because the water is distributed across more slopes than if it was a classic gable roof with only two slopes," says Jose Figueroa, Gutter expert at Artisan Quality Roofing.
| Roof Square Footage | Gutter Type | Recommended Gutter Size |
|---|---|---|
| Up to 5,500 | K-style | 5 inches |
| 5,500–8,000 | K-style | 6 inches |
| Up to 2,500 | Half-round | 5 inches |
| 2,500–3,850 | Half-round | 6 inches |
Did you know that there are different gutter styles to choose from? Your gutter gauge or thickness should be sized based on the efficiency and capacity of the gutter style you choose.
K-style gutters are the most common gutters you'll see on residential homes. You'll know them by their signature front edge that matches the home's crown molding. This option is praised for being durable, versatile, and easy to install.
If you're choosing K-style gutters for a roof area under 5,500 square feet, the recommendation is a 5-inch standard gutter size. For roof areas between 5,500 and 8,000 square feet, the recommendation is a 6-inch gutter.
Half-round gutters are more commonly used on historic homes. They can also complement classic-style new constructions. While half-round gutters offer aesthetic benefits, they generally don't move water as efficiently as K-style gutters.
For roof areas under 2,500 square feet, 5-inch half-round gutters are recommended. Roof areas between 2,500 and 3,850 square feet require 6-inch gutters.
Once you've calculated the square footage for each drainage section, it's time to focus on special considerations.
If your home has a steeper roof pitch, there's a high risk for windblown rain to collect in your gutters. You'll want to size up your gutters because rain will be running off the gutters at a faster pace compared to other roofs. Steep roof pitches—even smaller roofs—benefit from 6-inch gutters.
The National Weather Service refers to the number of inches of rain that can fall per hour based on a 5-minute sample period as a region's maximum rainfall intensity. If you live in an area with a high maximum rainfall intensity, you'll need larger gutters to prevent your system from becoming overwhelmed in heavy, sudden rains.
Seven-inch and 8-inch gutters are rarely used in residential buildings, though there are cases where they work—for example, an extraordinarily large house with steep roofing. A home that gets heavy rainfall should be fine with a 6-inch gutter.
Generally, larger gutters require custom ordering with professional gutter installation due to the extra weight. You may also be able to use traditionally sized gutters by having a professional increase gutter pitch during installation to increase capacity. However, you should make sure you install gutters in the right place—as close to the shingles as possible—to prevent expensive problems.
The downspouts in a gutter system play an important role because they make sure water drains efficiently. The general rule about placing downspouts is that you need one downspout for every 25 to 35 linear feet of gutter. The maximum gutter length between downspouts is 40 feet. If you're in a high-capacity situation due to either roof pitch or rainfall levels, adding extra downspouts can boost your gutter's drainage capacity.
You should also install downspouts so that they are positioned to move rainwater away from your home's foundation. Downspouts that do not adequately drain away from your home's foundation will eventually cause water to seep into your basement and foundation. If you're unable to place downspouts in a way that directs water away from your home's foundation, you may need to utilize gutter extensions.
| Gutter Type | Gutter Size | Recommended Downspout Size |
|---|---|---|
| K-style | 5 inches | 2x3 inches |
| K-style | 6 inches | 3x4 inches |
| Half-round | 5 inches | 3–5-inch diameter |
| Half-round | 6 inches | 4–6-inch diameter |
If your roof's square footage requires 5-inch gutters, you'll need a 2-inch by 3-inch downspout. That creeps up to a 3-inch by 4-inch downspout for 6-inch gutters. It's necessary to create custom downspout solutions for gutters wider than 6-inches that are being installed to address excessive pitch or rainfall levels.
Round downspouts come in 3-, 4-, 5-, and 6-inch diameters. These downspouts are also available in a variety of colors to match your home. Contractors typically provide guidance on how to choose the right size based on the specifics of a home's roofing system. The 6-inch option generally works best for most homes.
Contact a licensed contractor specializing in gutter installation and make sure they’re experienced in installing the type of gutter you want. Gutter installation is challenging. You face considerable risks working high above the ground. Poorly installed gutters cause more problems, are expensive to repair, and can affect your insurance and home warranty claims.
Hiring a pro installer will save you money in the long run. On average, gutter installation costs $4 to $40 per linear foot.
The standard size for residential gutters is 5 inches. Some houses opt for 6-inch gutters to stand against heavy rain since they can hold significantly more water. Five-inch gutters are 3.5 inches deep, and 6-inch gutters are 3.75 inches deep. If you have an all-tile or all-metal roof, you’ll need at least 6-inch-wide gutters.
When connecting a gutter to a downspout, make sure that both have the same outlet capacity. Meaning starting from your gutter and moving downwards, the diameter should match so you have a secure seal. Make sure you’re working downwards when attaching the pipes (for example, the gutter fits inside the downspout) as doing the reverse will cause leaks.
Larger gutters can handle more rainfall and more debris without disruption. If you live in an area that gets a lot of rain (or you’re surrounded by many trees), sizing up may be a good idea. Keep in mind you should still regularly clean your large gutters to keep leaves and large debris from clogging.
