My neighbor was having some gutters replaced after a bad storm a few summers ago. When the contractor came to give my neighbor a quote, he offered to install either 6” or 5” gutters. We were wondering what is the standard residential gutter size?
Standard residential gutter size is 5” wide for K-style gutters. This measurement is taken from the top opening of the gutter. A 5” wide gutter is 3.5” deep. Gutters that are rounded are typically 6” wide and are 3.75” deep.
While there is a standard size of the gutter, there is a trend towards larger gutters. Larger gutters are more expensive but can also handle more water and are less likely to get clogged.
In this article, we’ll go over everything you need to know about gutter sizing, including sizing of different gutter styles, downspouts, and the pros and cons of various gutter sizes and types.
What is Standard Residential Gutter Size?
The most common gutter size found on a home is 5”. This measures the width of the open part of the gutter. The other measurement would be the depth of the gutter. This varies depending on the style of gutter you have, but most common are 5” K-style gutters which have a depth of 3.5”.
Rounded gutters are wider because they are not as deep, which means a 6” rounded gutter is the most common for rounded types. These gutters are 3.75” deep. They have significantly less capacity than K-style gutters, which makes them less common.
Sizes of Other Types of Gutters
A fascia gutter is more commonly found on commercial buildings and modern-style homes. It serves as both fascia and guttering, eliminating the need for installing a gutter over the fascia. Sizing for fascia gutters varies, although a 5”, 3.5” depth is common.
Box gutters are similar to K-style guttering in that they are deeper than curved guttering. Some prefer the look of box gutters over K-style. They also have a greater volume. Box gutters are not as common; therefore, typical sizes vary.
It is important to note that seamless gutters are not different from any of the above mentioned types of gutters. Seamless gutters use a roll of flashing run through a gutter machine that forms that flattened aluminum into a gutter shape – most often K-style or rounded, 5” or 6”.
Most new homes or gutter retrofits will have seamless gutters. They are seamless because installers can make them to nearly any length without having to connect seams.
What Size is Best?
The best gutter size for your house depends on the pitch of your roof, the square footage, and what geographical area you live in.
First, you need to know the watershed area of your roof. To do this, you’ll also need to know the pitch of your roof. You’ll multiply the square footage of your roof by the pitch “factor”. A 4:12 roof, for example, has a pitch factor of 1.05. Multiply your square footage by that number.
Next, find the rainfall intensity of your area. This takes into account the greatest possible 5 minute period of rain an area could potentially have. In the Southeast, this number will be around 7 inches an hour. Obviously, 7” an hour is impossible, but a gutter must be able to handle at least a minute or two of this intensity to function properly.
K-style and rounded gutters of typical width – 5” and 6” – are rated for an area they can drain effectively for 1” of rain per hour. A 5” K-style gutter can remove 1” of rain per hour from a roof of 5525 square feet or less.
The final step is to divide the square footage your desired gutter is rather for removing 1” of rain per hour by the rainfall intensity of your area. So for the 5” K-style gutter in the Southeast, divide 5525/7. The result is about 780 square feet. If your roof is larger than this, you’ll need a gutter larger than the 5” K-style type.
Are There Larger Styles of Gutters?
Gutters can be 7” or even 8” in width, depending on the style. Commercial box gutters are often made to drain huge roof surface areas, so the volumes must be much larger than a standard residential gutter.
Installers cannot create any type of gutter profile or size with their equipment. Most residential gutter contractors will have just one type of gutter machine, and certainly not more than 2. These machines typically make one size of the gutter, with one profile type. Thus, your local seamless gutter guy may not be able to accommodate your request for larger gutters.
K-style, fascia, and half-round gutter machines can pump out 7 or 8” gutters. You’ll have to make several phone calls to find contractors who are capable of creating gutters of this type. Commercial installers will be most likely to have the machines capable of creating much larger gutters.
How to Measure Gutters?
Measuring a gutter requires the measurement of two lengths – the width of the opening at the gutter and the depth of the gutter. The width of the top opening is the main measurement of a gutter and is how one would identify the gutter type. The depth, from the top opening to the bottom of the gutter, helps know the volume of water the gutter can handle.
Knowing the volume – or capacity – of a gutter seems like another useful stat to know. However, while you can determine the water capacity of the gutter, it is only helpful to use that number in the context of precipitation and run-off, which we’ll look at in the next section.
What Size Gutters Do I Need?
First, you need to know how much gutter you need for your house. For most homes, this is as simple as measuring the perimeter edge of your roof. For more complex roofs, you’ll have to measure each edge, unless you choose to leave some without guttering.
Once you’ve determined the amount of guttering needed, you need to know which size. Using our calculation above, we know we need to first find the rainfall intensity of the area we live in. For this example, let’s use Tampa, FL, which has a rainfall intensity of 7.8” per hour.
Next is determining the square footage of one face of the roof. One face is 40’ long by 20’ wide, which is 800 square feet. My roof is pitched at 6:12, so I multiply 800 by a pitch factor of 1.1, which is 880.
Knowing your desired style of guttering is key. Let’s say you want 6” half-round gutters. This type of gutter can handle 3840 square feet when the rain falls at 1” per hour. Divide 3840 by 7.8 and you get just under 500 square feet.
Therefore, I cannot use 6” half-round gutters on my house because they will not adequately drain my 800 square foot roof, as they will only handle a 500 square foot roof. Switching to 6” K-style gutters or a larger half-round is the better option.
Gutter Sizing Calculator
A calculator that determines that type of guttering and size is extremely useful, particularly when you are planning what type of gutter system you want for your home. Knowing the size of the gutter, you’ll need can help you envision what the exterior of your roofline will look like and inform your decision.
A gutter calculator requires you to know the length and width of your roof, the pitch, and the number of downspouts you intend to have. A key calculation is knowing how much longer one section of gutter will be per downspout.
Finally, the calculator requires you to input your city. If your city is not present, then choose one nearby or one you can safely assume receives a similar amount of rainfall as your own.
Cost of Various Gutter Sizes
The cost of gutters varies by place and time. Why time? Gutters are aluminum, and aluminum prices can fluctuate due to a variety of market factors. Measured by the linear foot, guttering costs are calculated in a dollar/linear foot format.
A standard, K-style 5” gutter costs anywhere from $6 to $15 per linear foot. Half-round guttering costs from $15 to $20 a linear foot. If you want something fancier, such as copper, then expect to pay upwards of $35 to $40 per foot. Galvanized guttering is slightly less – around $25 – $30 per foot.
Proper guttering is one of the best ways to waterproof your home. Failing to get proper guttering for your home can result in flooded basements, wet ceilings, and rotting roof sheathing. Left unchecked, a failed gutter can even cause mold and foundation issues.
Luckily, gutters are a fairly simple solution that, if you are willing, can be accomplished yourself. If you don’t have the time, hiring a contractor is one of the more affordable renovation projects that will also protect your home from moisture.
Remember, if you choose to gutter your house yourself, then be sure to use a calculator and properly size your gutters. Capturing all the run-off from your roof is essential to getting water as far away from your house as possible.