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What Size Gutters Do I Need?

what size gutters

When fixing up your home and doing most of the repairs and additions yourself, you’re going to come across some things you don’t know. One of these things you may not know until you’re getting ready to install is the size of gutters you need for your house.

The answer to this question varies somewhat based on the type of gutter system you are installing and of course the size of the roof you are guttering. These tips will help you figure out exactly what you need.


If you’ve chosen a K-style gutter, you’ll usually have the choice of five- or six-inch products, especially for a residential house. Anything larger than six inches would be meant for churches or commercial buildings. If your roof area is under 5,500 square feet, a five-inch K-style gutter is recommended. If your roof area is between 5,500 and 7,900 square feet, go with a six-inch gutter instead. In both cases, a three-inch by four-inch downspout would be appropriate.


Half-round systems don’t move as much water as K-style systems do, but they are more historically accurate gutters for old houses. After you calculate your roof’s square footage, you can select the size of the gutter you need. If your roof area is under 2,500 square feet, choose a five-inch half-round gutter, and if your roof area is between 2,500 and 3,840 square feet, choose a six-inch option.

In an area with heavy downpours, you may want to go up to seven or eight inches for either K-style or half-round gutter systems. You may have to have these professionally installed, though, because in most cases, these bigger sizes are not readily available to do-it-yourself homeowners.

It’s very important to keep in mind the smaller capacity of half round gutters because while I love the look of them they can very easily be overwhelmed causing big issues. When in doubt install the next size larger.

Downspout Placement

Installing a gutter system involves more than just the gutters themselves. You need to also install downspouts. Downspouts are the part of a gutter system that forms the connection between your roof and the ground, thereby allowing rain or snowmelt to move from the roof to the ground. Just one inch of rainfall on a roof that is 1,000 square feet equals more than 600 gallons of water moving through your gutter system!

Rather than deal with leaks and basement seepage after you install your gutter system, it’s more cost-effective to place downspouts properly in the first place so that the volume of water draining into the ground is reduced. The following steps should be taken to ensure that your downspouts are spaced adequately and installed correctly to prevent water leaks later.


In general, you should have one downspout for every 40 linear feet of gutter. This placement allows for proper drainage and will keep the gutter system from overflowing during heavy rain. When rainwater overflows the gutter system, it bypasses the downspouts altogether and lands on the ground right next to your foundation. This can lead to leaks and even cracks in your foundation, which are much more expensive to repair than installing the right number of downspouts.


Downspouts must be positioned so that they move water away from your foundation. You do not want the water to adequately drain from your roof only to pool at the spot where your downspout discharges, which will then seep into your basement or around your foundation. Also, be aware of any type of landscaping that could act as a dam and move water back toward the foundation. This has the same effect as having no downspouts at all.

Downspout Extensions

If you are unable to position your downspouts so that they move water away from your house and foundation, you may need to invest in downspout extensions to move the water to a safe distance away from your house. You will want to choose extensions long enough so that the water is discharged no fewer than four feet from your foundation.

Splash Guards

Splash guards are typically made of aluminum and are secured at the edges of your gutter system where your roof valleys are located to prevent water from splashing out as it flows along the edge of your roof to the downspouts. When water splashes out, it’s bypassing your designed system to move the water away from your foundation. These guards are available in the same color as your gutter system, so they will not stand out in any way.

You may need splash guards if you notice that mud has splashed up against your house after heavy rainfall. If mud is splashing up, so is water, meaning there’s a risk of improper drainage and water leaks. Fortunately, splash guards can be installed at any time after your gutter system is installed, so it’s not something that must be done as you’re installing your system. Splash guards can also be installed at the end of your downspouts as well.

Leaf Guards

Also keep in mind that if you have those big beautiful trees around your house you will definitely be needing leaf guards or you’re gonna be spending a lot of time cleaning your gutters from all the debris that accumulates.

Clogged gutters are worse than no gutters because they channel water right into the soffit where it can cause serious rot.

Installing a gutter system on your house is definitely a project you can accomplish on your own, especially if you know what size and style you need and where to place the downspouts. Armed with this information, you’re ready to protect your home from rainwater, flooding, and leaks.

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4 thoughts on “What Size Gutters Do I Need?

  1. This is an interesting blog. I have a 110 year old cottage I am restoring in Canada. Your blog has been the best information I’ve found.
    One issue with gutters and my cottage is that it did not have any when built. It had exposed rafter ends showing in craftsman style and looked amazing. Then someone added tacky wood facia, soffits and gutters. It killed the original charm. I’ve been wondering if I can remove at least some of it? Or perhaps instead of gutters dig French drains with channels leading away from the cottage. You did not address other options like that, or what to do if your property did not have gutters.
    My cottage sits on a raised cement footing. So your blog made me ask these questions. Perhaps you can answer here or in another blog sometime.
    Wendy Peter

    1. I like half round gutters on bungalows with open rafter tails. I would remove the fascia that was added and then add half rounds gutters which still show the rafter tails a bit unlike K-style gutters.

  2. Very Good information here. I have a friend I will forward your blog to as his home was built without gutters and he has had to pay for major foundation repairs. Even though they guarantee the work, during heavy downpours, he has three areas where the water is damaging and he had not yielded my advice to get quotes for gutters. Even if just for a few of the areas where two valleys unit and then over the main entrance and rear yard would benefit. Thanks for writing this…I didn’t know about a splash guard but with his high pitched roof, my guess is that he does need a few of those in the two valley area of the edge.

  3. Any recommendation about what kind of leaf/gutter guards are most effective? There are plastic types, some with screen/mesh, open mesh (aluminum) and even foam. I’m overwhelmed by the pros and cons. Sounds like some restrict water and freeze over, some allow leafs and debris to pass, some capture maple helicopters and pollen, some (foam) are even accused of growing vegetation, dry rotting and eventually creating more of a maintenance headache than benefit. Thank you for your contribution and support for old homes.

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