Downspouts on rain gutters help move water away from the foundation of a building. They also prevent clogging.

To install a downspout, start by measuring from the gutter’s top to where you want the downspout to end. Add an inch and a half to this figure to account for the top elbow and another downspout section.

Length

The gutters on a house or building are designed to divert rainwater away from the walls and foundation. Without this, water can leak down through the masonry and cause major damage over time. Downspouts are connected to the ends of the gutter and emptied into a drainpipe that runs through the ground or down to the street. They are usually designed with a ramp that keeps the water moving and prevents it from pooling around the foundation.

A downspout is normally made of aluminum, steel or zinc. Its length depends on the size of the roof, the climate in your area and how much rain you get. It is important to install the right amount of downspouts so that the rainwater will be diverted from the roof and not overflow the gutter.

To determine how long you need a downspout, start by measuring the length of the gutter section from where the downspout will attach to the side of the house. You can then figure out how much material you will need for the downspout by subtracting that measurement from 10 feet (3.0 m). Next, add the number of elbow pieces that will be needed for the downspout and calculate how many straight lengths of downspout are required. Lastly, calculate the length of the bottom downspout to make sure that it will be long enough to keep water away from the foundation.

Slope

Rain gutters need to be properly sloped in order to work effectively. Gutter systems that are not pitched adequately can cause damage to walkways, driveways and foundations. In addition, clogged gutters are ineffective and can lead to water damage to the home. It is a good idea to hire a professional if you don’t have the necessary experience to do this job yourself.

Run a string along the length of the gutter to determine where you will need downspouts. It is best to use a level on the ground to make sure the string is perfectly horizontal. It is important to slope the gutters enough to get the proper flow of water, but not so much that they look unsightly. Ideally, gutters should be sloped about a half inch for every 10 feet.

To install a downspout on the gutter, attach one of the gutter’s elbows to the end of the outlet tube protruding from the wall. Then, use a hacksaw to cut a short section of downspout material that connects the two elbows and reaches the side of the building. If you need to, add another downspout extender at the front or back of the gutter to ensure that it reaches a sufficient distance away from the foundation. Fasten the downspout sections together by driving primed sheet-metal screws into predrilled holes. It is a good idea to have a helper for this step, so one person can hold the gutter in place and the other can fasten the pieces together.

Attachment

Downspouts connect to the underside of a gutter and direct rainwater to the ground, where it can flow into rain barrels or underground drain pipes. They’re usually angled 75 degrees from the house, which helps prevent clogs and improve water flow. It’s best to put all the pieces together on the ground, so you don’t have to do it while up on a ladder. You’ll need an elbow for the gutter hole, a downspout section that fits into it and a downspout outlet tube. The outlets are available in different sizes, so you’ll need the right ones for your gutters.

To attach the downspout to the gutter, use a jigsaw to cut a square opening at the bottom of the gutter. Make the downspout section long enough to extend an inch or two above the top of the gutter, then crimp its edges with needle-nosed pliers to create a clean connection. Fasten the downspout to the gutter and the outlet tube with pop rivets or screws.

If you’re installing a downspout to empty into a rain barrel, place a concrete paver at the bottom of the outlet tube. You can also set it on a level section of sidewalk, which will help control the flow of rainwater as it drains. Some people also divert their gutters to their yard or other landscape features, such as a garden pond or an old swimming pool.

Cleanliness

Downspouts keep the gutter system clean by draining away leaves and other debris, which can clog or block a rain gutter. Clogged gutters are a major source of water leaks around the foundation and can weaken the structure of your home. Downspouts also help direct water away from the house, which can prevent rot and wood damage in your fascia, siding and other structures around the property. Gutter guards can further decrease the chances of downspout clogs.

Gutter downspouts can be made of various materials — aluminum, vinyl and steel are popular choices — but the material you choose should match your gutters. For example, you should not attach a metal downspout to an aluminum gutter because they won’t fit securely together.

You can install downspouts on an existing gutter system by driving primed sheet-metal screws through predrilled holes at each joint in the downspout section. Always use two screws at each joint so the upper and lower sections can tuck into each other without separating, which will cause a leak. You can also cover the joint at the top of the downspout with a strip miter, a 3-inch-wide strip of aluminum.

The location of the downspout is important, because you want it to be located where the ground slopes away from your shed. This will help ensure that water doesn’t pool near the shed, saturate the soil and leach into the foundation.