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How Many Downspouts Does Your House Need | Helpful Insight

How Many Downspouts Does Your House Need | Helpful Insight

It’s a question that always comes up, and you may have been too embarrassed to ask. But now is your chance! We’re going to give you some of our insights on how many downspouts your home needs.

It all depends on the size of the roof and the slope of it, but we’ll show you how to figure this out for yourself with a little math!

Before we go any further, let us describe a downspout and why we require one in our homes.

What are Downspouts and why is it important?

A downspout is a pipe which takes water from your roof and diverts it away to an area where the ground has been designed to handle the excess rainwater.

The main purpose of this system is to protect our homes’ foundation by moving any potentially harmful (or helpful) liquids that could be seeping into our home’s structure, protecting our homes from water damage.

A downspout is important because it prevents water damage, which can be harmful to our homes’ foundation. Water damage can cause mold and mildew growth as well as attract insect infestations like termites or carpenter ants.

Why Are Downspouts Important?

Downspouts are determined by these two factors

There are a few things to think about when it comes to the number of downspouts needed for your home. This all depends on the size of your roof and the slope of it.


A roof size can be roughly determined by measuring your home’s square footage (length x width). This will give you a decent estimate of how many downspouts are necessary to provide proper drainage.

The general rule is that one downspout should drain for every 150 sf or .33 of a downspout per every 150 sf.


The slope of your roof is also important when considering how many downspouts are necessary for proper drainage. A good rule of thumb to follow is that one downspout should drain 20% or .20 in order to handle the excess water from 100 square feet.

If you’re having trouble figuring out your roof’s slope, we recommend using a measuring tape. Simply measure the height of one side or corner and then use this to compare to the other sides/corners.

The point in which all heights meet is where your roof begins its peak and it will most likely be in line with any towers on top of your home.

Is it better to have one downspout or two? What is the proper number of downspouts for your home?

Having one downspout will provide the most minimalistic approach to water drainage and is recommended for homes that have a roof size of under 2000 sf.

For larger roofs, or more heavy duty storm seasons, having two downspouts on each side of your home would be ideal in order to ensure proper water runoff. This option may be a little more expensive, but will provide the most efficient drainage.

In regards to how many downspouts you need for your home, just remember that one or two downspouts is ideal and can be determined by measuring your roof’s square footage.

What is the ideal size of downspout for your property?

The ideal size for a downspout depends on the roof’s square footage and slope.

A common rule of thumb is that each downspout should drain 20% of the overall length, which can be achieved by measuring your home’s length and width to determine its square footage.

For example: If you have a house with 150 sf,  you want one downspout to drain for every 150 sf. This would mean that you’d need approximately .33 of a downspout per each 150 square feet (or one every five feet).

If your home has 100 feet by 50 feet, then you’ll require two downspouts on either side in order to properly drain the roof.

In regards to the size of downspout that is best for your home, you want a pipe or tubing that will be able to handle any excess water from heavy rainfalls.

If you have a large roof and it frequently rains heavily in your area, then we recommend going with a larger diameter downspout (in order to allow more water to flow through).

If you have a smaller roof and it doesn’t rain that much in your area, then we recommend going with a smaller diameter downspout (in order to decrease water buildup in the pipe.

Just remember: The larger the downspout size is, the more heavy duty and efficient drainage will be provided. It’s up to you and your area’s specific needs.

In conclusion, a downspout should be determined by the size of your property and roof slope in order to provide proper drainage from heavy rainfalls.

For homes that have smaller roofs or less heavy duty storm seasons then one or two downspouts will suffice however for larger roofs with more excessive rainfall, two downspouts per side will provide the most efficient drainage.

How Many Downspouts Do Your House Need?