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When it comes to downspout extensions, are you coming up short?

If I was a betting man, I would put money on finding a moisture issue at every inspection I perform due to improper grading or drainage. Sure, I would lose money once in a while, but the odds would be in my favor. Many of the houses that I inspect are either lacking downspout extensions all together, the extensions are too short, or the grading next to the house allows water to run back to the foundation or up against the structure. One of the best ways to ensure that your home continues to look and perform well is to make sure that you have properly installed downspout extensions that discharge water a minimum of 4 to 6 feet away from your foundation or structure. And sometimes, they need to be even longer!

During a storm, ALL of the water that lands on the roof surface is directed to the roof drainage system which is composed of the gutters (a.k.a eavestroughs), the downspouts and the downspout extensions. To give you some perspective on the amount of water that is being discharged off of your roof, consider this: A roof with 1000 square feet of surface area will shed approximately 623 gallons of water for every inch of rain that falls during a storm. For those that are interested, here is the math: 1000 square feet = 144,000 square inches : 1 cubic inch holds 16.387064 mL of water : 144,000 cubic inches x 16.387064 mL = 2,359,737.216 mL : 1 gallon = 3785.41 mL : 2,359,737.216 mL / 3785.41 mL = 623.37691716353 gallons!!

I am guessing that you were a little shocked after reading about how much water was being collected and deposited next to your house by the roof drainage system. Don't feel too bad though, most homeowners do not realize how much water comes off a roof. Now that you know how much water is shed off of a roof, lets talk about how to get that water away from the house.

The primary focus of this article is downspout extensions, but in order for your roof drainage system to work properly all of the components must be properly installed, maintained in good condition, and cleaned on a regular basis. Think of the extra information as a bonus! I like to start at the top and work my way down...much like water from the roof.

1. All of your gutters should be level (the short way) and not tipping away from the fascia of the structure, like in the gutter in the photo below. Think of a gutter as a container for water. If you hold the container at an angle, less water fits in the container. When you look at the gutters around your house make sure they are level (not tipping away from the fascia), if they are not level, they are likely not performing at full capacity and repairs may be needed.

2. Do not confuse #1 with "Proper Pitch" All gutters need to be properly pitched to ensure that water runs to the end with the downspout. Different gutter installers recommend different rates of pitch but the consensus among most installation professionals is that gutters should be pitched toward the downspout at a rate of 1/4" to 1/2" for every 10 feet of guttering.

3. The next issue to look for is clogged gutters and downspouts. You should arrange to clean your gutters twice a year. If the gutters are full of leaf debris, pine needles or shingle grit, the rain water fill flow over the edges of the gutters. When gutters overflow not only does it create the potential for moisture intrusion into your structure, it can have detrimental effects on the exterior siding and/or mechanical systems that are below the overflowing areas of the gutter system.

4. Downspouts are the next components that should be inspected for defects and clogs. The most common issues with the downspouts are: Clogged downspouts, loose and leaking joints, disconnected downspouts and finally, crimped or restricted elbows at the bottom of the gutter where the extensions are typically connected. If you find any of the conditions mentioned, gutter repairs may be needed.

5. And here we are, back at main topic of this post, downspout extensions. Downspouts should have extensions installed to prevent ponding, puddling and splash-back near the foundation. Extensions should be a minimum of 4 to 6 feet long, even if there is a noticeable slope in your grading that naturally directs water away from the structure. In some cases, longer extensions may be needed. Take my house for example; the grading around the house is relatively flat which requires me to have 10 foot extensions at most of my downspouts so that I can be assured that water discharged from the system will not end up in my basement.

6. My last bit of advice is to go outside in a good heavy rainstorm (yes, you might get wet) and look at the roof, gutters, downspouts, extensions and grading around your house. If you see water going somewhere you think it should not be going, you may need to take a closer look or have a professional take a look for you.

Building science is not always as straight forward as it seems that it should be. There are so many components of a house that must all be working in order for a house to function as designed. If any of those components are not functioning as intended there is a potential for accelerated damage or deterioration to those and other components of your house.

I have the experience, training and background to help you better understand your home. If you find yourself with a moisture problem at your house and you need help diagnosing the cause of the issue, call me at: 920-253-6278 or send an email to:

Disclaimer: Do not attempt anything in this blog post yourself if you are not familiar or comfortable with the required skills and abilities needed to perform any maintenance or repairs. Noble Inspections always recommends hiring a qualified professional for any maintenance or repairs.

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