Gutters and downspouts play an important role in managing rain water around your house. When configured properly, they effectively direct roof water away from your home. When they are not, large amounts of water are allowed to dump next to your foundation causing seepage and even worse, foundation movement.
In our area, where many foundations are surrounded by an expansive soil like clay, balancing ground hydration is critical. During dry spells, too little water can dry out clay causing it to shrink and crack. Then the weight of house foundations sitting on the clay compress those cracks and movement occurs. Fortunately our dry spells aren’t as frequent as say, Houston, Texas where residents regularly water the ground around their foundations to keep their clay moist.
Too much moisture can also be a bad thing. During our wet season, the soil surrounding basements gets oversaturated. Around shallow foundations like attached garages, room additions and crawl spaces, this oversaturation softens the ground beneath the foundation and the weight of the structure sinks because the ground it’s resting on turns to mud. On deeper foundations, the oversaturated clay next to them expands, pushing against the foundation walls causing cracking and bowing.
That is why it’s important to learn about water from downspouts. Controlling it is essential to balancing the hydration of the ground around your foundation.
FACT 1) On a house with a 1000 square foot roof, 1 inch of rain feeds 623 gallons of water into the gutters and downspouts. If that roof empties into 4 downspouts that aren’t extended, then each one is spouting 150 gallons of water right next to the foundation.
FACT 2) Rain barrels hold about 50 gallons of water. So the 623 gallons mentioned above would easily fill 12 of them. Most houses with rain barrels usually only have one or two. Where does the rest of that 150 gallons of water go? You guessed it - next to the foundation.
FACT 3) So far we’ve been talking about 1 inch of water, but in Chicagoland the annual rainfall averages almost 37 inches! That means it's possible the water from downspouts at a single house is contributing over 23,000 gallons to the home's Zone of Failure. It’s no wonder so many of our foundation walls are sinking, cracking and bowing.
FACT 4) During a heavy storm the velocity of water rushing out of the downspout is equal to a bathtub filling at full blast. Research has found that typically 67% of home downspouts are either partially or completely clogged with leaves, dirt or going into a pipe to nowhere. If the roof water can’t get through the downspout, it backs up, spills over the sides of the gutters and right next to the foundation.
FACT 5) As we’ve just learned, downspout water dumping next to houses is a primary contributor to basement seepage and a major cause of foundation structural issues. We’ve also learned there are many reasons roof water unintentionally ends up next to foundations. So here is the most important fact of all. Downspout water can be effectively controlled for pennies, compared to the dollars required to repair the foundation damage caused if the water from downspouts isn’t proactively controlled.
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