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Why your basement leaks and what to fix

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1The volume of water involved is bigger than people expect

A single 1-inch rain drops 1,250 gallons of water onto the roof of a 2,000-square-foot house; without grading, gutters and downspouts doing their job, some of that volume ends up right at the foundation instead of away from it.

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2A downspout without an extension can be worse than none

A downspout that dumps water right at the foundation, with no extension or splash block, concentrates a huge volume of roof runoff in one spot near the basement wall; the fix is a minimum of one downspout per 50 linear feet of roof eave, with extensions discharging water at least 4 feet beyond the wall.

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3A dehumidifier bought first can make things worse

Running a dehumidifier in a basement that still has an active moisture problem can pull moisture into the basement more rapidly, causing efflorescence and spalling of concrete and further damaging interior finishes; it manages a symptom, and only after the actual water source is addressed.

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4Inspect for the actual leak before sealing anything

Basement walls and floors should be checked for cracks or breaks that can turn into active leaks, especially where walls meet, since that's where seepage is most common; the lower a basement sits in the ground, the more pressure its walls feel from incoming water, and older homes are more vulnerable as foundations settle over time.

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5Radon is the basement's other moisture-adjacent problem

EPA estimates nearly 1 in every 15 U.S. homes has an elevated radon level, 4 picocuries per liter or more, the point at which EPA recommends fixing the home; radon enters the same way ground moisture does, through cracks and gaps in the foundation, and basements are where levels are typically highest since that's the floor closest to the soil.

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