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How to Stop Water From Entering the Basement

Basement moisture can lead to the development of unpleasant odors and harmful molds and, in severe cases, cause structural damage and greatly impact the appeal and value of a structure. Sometimes, preventing or correcting a wet basement is as simple as clearing debris from a clogged gutter or extending a problematic downspout. In more serious situations, correcting the slope of the surrounding landscape or installing a foundation drain is required.

Gutters and Downspouts

Some of the easiest causes of basement moisture to address are problems related to gutters or downspouts. Regular gutter and downspout inspection and debris removal addresses clogs and overflowing water that could be running down the house next to the foundation and entering the structure. Excessive water flow spilling over gutters could warrant the installation of additional downspouts. Downspouts should extend at least 10 feet from a house. A splash pad at the end of each downspout may also help to direct and disperse water.


A surrounding landscape that slopes toward the structure can easily direct water to the foundation and cause penetration. Re-grade the landscape, if possible. Fill in any depressions or low spots against or near the structure but maintain adequate space between the ground and any wood siding or stucco on the structure. Where the slope is too great to adjust, a ditch or swale provides an option to direct water around the house or to a specified channel. Changing the slope of the landscape may not be feasible where space is limited or there are other restrictions.

Exterior Drainage System

An exterior drainage system is often the most expensive or time-consuming exterior drainage solution to implement, but it also the most effective solution. Exterior drainage system installation involves digging a trench next to the structure that extends to the depth of the footing or less deep, when the water runoff is primarily a surface concern. The trench must lead to a sump pump, ditch or other suitable outlet. A 4-inch, perforated drain pipe is placed at the bottom of the trench, covered with a thick layer of coarse, clean gravel and topped with filter fabric before the remainder of the trench is filled with free-draining backfill.

Exterior Foundation Waterproofing

Often, a waterproofing layer is added to the foundation exterior at the same time an exterior drainage system is installed. The exterior wall surface is cleaned and multiple layers of an asphalt or tar coating is painted on to act as a basic vapor retarder. Where water entry is more problematic, a plastic vapor-retarding membrane is warranted. The waterproofing or vapor-proofing membrane is often protected by a protection board or rigid insulation.

Interior Drainage Systems

In some situations where the landscape cannot be altered or space constraints limit the type of outdoor work that is feasible, an interior drainage system is necessary. The simplest type of system incorporates fastening a channel to the floor slab at the base of the wall to capture water and direct it to a sump pump. More intensive interior drainage systems incorporate breaking up the floor slab around the edge and installing gravel and a perforated drain pipe that directs water to the sump basin before placing new concrete on top of the gravel and pipe.

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