It’s probably safe to say that most people realize that the one element that can be the most damaging to a house is water. From the top of the roof to the foundation, the exterior building materials that your house is constructed with are designed and install in a manner to protect it from water damage.
One area of the house that can be troublesome for homeowners is the basement. Excess water around the outside of a house can lead to a wet basement, musty odors, and even mold and mildew. Keeping a basement dry can be accomplished by directing the water on the outside of the house far away from the foundation / basement walls.
If you have a wet basement, there are some things you can do outside your house to help keep your basement from getting wet, or keep excess moisture away from the walls. Basement walls are typically built using poured concrete or concrete block, and concrete can absorb water and wick moisture from the outside to the inside of the wall.
Simple Things You Can Do First
There are relatively simple, but important, things you can do to the average lot. First, keep your gutters in good shape and flowing properly. An overflowing gutter can cause leaks in the basement in the area(s) where the overflow occurs. If your downspout empties out into your yard, the end of it needs to be far away from the house. A downspout could also be connected to a solid drainage pipe that runs either to daylight, a dry well, or out to the street. Many communities require that gutters be piped out to the street gutter.
Typically, splash blocks that empty into a lawn or planting bed do not move rainwater far enough away from the foundation walls. The outside of the foundation wall is backfilled with coarse gravel and has lots of voids (space) between the stones. Water near the basement walls will find these voids because water travels to areas of least resistance.
The second thing you can do is to make sure the ground around your house is sloped away from the house. This may sound too simple to make a difference, but it is a simple theory – water runs downhill (and away from the house) every time! Adding soil around your foundation to regrade for better drainage may require using a window well of some type for your basement windows.
Slope is Important
If your yard has enough pitch to it, you will be able to slope the grade around the house. The minimum slope should be 5%, which translates to 6 inches of slope in the first 10 feet away from the foundation wall (some communities have specific code requirements for slope). To create a slope to direct water away from the house, use soil that does not contain organic material, sand, or other amendments. This type of soil is too loose and does not compact well (great for the garden, not great for drainage issues). The more it can be compacted (a hand tamp can be use for this), the more water can be divert from the foundation walls.
In some areas around your house there may be walks, steps, and other things that make it difficult to grade around for drainage reasons. Even a yard that is extremely flat can be challenging. These situations may require other drainage solutions, such as digging a trench for drainage pipe, gravel, and filter fabric.
As a last note, be sure when you are landscaping and mulching near the foundation that you are not creating a future problem where rainwater or water from the hose and sprinkler will collect up against the walls.
If you are experiencing dampness in your basement, check your gutters (we have actually seen gutters that were so full of debris that there were plants growing in them! Yikes!), and make sure the grade around the house has the proper slope to take water away from the foundation walls. And then wait for a few good rainfalls to see if there is an improvement in the condition of the basement walls along where you were able to create or increase slope outside.