The best ways to improve foundation drainage typically involve sloping the ground around the structure and compacting the earth so that moisture is forced to the surface. While both are somewhat involved projects, they can usually be done relatively successfully without a lot of professional assistance. Owners should also regularly inspect gutters and other roof drainage systems, since improper draining can cause a lot of problems where foundational moisture is concerned. Planting certain bushes and shrubs near the base of a home or building might also help.
Why Drainage Is Important
Proper foundation drainage is an important consideration for homeowners, and any building owners for that matter. Regardless of the type and reliability of waterproofing that’s applied to the foundation, problems with the drainage can lead to water overwhelming the foundation, leaving the basement or crawlspace wet.
In addition to direct precipitation, there are two other ways that water can cause trouble. Underground water seeps into the area against the foundation, for one. Runoff from the roof also contributes more water than many people realize, and can often be the reason for a damp basement. Proper foundation drainage is relatively straightforward. It takes a little bit of planning, but is something most homeowners can complete on their own.
Sloping
The first step an owner or contractor should usually take is to make sure that the ground is sloped away from the home, so that the soil essentially runs downhill away from the foundation. This is most easily done as the house is being built, but can be performed with fairly good results later on, too. The main idea is to harness gravity to basically pull water away from the house. This will carry water away from the foundation, where it can then drain into the soil. The proper finished grade for the area around the home should usually be between ½ inch and 1 inch per foot (between 1.27 and 2.54 centimeters per 30 centimeters), extending away from the structure for at least 6 feet (1.82 meters), and preferably 10 (3.05 meters). The results aren’t usually noticeable; it doesn’t often look like a hill has been carved around the building. Still, even a slight grade can make a big difference.
Ground Compacting
Homeowners can also get good results by really compacting or compressing the ground around the foundation, particularly at the base of any slopes that have been created. In most cases this is easiest and most effective when done with a mechanical compactor. These sorts of machines will press the soil down with a lot more force than people could exert on their own, and soil compacted this way will be less likely to shift. Many home renovation stores or supply distributors rent these machines for temporary use.
If the soil isn’t pressed or compacted, it is possible for the force of water runoff — and the changing rate of settling that goes with it in most cases — to result in what’s known as a “negative grade.” When this happens, water will drain back to the foundation of the home. Ideally the soil should be compacted all the way around the perimeter, and should be repeated every few years to account for shifts and natural softening that happens with time.
Identify Soil Type
It’s also really important when thinking about both sloping and compacting to consider the main components of the surrounding earth, since the type of soil that is around the house has an impact on drainage. Soil that is heavily composed of gravel or sand will drain quickly, leaving little time for water to pool in the area. If the ground is made mainly of clay or other silts, though, it will more likely hold onto water and drain more slowly, which can lead to water pooling against the foundation underground. Long-term exposure to water can cause the foundation to eventually leak and crack. There is no easy way to change the basic composition of soil, but if the soil is composed of slow draining material, people should pay extra attention to other aspects of drainage.
Evaluate Gutters
Many homeowners are surprised to realize that water that collects on their roofs often has a direct impact on moisture in their foundation. As water runs off the top of a structure, it often flows downward in an inefficient way that can actually make things worse on and around the foundation. Most houses have gutters installed, but these aren’t usually enough on their own for adequate ground drainage. A typical gutter and downspout combination will lead water directly from the roof to the area right beside the foundation.
There are two ways to move water away from the foundation with this arrangement. The first is to use an extension at the base of the downspout, approximately 10 feet long (3.05 meters), that will carry the water away from the foundation and downhill. In these cases, the water won’t drain back to the foundation but will rather be shuttled away from the site entirely.
Using a catch basin is an alternative approach. A catch basin is a concrete basin buried at the point where the downspout ends. Filling the basin with crushed stone and attaching an underground drainpipe that comes out from the side of the basin can effectively force water out and away. That pipe should ideally run into an above-ground drainage ditch or empty into a drywell.
Other Preventative Measures
Taking measures to divert water away from the foundation of a home or other structure is usually the best way to improve drainage, but smaller remedial measures can also help, at least in the short term. Planting certain “foundation plants” like shrubs and succulent bushes to help absorb the water is one tactic, and is often leads to some success. Installing certain moisture-loving stones and yard features can also work, to an extent. In most cases, though, the most efficient way to keep a basement and foundation dry is to reduce the amount of water around the home in the first place.