Standing Water and Drainage

Good Afternoon Friends,

I wanted to take a minute and remind everyone about standing water and drainage and mold prevention. With all the rain we are having it is really important that keep up on it. Please contact me with any questions. Please remember me for your Home Inspections, water testing, radon testing, mold test and remediation, termite treatments, and all your construction needs and much more.

Foundation Drainage


Foundation drainage refers to any system designed to divert or direct water away from a foundation. Such drainage includes systems installed outside the edge of foundations as well as systems that are installed under foundations.


In many areas the ability of soils to support a foundation is affected by the amount of water in the soils. Too much water can cause soils to be muddy, and a foundation can sink. Too much water, and expansive soils will lift a house up. Good foundation drainage helps to keep excess water away from a foundation and to prevent problems.


An hour after rain stops, do you have standing water within 10 feet of your foundation? If your answer is “Yes”, you may need drainage improvements.

Be prepared for when the rains come. Now is the time to review the drainage around the foundation. Proper foundation drainage helps prevent foundation problems. Cracked foundations are costly to fix while foundation drainage is a cheap and easy way to prevent foundation problems.

Help lessen the need for foundation repairs with a drainage swale or vegetated swale. Drainage swales are easy to install shallow ditches that drain excess water away from foundations. Often over looked and under used, drainage swales are simple and inexpensive foundation maintenance option.

Installs Gutters and Downspouts

These are the first things added as they are the easiest way to drain a foundation.

Adjust Slopes

The next step is, if possible, to slope the ground away from the foundation. Typically a slope of an inch a foot for 4 to 5 feet is adequate as long as water is not allowed to stand within 10 feet of a foundation.

Install Drains

If grading is not possible, area drains, drains that collect surface water are installed. In some situations, shallow French Drains are used as a solution.

Water Direction

Focus is to, when possible, direct water into a street, drainage ditch, or swale. A swale is simply a very shallow ditch that is used to carry off water.


Even when there is adequate exterior surface drainage water can flow under the surface and get under a slab. Based on how the water is flowing use the following approaches:

Install Moisture Barriers

Moisture barriers are vertical layers of plastic that are buried in the ground. As water flows up against a moisture barrier, it is stopped and prevented from getting under a home.

Install French Drains

French Drains are trenches filled with gravel that have a drain line buried in the gravel. French drains are designed to intercept and remove underground water.

Install Under Slab Drains

Rarely, it is necessary to tunnel under a foundation and install drains in the tunnels to collect and remove water. Drainage tunnels are dug by hand and typically measure 3 feet wide and 3 feet deep.

Keeping water drained away from home foundations is important for three reasons. First, if there is living space on the other side, the owner will want it to stay dry. Good drainage is the first step toward accomplishing that, then waterproofing. Second, soils supporting a foundation need to stay at a consistent moisture level to prevent settlement, heave, or differential movement. Last, but not least, drains are required by the building code. Here are a few things to keep in mind:

Moisture: There are two zones of subsurface moisture: the aeration zone (where both water and air exist) and the saturation zone. Generally, the saturation zone is everything below the water table, which is the level at which water rises to in a well. The saturation zone is seldom an issue in residential construction—soil moisture is the concern.

Loss of soil moisture: Soil moisture beneath a foundation is lost in a triangular configuration, so the deepest dry area is just outside the edge of the foundation and the ground beneath the middle of the slab remains saturated. Differential drying or differential amounts of moisture in the soil can create problems, especially in expansive soils, which in many parts of the country are more the rule than the exception. In some areas, homeowners actually have to water their foundations to maintain soil moisture.

Surface drainage: Controlling surface water is critical to controlling soil moisture beneath the foundation. The ground surface should slope away from the house at between ½ and 1 inch per foot for at least 6 feet—10 feet is better. Be careful of poorly compacted backfill, though, because that will soon mean that the surface will slope back toward the house.

Gutters: Downspouts should discharge on sloping surfaces at least 10 feet from the foundation. Where that isn't possible, downspouts should discharge into drained catch basins.