Surface water, or water that collects on the ground after it rains or after snow melts, can flood a house’s basement and cause damage to the foundation. The slope of the ground around the house must be steep enough to drain water away from the foundation and basement.
How Grading Affects Drainage
Grading refers to the level of the ground around a house. Positive grading means the ground slopes away from the house and carries water away from the foundation. Negative grading means the ground slopes toward the house and carries water toward the foundation.
Sometimes soil settles, which results in improper grading. If the grading in the yard causes water to flow toward the house, it will accumulate at the walls, particularly around window wells, steps and downspouts. If your basement floods when it rains or your foundation is showing signs of water damage, changing the grading in the yard could solve the problem.
Does Your Yard Need to Be Regraded?
Take a walk around your house after a heavy rain and look for pools of water. If you see puddles near the house, the grading may need to be corrected.
The yard should have at least a 2 percent grade, or 1 foot of slope for every 50 feet of distance from the house. Insert stakes in the ground near the house and 50 feet away. Connect them with a string pulled taut and use a level to calculate the yard’s grade. If the ground slopes away from the house at less than a 2 percent grade, it needs to be corrected.
How to Regrade Your Yard
You might be able to regrade the yard yourself. Before you begin working, check the location of underground utilities and get a permit to dig if your city or town requires one. You can transfer soil from another part of your yard or purchase topsoil or grading soil to raise the level of the ground near the house.
The soil must be dense to divert water. Topsoil or grading soil will keep much of the water at grade level until it flows away from the house. Don’t use sand, since water could easily flow through it and damage the house.
Remove or add topsoil and subsoil as necessary to achieve the desired grade. When you pile soil near the house, be careful not to cover the siding, since that could attract termites. Till the subsoil and add fertilizer, then cover it with topsoil. Keep the depth of the soil as even as possible. Rake the topsoil so it’s smooth, then spread grass seed or sod.
Improve Drainage to Protect Your Home
If your basement floods when it rains, or if large puddles form near your house, the slope of the ground in your yard may be to blame. Changing the grading can be a simple but effective way to protect your foundation from water damage.