How important is Proper Grade or Slope?
As we all know, water runs downhill. That being the case we must give it a path that will
allow it to run away from the building or more specifically, away from the foundation. It
really doesn’t matter if you have a crawl space, basement, or slab-on-grade foundation
they all need proper drainage.
So, how do you tell if the slope/grade is correct? Over time and with experience you will
be able to look and see if it is a positive (away from the building) or negative (towards
the building) grade/slope. In the meantime, you can use either a 4-foot level or a ball
bearing (at least 3/4") to determine slope. Obviously, the ball bearing is only going to
work on hard surfaces like walks, drives, and patios. The level is for grass, landscape
The rule of thumb is for the grade to slope away from the building at the rate of about 1-
inch per foot for the first 6-feet. This is rarely the case in real life. We hope that it is at
least flat and not negative. Look for signs of puddling water, erosion or settling of the
soil near the foundation, and basement windows that are partially buried. All of these are
probable indications of improper slope/grade.
Now, even if the grade is correct the water running off the roof can wreak havoc on
the foundation as well. In homes with basements or areas with expansive soils, gutters should always be recommended to carry the water away from the foundation at least 4-6
feet. This will help tremendously with wet basements!
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