The consensus seems to be that a good slope to aim for when grading land extending out from a house foundation is about 6 inches for the first 10 feet (that's a slope of 5 percent). Many professionals grade land successfully using a lesser slope than that; but those who wish to be on the safe side err on in the direction of greater slope.
But how do you find the slope of a stretch of land, to begin with (so you'll know if the slope needs to be adjusted)? Rather than boring you with a fancy formula with "X" and "Y" in it, used to determine slope, let's take more of a hands-on approach to land grading.
To find the slope away from your foundation, you'll need
- String (at least 12 feet long)
- 2 stakes, and something to pound them into the ground
- String level
- Tape measure
How Much Slope?
Using the above supplies, take the following steps to determine if sufficient slope currently exists:
- Tie one end of the string loosely around stake A.
- Pound stake A into the ground right near your foundation
- Slide the string down stake A, so that it rests at ground level
- Tie the other end of the string loosely around stake b.
- Now measure out 10 feet down the slope from stake A, and pound stake B into the ground there (if there's excess string, just wrap it around stake B). The string between the stakes should be fairly taut, but still adjustable.
- Slide the string up or down stake B, so as to make it roughly level.
- Put the string level on the string, at about the mid-point between the stakes.
- Now adjust the string up or down on stake B, so as to make it exactly level.
- Measure the distance from the string on stake B to the ground. Is the measurement 6 inches or more?
Do You Need to Re-Grade the Land?
The slope measurement you just took will determine whether or not you need to re-grade this land:
- If the measurement is 6 inches or more, you have a perfect slope -- no need for land grading here!
- If not, you'll need to re-grade the land by adding fill near the foundation and tamping it down; after which you can check the new slope by repeating the steps above.