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 translates to a “slope” of 5 percent).
The EPA presents two ways foundations are compromised by poor drainage. These include “surface water from rain and snow that drains from the yard toward the foundation because of incorrect grading” and “water that drains from the roof and is deposited next to the home’s foundation instead of being carried away.”
The International Residential Code or IRC does require drainage “around all concrete or masonry foundations that retain earth and enclose habitable or usable spaces below grade.” This includes your crawlspace or basement. Well-draining soils may be the exception. However, if your area has expansive clay soil, proper foundation drainage is essential. Read more here: https://www.polymagic.net/foundation-repair-grading/