As a Houston home inspector, I see water damage and termite activity due to insufficient siding clearance from grade almost daily.
It is important to maintain proper clearance of your siding product from the soil grade level. This clearance is also called “foundation exposure” because the amount of concrete foundation we can see is determined by how far the soil grade level is below the siding. The more the better.
The reason for this is to prevent water intrusion into the structure due to ponding during heavy rains. Even the best drainage plan can be overwhelmed by Houston rains and we want the additional defense of adequate siding clearance. Also, the exposed foundation makes insect activity (termites, ants, etc.) much easier to detect.
The recommended clearance of masonry siding products (brick, stone, etc.) is 6 inches.
Wood siding clearance is recommended to be 8 inches from soil. Wood products need to be able to dry thoroughly after rain and the extra space aids that process.
Also, do not allow mulch (wood or stone) or vegetation to come in contact with any siding product.
And be especially vigilant regarding irrigation spray heads. Do not allow them to spray directly on siding products.