Yard grading is a fundamental process designed to manage surface water runoff and protect the structure of the house. This technique involves reshaping the soil around the foundation to create a slope that directs rainwater and snowmelt away from the building. The primary objective is to prevent water from pooling near the perimeter, which is a leading cause of structural deterioration. Achieving the correct slope safeguards the home’s long-term stability and prevents costly water damage.
Why Proper Slope is Essential for Foundation Health
Water pooling near a home’s foundation is a significant threat because it leads to hydrostatic pressure. This pressure is the force exerted by water-saturated soil against the foundation walls. When the soil becomes waterlogged after heavy rain or snowmelt, the immense weight and expansion push inward on basement or crawlspace walls. Over time, this constant force can cause structural damage, including horizontal or vertical cracks in the foundation walls.
The pressure can force water through fissures in the concrete, resulting in basement leaks, dampness, and flooding. Water intrusion creates an environment conducive to mold and mildew growth, while also contributing to the breakdown of the concrete itself. Maintaining a consistent moisture level in the soil surrounding the foundation is important to minimize movement, especially in areas with expansive clay soils that swell when wet and shrink when dry. A correct grade mitigates these risks by ensuring water moves away from the structure immediately.
Determining the Required Grade and Marking Guidelines
Proper grading requires a minimum slope of six inches of drop over the first ten feet extending away from the foundation. This equates to a five percent slope, or approximately a half-inch drop per foot. While a steeper slope is generally better for drainage, a lesser slope of one-quarter inch per foot may be acceptable for paved areas like patios and walkways. The goal is to ensure all surface water flows continuously away from the house.
To establish this guideline, a homeowner can use wooden stakes, nylon string, and a line level or laser level. Begin by driving a stake into the ground about a foot away from the foundation at a corner of the house. Measure out ten feet directly away from the house and drive a second stake into the ground at that point. Attach the nylon string to the first stake near the foundation, securing it at the desired height of the final grade.
Attach the line level to the string and pull the string taut to the second stake, then adjust the string’s height until the bubble on the level indicates a perfectly level line. This level line represents the zero-drop point over the ten-foot distance. To determine the target six-inch drop, measure down six inches from the level string line at the ten-foot stake and mark this point. This mark establishes the required grade line for the entire ten-foot span, and this process should be repeated around the entire perimeter of the house.
The Physical Process of Reshaping the Yard
Before adding any new material, prepare the area by removing existing landscaping, mulch, or any excessively high soil that is currently sloping toward the foundation. It is also important to contact the 811 utility notification center before digging to ensure no underground lines are disturbed. The most suitable material for regrading is a screened fill dirt, specifically a silty clay loam, which offers a balance of stability and semi-permeability. This type of soil compacts well, helping to prevent future settling, while still supporting vegetation growth.
If a significant amount of soil is needed to achieve the six-inch drop, the fill dirt should be added in layers, with each layer being mechanically compacted, or tamped, before the next is added. Compacting the soil is necessary to prevent the new grade from settling unevenly over time and reversing the slope toward the house. Using the string line guidelines, shape the soil with a shovel and rake to create a smooth, continuous incline away from the foundation. Maintain a minimum clearance of six to eight inches between the finished grade and any wood or siding components of the house. This separation is required to allow the siding to dry properly and to keep wood-destroying organisms like termites from gaining easy access to the structure.
Finalizing the Grade and Protecting the Soil
Once the desired slope is achieved and the soil has been shaped, the final step involves thorough compaction to solidify the new grade. Compacting the soil, either with a hand tamper or a plate compactor for larger areas, minimizes the risk of the soil settling unevenly after the first few rain events. Uncompacted soil will inevitably settle, potentially reducing the critical slope and compromising the water management efforts.
Immediate measures should be taken to protect the newly graded soil from erosion, which can quickly wash away the carefully shaped grade during heavy rainfall. The quickest solution is laying sod, but applying grass seed or spreading straw over the exposed soil will also stabilize the surface. When considering landscaping near the foundation, avoid heavy mulches or porous materials like gravel that hold moisture against the foundation wall. Instead, maintain a clear space or use a non-porous material to ensure the foundation remains dry and protected.