Renovation & Design

Drainage slope away from foundation always prudent

Question: I read your recent article in the Free Press about how to properly maintain the slope away from the house. I would like to ask you a question and will appreciate your answer. I did understand that the best is to use clay, but it is not available in landscaping stores. What would be my additional techniques to create a slope, to drain water away from the house, using materials that are commonly available? Can I use quarter down? Or can I just use topsoil and an additional layer on top, to prevent the soil from being washed away?

Thank You in advance,

Vadim N.

Answer: Building up the soil adjacent to your foundation is an easy and important way to prevent typical basement leakage. Using topsoil from a local landscape supplier is fine as long as you take proper measures to prevent erosion and washing away of the soil.

The heavy clay-based soil in our Red River valley area may be problematic for house foundations due to its expansive properties when saturated. Fortunately, that same property makes it very good for creating good grading around our homes. Having a well-draining substrate below grade adjacent to the foundation is ideal, but maintaining a “clay cap” at the top of the soil will help shed water efficiently. Because the clay can only absorb a certain amount of water before becoming saturated, it will help with runoff from heavy rains and melting snow when very wet. This will help prevent excess moisture up against the foundation walls below grade, as long as good grading practices are in place. If the grade is sloping toward the house, clay at the top of the soil column will do the reverse and shed water in the wrong direction, and can be a direct cause of moisture intrusion, instead.

Even though heavy clay soil is not normally available at retail stores, it can often be obtained nearby, with a little creativity. Anywhere there is construction activity that requires digging, clay soil will be in abundance. This should hold true where a new home or building is going up, due to excavation for the basement. It may also be piled up on the street from a foundation repair, pool installation, or even from drilling holes for new fence posts. Most contractors will have to pay to take this unwanted material away, so they may be thrilled if you offer to remove some for use at your own home. If it is close, using a long-handled shovel and wheelbarrow may be all that is required. If it is further away, a small trailer will be a better choice, even if it has to be rented on a short-term basis from a U-Rent retailer.

Working with clay soil, especially if it is wet, can be difficult and will require patience and strength. It is not very easy to spread against your house, but is easier when dried out. If you are able to get a sufficient quantity for your job, piling it up reasonably well may be all that is required. Once in place, even if it is lumpy and uneven, the process can be completed by finishing it off with typical topsoil. That will allow you to smooth the surface, allowing for better runoff, and will also ensure the next step works well. Planting grass seed, or sod if available, will help to stabilize the soil and prevent erosion. If the area will not easily grow grass due to lack of sunlight or moisture, adding a thin layer of bark chips, mulch, or stones may also prevent loss of the soil, over time. Installing a landscape fabric over the sloped topsoil, before the other materials, may also help prevent unwanted weeds from poking through.

If this all sounds like too much effort, or you simply can’t find a source of ugly clay, completing the entire job with topsoil is your next best bet. Topsoil will be much easier to work with and easier to smooth out for a good sloping grade. Using a lawn roller, or small compactor, can also aid in those efforts and prevent dry soil from blowing away. The roller is also an effective way of ensuring that grass seed applied on top of the newly sloped area is evenly spread. Going over the area another time or two after spreading the seed will embed it in the soil and prevent loss from the elements and feeding birds. The final step is to water the area immediately after completion, and very regularly thereafter, as long as it does not rain too much.

It is possible to apply another type of granular fill, like the quarter down you mentioned, but that is not as reliable for several reasons. Firstly, it may shed water fairly well when wet or compacted, but is not easily maintained in a proper slope. You can’t grow anything on top, unlike the soil, so it may wash away or erode much more easily. It will also collect dirt and debris, and can become covered with unwanted weeds.

Piling up clay and topsoil against your foundation walls, to provide a good drainage slope, will be your best bet for a dry basement. Ensuring the slope is smooth, covered well with grass or other low vegetation, and watered regularly, are the final pieces of the puzzle for good water management.

Ari Marantz is the owner of Trained Eye Home Inspection Ltd. and a Registered Home Inspector (RHI)( Questions can be emailed to the address below. Ari can be reached at 204-291-5358 or check out his website at


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