How to Divert Roof Runoff Away from Your Foundation

Water is the single greatest threat to your home's structural integrity. When rain cascades off your roof and dumps directly against your siding, it saturates the soil at the base of your foundation. Over time, this hydrostatic pressure forces moisture through concrete, accelerates cracking, and invites basement leaks or mold growth. Doing this job well means creating a definitive, downhill path for that water to reach the lawn rather than soaking into your home's sub-grade components. Successfully managing runoff is less about complex plumbing and more about consistent physics. You are looking to achieve a slope that carries water away from the structure and disperses it safely into the yard. Once you eliminate that constant concentrated soak, you preserve your landscaping, protect your footings, and significantly lower the interior humidity of your home during the rainy season.

  1. Spot water pooling patterns. Observe your roof during a moderate rainstorm to identify where water currently pools. Measure the distance from the end of each downspout to the foundation wall to determine if you need simple splash blocks or full extensions.
  2. Clear the discharge zone. Remove any dirt, leaves, or mulch blocking the area where the downspout empties. Create a clear, flat surface on the ground where the new extension will sit.
  3. Position splash blocks. Position concrete or heavy-duty plastic splash blocks directly under the downspout outlet. Ensure the wide end of the block faces away from the house at a slight downward angle.
  4. Connect extension pieces. Slide the downspout extension over the existing elbow or outlet and secure it with two sheet metal screws. Ensure the extension is long enough to carry water at least six feet from the foundation.
  5. Build downhill slope. Build up the soil beneath the extension to maintain a consistent downward slope away from the house. Tamp the soil down firmly so it does not wash away during the next heavy downpour.
  6. Anchor the exit point. Place a decorative stone or a heavy brick at the exit point of the extension to hold it in place. This prevents the extension from being moved by high winds or heavy water pressure.