On Closer Inspection: Maintaining proper slope.


When there are moisture stains on basement walls it is typically due to poor grading, short downspout extensions and or more costly, blocked/ broken drain tiles.

We see things differently depending on whether the stains are on our current home, or a home we want to purchase. When the stains are on our home, we often have the luxury of time to “properly” adjust the grade, extend the downspouts, clean up the basement walls, and wait to see if the staining returns. If it does, then there is a good chance that drain tiles are the problem. On newer homes it can also be a sump pump that is inoperable or just not set properly. Older homes may have seized palmer valves.

During a home inspection on a home we want to purchase, we don’t have the luxury of time and we know that repairing drain tiles can be much more expensive than a drain tile test. So we reduce our risk by having the test. Drain tile repairs are often $10,000 or more depending on the size of the home and the extent of the problem.

It’s great to get a clean bill of health after a drain tile test, BUT we now need to properly adjust and maintain the grading around the home.

The following section is from the exterior of the home inspection report on over 90% of the homes I inspect:

  • Adjust and maintain soils to slope away from the foundation at all sides of the home to provide a minimum drop of 1/2 inch for every foot away from the foundation to a point 10′ away from the foundation or to the lot line, whichever is less (SPS 321.12) to help minimize the risk of seepage and other water related foundation problems.
  • Adjust hard surfaces such as driveways, concrete walks, asphalt, etc. at all sides of the structure to provide a minimum drop of 1/4 inch for every foot away from the foundation. Swales will help direct water away from the foundation. Create swales within the first 5 feet of the foundation to help direct water away from softer loose backfill adjacent to the structure.

The reason we want to adjust and maintain the slope of the exterior surfaces adjacent to the home is to keep rainwater and melting snow from making the soils heavier, putting more pressure against the foundation walls and risk having the snow melt freeze and put over 100,000 pounds of pressure against the foundation which will often lead to wall movement and more costly repairs than those associated with drain tiles.

After properly adjusting the soils around the home, I recommend laying a 4 to 5 foot wide roll of rubber roofing material on top of the soils and cover it with lava rock or stone to keep the rubber from blowing away in the wind. This way rainfall and snow melt will drain away from the foundation rather than exert excessive pressure against the foundation which often results in expensive repairs.

Don’t take the results of a clean bill of health from a drain tile test to mean you are home free. All homeowners need to maintain that proper slope of grading around their homes.

Hope this helps!

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