What can I do if my lot isn't graded properly?

MMH Expert_Matt T EXPERT April 24, 2008

Where the grading is flat or slopes toward the building, improvements to the grading are probably necessary. Look for water damage at the exterior wall, where water may be collecting against it, and inside the building.

Causes include

• inappropriate landscaping work.
• erosion of garden soils by rain, often resulting from missing, leaking or overflowing gutters and downspouts. It is common to find a low area where a downspout leaks or a gutter overflows at a corner.
• the compaction of backfill after original construction.

In houses with continuous perimeter foundations, the disturbed soil adjacent to the house is backfilled after construction. Even if this backfill is well compacted, the soil close to the building may settle for the first year or two after construction. The deeper the foundation, the greater the settlement, typically. Although the builder may create a finished grade that provides good drainage initially, this settling backfill can create an improper slope.

The implications of poor lot grading are

• wet basements and crawlspaces
• damage to foundations
• damage to siding material, in severe cases

To check your lot grading, look at the slope of the grade around the entire building and consider the paths available for runoff. If you can't see any slope, it's suspect. Consider the soil conditions if you have any knowledge of them, and consider whether the surface materials are free-draining.

You may need to consider improving the grading. This often involves the addition of topsoil. Resodding may be needed as well. Remember that dirt cannot be piled against siding. There may not be enough space between the existing grade and the top of the foundation to allow enough soil to be added to change the grade. In this case, other measures will be needed.

Regrading sometimes brings soil levels up to basement windows. Window wells may be needed to protect windows and their frames from contact with the soil.

If the land over a large area (the entire backyard, for example) slopes toward the house, a swale should be considered. Contractors often recommend digging and dampproofing. The excavation of driveways, sidewalks, patios, gardens, shrubs, trees, etc., is disruptive and expensive. A swale several feet from the building is often a better answer than a disruptive excavation project. The swale may be designed to direct water around the home and down away from the building. When the site doesn't allow this, one or more catch basins in the swale may be necessary.

In other cases, one or more catch basins without swales may be the best alternative, although they are expensive. Catch basins can drain either into a storm drainage system or into a French drain. A French drain is an excavated hole that is filled with gravel. Water from the catch basin drains into the gravel in the French drain, where it accumulates until it leaches into the soil. The French drain should be far enough away from the house that the saturated soil around it does not affect the foundations. In climates where the soil freezes, catch basins must be designed to withstand the forces of frost.

Where water accumulation against the foundations can't be prevented, the only solution may be excavating around the house, adding or repairing tile, and dampproofing the foundation wall before backfilling. This is the most expensive approach. Many specialists also recommend using a drainage material against the wall. This keeps soil away from the wall, and allows water to fall freely to the drainage tile.

Watch for downspouts from neighboring homes that discharge onto your property. Missing, leaking or clogged gutters on adjacent houses can also dump water close to your home. Are swales or naturally sloping lots on neighboring properties directing water onto your lot? Many municipalities prohibit discharging runoff onto adjacent properties, within reason. Check your local rules on this issue.