How to Grade Basements

Sloping the ground away from the house is essential for a dry basement.

Grading for surface drainage is one of the measures required to keep the basement dry. Concrete is a porous material, and runoff from rain and melting snow can penetrate basement walls if it collects around the foundation. Building regulations call for grading an apron around the foundation walls, sloped to a specified percentage to direct runoff away from the house. Grading requirements vary from region to region, and local building codes should be consulted before starting the work. Finish soft or hard landscaping can be installed on the graded surface.

Things You'll Need

• Well-drained gravel, crush or road mix type
• Skid steer loader
• Reversible plate compactor

Instructions

1. Remove soft soil and organic material within the area that's being graded around the basement wall. Replace with well-drained gravel, using the skid steer loader to place the gravel in 6-inch lifts, or layers. Compact each layer with the compactor.

2. Leave 8 inches of the foundation wall above grade. Grade the surface away from the wall, with a minimum 5 percent grade -- 3/4 inch drop per foot -- for at least 5 feet. Ensure that surface drainage flows away from window well, exterior stairs and decks.

3. Slope away from the house with a minimum 1 percent slope, where a patio or walkway is planned. Compact the ground well to establish a stable base for concrete or brick.

4. Direct the drainage toward a swale or ditch that carries runoff away from the house. Ensure only your own property is impacted by the runoff.

5. Spread decorative gravel or topsoil for sod or seed, or add hardscape features as desired. Maintain the established slope for the finish work.

Tips & Warnings

• Check with local building officials about required permits and approvals.

• Swales are shallow depressions, usually installed in the side yards and draining toward the street.

• Be careful with equipment close to the foundation walls to avoid cracking or other damage.

• Altering the drainage of neighboring properties is usually prohibited, and non-compliance may be subject to a fine.

Resources

• University of Tennessee: Wet Basement and Crawl Space Problems, Causes, and Remedies