Why Is My Basement Flooding?

Understanding Surface Drainage

Surface drainage is a critical aspect of home construction and maintenance. Ensuring water is effectively collected, managed, and directed away from the home prevents many issues, including foundation damage, basement flooding, and mold growth. The drainage requirements in the building code outline how surface water should be managed around a house. Let’s break down what this means and why it’s important.

Key Points of Drainage

Surface Drainage Diversion:

Requirement: Surface water around a residential building must be directed to a storm sewer or an approved collection point.

Purpose: This prevents water from pooling around the house foundation, which can lead to soil erosion, foundation damage, or moisture intrusion into the home.

Grading Around the Foundation:

Requirement: The ground surface around the structure should be graded to direct water away from the foundation. The ground should slope downwards from the house at a rate of at least 6 inches within the first 10 feet.

Purpose: Proper grading helps prevent water from accumulating near the foundation, reducing the risk of water seeping into the basement or crawlspace.

Exceptions to Standard Grading:

Physical Barriers: If barriers like lot lines, walls, or slopes prevent achieving a 6-inch fall within 10 feet, alternative drainage solutions must be implemented.

Drains or Swales: In such cases, drains or swales (shallow ditches) should be installed to ensure water is diverted away from the structure.

Impervious Surfaces: Surfaces like concrete or asphalt within 10 feet of the foundation must slope away from the building at a minimum rate of 2%.

Why Drainage Is Important

Prevents Foundation Damage: Water accumulation near foundation walls can lead to cracks and structural weakening.

Reduces Risk of Basement Flooding: Proper grading and drainage systems keep water from seeping into basements or crawlspaces, which can lead to costly repairs and potential health hazards from mold and mildew.

Protects Landscaping and Property: Effective drainage prevents soil erosion and protects landscaping, driveways, and walkways from water damage.

Quick Checklist for Home Inspectors

• Check Grading: Ensure the lot slopes away from the foundation with a minimum fall of 6 inches within the first 10 feet.

• Inspect Drainage Systems: Look for functional storm sewers, drains, or swales that direct water away from the home.

• Assess Impervious Surfaces: Verify that all concrete or asphalt surfaces near the home are sloped at least 2% away from the building.

• Identify Barriers: Note any physical barriers that could impede proper grading and confirm that alternative drainage solutions are in place.

By understanding and adhering to the drainage requirements, home inspectors can help homeowners avoid significant structural and water damage issues, ensuring a safe and healthy living environment.