10/01/2026
🎯 Purpose of the System
Prevent groundwater from coming into contact with the basement wall and drain water away before it creates hydrostatic pressure on the foundation.
🧱 Diagram Explanation (Top to Bottom)
1. Waterproof Barrier (red on the wall)
Bituminous coating or waterproof membrane
Prevents water from penetrating the wall
Primary protection against moisture
2. Exterior Wall Protection
Protective outer layer (often dimpled or drainage board)
Shields the waterproofing from damage
Helps guide water downward
3. Filtering Soil Layers (Top to Bottom)
🟤 Sand
First filtration layer
Prevents fine particles from migrating downward
Allows gentle water infiltration
⚪ Gravel
Speeds up drainage
Prevents water stagnation
🔵 Small Stones
Temporary water storage zone
Maintains high permeability
⚫ Large Stones
Highly permeable layer
Directs water efficiently toward the drain
4. Drain Pipe (Perforated Pipe)
Installed at the lowest point, next to the footing
Collects accumulated water
Channels it to:
a sump pit
a stormwater system
a natural outlet
5. Concrete Footing
Structural base of the house
Drain is placed alongside it to intercept water before it rises
💧 How the System Works
Rainwater infiltrates the soil
It passes through the filtering layers without pressure
The drain pipe captures the water
Water is evacuated before reaching the basement wall
👉 Result: Dry walls, a healthy basement, and protected foundations
✅ Advantages
Prevents water infiltration
Reduces pressure on foundation walls
Extends building lifespan
Limits mold and efflorescence
Proven, long-lasting solution
⚠️ Critical Installation Points
Proper slope of the drain pipe is essential
Geotextile fabric recommended around the drain (not shown)
Never backfill with fine soil against the wall
Periodic maintenance of outlets is necessary
🧠 Summary
This diagram represents the gold standard for foundation drainage.
It shows how to use gravity and permeable materials to keep a basement dry—even in wet soil
conditions.
