1. What is Rock for French Drain?

Rock for French drain refers to the amount of drainage rock needed to fill a french drain trench, accounting for the 40% void space that allows for proper water flow and drainage.

2. How Does the Calculator Work?

The calculator uses the simple equation:

Where:

• \( Rock \) — Amount of rock needed (cubic feet)
• \( Trench\ Volume \) — Total volume of the trench (cubic feet)
• \( 0.4 \) — 40% void space factor

Explanation: The equation accounts for the void space needed between rocks for proper drainage in a french drain system.

3. Importance of Proper Rock Calculation

Details: Accurate rock calculation ensures proper drainage capacity while minimizing material waste and project costs.

4. Using the Calculator

Tips: Enter the total trench volume in cubic feet. The volume can be calculated as length × width × depth of your trench.

5. Frequently Asked Questions (FAQ)

Q1: Why 40% void space?
A: 40% void space provides optimal balance between water flow capacity and structural stability of the drain.

Q2: What type of rock should I use?
A: Use clean, washed gravel or crushed stone (typically ¾" to 1½" in size) that won't compact over time.

Q3: How do I measure trench volume?
A: Measure length × width × depth in feet, then multiply these dimensions together to get cubic feet.

Q4: Should I add extra rock?
A: It's recommended to add 10-15% extra to account for settling and variations in rock size.

Q5: Can I use this for other drainage systems?
A: This calculation works for similar drainage systems, but specific requirements may vary.