French Drain Stone Calculator
Estimate the specific amount of stone needed for a french drain.
Proper Stone Selection
Use clean, angular crushed stone (3/4" to 1.5") like #57 stone for optimal drainage. Clean stone prevents clogging and maintains water flow capacity over time.
Trench Dimensions
Standard French drain trenches are 12-18 inches wide and 18-24 inches deep. Foundation drains may need to be deeper, matching the foundation footing depth.
Installation Tips
Wrap the perforated pipe in geotextile fabric, place it on 2-3" of gravel, and cover with 8-12" of stone. Proper installation ensures long-term drainage effectiveness.
Understanding French Drain Stone Requirements
A French drain is a trench filled with gravel or crushed stone containing a perforated pipe that redirects surface water and groundwater away from your property. Proper stone selection and quantity are critical for effective drainage performance.
Key Components of a French Drain
- Perforated Pipe: Typically 4-6 inches in diameter, collects and channels water away
- Clean Stone: 3/4" to 1.5" angular crushed stone provides drainage and structural support
- Geotextile Fabric: Wraps the pipe and lines the trench to prevent soil infiltration
- Proper Slope: Minimum 1% grade (1 inch per 8 feet) for water flow
Common French Drain Applications
Foundation Protection
Installed around building foundations to prevent water damage and basement flooding. Requires deeper trenches matching foundation depth.
Yard Drainage
Manages surface water in low-lying areas, preventing soggy lawns and standing water. Standard 18-24" depth is typically sufficient.
Driveway & Patio
Prevents water from pooling around paved surfaces, protecting against erosion and freeze-thaw damage. Often combined with base materials.
Related Calculators
For comprehensive drainage planning, you may also need:
- Drainage Stone Calculator - For general drainage projects and dry wells
- Landscape Stone Calculator - For overall landscaping material needs
- Driveway Stone Calculator - For driveway drainage and base materials
- Stone Base Calculator - For paver and patio base calculations
French Drain Stone Calculator - Calculate Gravel & Stone for Drainage
A French drain is an essential drainage solution for protecting your home's foundation and managing water runoff. Our French drain stone calculator helps you determine the exact amount of clean gravel or crushed stone needed for your drainage project. Proper material calculation is crucial for effective water management and preventing costly foundation damage.
French drains work by collecting water through a perforated pipe surrounded by stone, which allows water to flow freely while filtering out debris. The stone layer typically consists of 3/4 inch to 1.5-inch clean crushed stone, such as #57 crushed stone or drainage gravel. This calculator accounts for trench dimensions, pipe diameter, and proper stone coverage to ensure optimal drainage performance.
Whether you're installing a French drain around your foundation, in your yard, or along a driveway, accurate material estimation prevents over-ordering and ensures you have enough stone for proper installation. Our calculator also helps you understand the relationship between trench depth, width, and material volume, which is essential for landscaping projects and driveway drainage.
Frequently Asked Questions
What is the best stone size for a French drain?
The ideal stone size for French drains is 3/4 inch to 1.5-inch clean crushed stone. #57 crushed stone is the most commonly recommended size as it provides excellent drainage while preventing pipe clogging. The angular shape of crushed stone creates void spaces that allow water to flow freely, while the size prevents fine particles from washing into the pipe.
How much stone do I need per linear foot of French drain?
For a standard French drain trench that is 12 inches wide and 18 inches deep, you'll need approximately 0.5-0.7 cubic feet of stone per linear foot, or about 1.5-2 tons per 100 feet. However, the exact amount depends on your trench dimensions and pipe size. Use our French drain stone calculator with your specific measurements for an accurate estimate. The calculator accounts for the pipe volume and proper stone coverage above and below the pipe.
How deep should a French drain trench be?
French drain depth depends on your specific needs: 18-24 inches is standard for surface water drainage, while foundation drainage requires the trench to be at least as deep as the foundation footing (typically 24-36 inches). The pipe should sit on 2-3 inches of gravel with 8-12 inches of gravel covering it. Deeper trenches may be needed in areas with deep frost lines or when intercepting groundwater.
What does 'clean' stone mean and why is it important?
'Clean' or 'washed' stone means the aggregate has been rinsed to remove fine particles, sand, and dust. This is essential for French drains because fines would otherwise clog the void spaces between stones, impeding water flow and reducing drainage effectiveness. Clean stone maintains its drainage capacity over time, preventing system failure.
Do I need to wrap the French drain pipe in fabric?
Yes, the perforated drain pipe should be wrapped in geotextile filter fabric to prevent silt and soil from clogging the pipe's holes. The fabric acts as a filter, allowing water to pass through while blocking debris. Some pipes come pre-wrapped, but if not, you should wrap the pipe before placing it in the trench. The fabric should also line the trench sides in areas with fine soil.
Can I use pea gravel or rounded stone for a French drain?
While pea gravel allows water flow, angular crushed stone is preferred for French drains because its sharp edges lock together, providing better stability and preventing settling. Rounded stones can shift over time, potentially causing the pipe to move or the drain to become less effective. For foundation drainage and critical applications, always use angular crushed stone rather than rounded gravel.