French Drain Stone Calculator
Estimate the specific amount of stone needed for a french drain.
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Planning Your French Drain: A Deep Dive with Our Stone Calculator
A French drain is a highly effective solution for managing groundwater and preventing water damage to foundations, basements, and yards. At its core, it's a gravel-filled trench that contains a perforated pipe, designed to redirect water away from critical areas. Our French drain stone calculator is specifically designed to help you determine the exact amount of drainage stone needed for this vital project.
Success depends on using the right amount of the right material. The calculator takes your trench dimensions—length, width, and depth—and computes the volume of stone required to fill it. This ensures your system has maximum capacity for water flow, preventing overflows and ensuring longevity. Proper calculation saves money by avoiding over-ordering and ensures your drain functions correctly from day one.
Frequently Asked Questions
What is the best type of stone for a French drain?
The ideal material is clean, washed, angular gravel or crushed stone, typically 3/4-inch to 1.5-inches in size. #57 crushed stone is a perfect choice. The angular shapes interlock to hold the pipe securely, and the 'clean' nature ensures there are no fine particles to clog the system.
Do I really need to use geotextile fabric?
Yes, this is a non-negotiable step for a long-lasting French drain. The geotextile fabric lines the trench and wraps around the stone fill, acting as a filter to prevent soil, silt, and sand from entering and clogging your drainage system. A clogged drain will fail.
How deep and wide should a French drain trench be?
A common width is around 12 inches, which provides ample room for the pipe and surrounding stone. The depth depends on the application; for intercepting surface water, 18-24 inches is typical. To protect a foundation, the drain must be installed at or below the footing level.
How much stone is needed to surround the drain pipe?
Standard practice is to place a 2-3 inch layer of stone at the bottom of the trench, lay the perforated pipe on top (holes facing down), and then fill the remainder of the trench with stone to within a few inches of the surface. Our calculator determines the total volume needed for the entire trench.
How does this calculator determine the amount of stone?
It uses a simple volume calculation: Length × Width × Depth of your trench. It then converts this volume from cubic feet into the cubic yards and tons you'll need for ordering from a supplier, taking the guesswork out of the process.
Why is 'washed' gravel so important for a French drain?
'Washed' or 'clean' gravel has been rinsed of all fine particles like dirt and sand. This is critical because these fines would otherwise be washed into the gaps between your stones, clogging the system and severely reducing its ability to drain water.