🏡 What is a French Drain? A UK Guide to Solving Garden Drainage Problems
A French drain is a simple yet powerful underground drainage system designed to redirect surface water or groundwater away from specific areas — often used in UK gardens to prevent waterlogging, protect foundations, and improve lawn health.
If your garden puddles after rain or you’re battling a soggy lawn, installing a French drain pipe could be your perfect fix.
🛠 What You Need to Make a French Drain:
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Perforated land drain pipe (flexible or rigid)
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Landscaping fabric (geo-textile membrane)
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Gravel or aggregate
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Shovel or trenching tool
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Spirit level
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Wheelbarrow
📏 How to Install a French Drain (Step-by-Step)
✅ Step 1: Plan Your Drainage Route
Find the lowest point in your garden where water collects. From there, plan a gentle slope (1% fall) to direct the water away — ideally to a soakaway or a drain.
✅ Step 2: Dig the Trench
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Depth: Around 450–600mm
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Width: 200–300mm
Use a spirit level and line to maintain a slight slope for gravity-assisted drainage.
✅ Step 3: Lay Fabric & Gravel
Line the trench with a permeable membrane to prevent clogging, then add a base layer of gravel (approx. 50–100mm deep).
✅ Step 4: Install the French Drain Pipe
Lay the perforated French drain pipe on top of the gravel with holes facing down. This allows water to enter from below and disperse through the pipe.
✅ Step 5: Add Gravel and Wrap
Cover the pipe with more gravel, stopping about 50mm from the surface. Fold the membrane over the top of the gravel to seal.
✅ Step 6: Backfill and Finish
Add soil or decorative stones over the top. You’re done! You’ve just installed a French drain system that should last decades.
🔍 How Does a French Drain Work?
A French drain works by:
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Collecting water through perforated pipe holes
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Dispersing it away from problem areas
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Preventing saturation of garden soil and structures
It’s especially effective in clay soil gardens where water doesn’t easily drain.
🌧 French Drain UK Applications:
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Garden drainage
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Waterlogged lawns
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Wet driveways
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Foundation protection
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Behind retaining walls
📐 French Drain Calculator
French Drain Calculator
Estimate how much pipe, gravel, and membrane you need for your French drain system.
To learn more about effective garden drainage, check out this Royal Horticultural Society guide, read Marshalls’ landscape drainage tips, or explore this DIY Network French drain tutorial. Ready to protect your new build home from water issues? Book your professional drainage survey with New Homes Inspections today.