Garden SurveyorDrainage Calculator
French drains, channel drains, soakaway crates, land drains and patio falls.
2 advanced inputs hidden. Switch to Advanced to fine-tune.
Order what you need for this job
MOT Type 3 (permeable sub-base) — bulk bag
Building Materials Nationwide
£35–£60 / tonne
See options
Heavy-duty weed-control membrane
Amazon
£15–£40 / roll
See options
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- Run length
- 10m
- Drainage type
- french-drain
- Perforated pipe
- 10m
- Drainage gravel
- 1.8t
- Geotextile membrane
- 15m²
Heads-up: Pipe falls matter more than pipe size: 1:80 minimum for foul, 1:40 for shallow surface runs. Too shallow and it silts; too steep and water runs ahead of solids. Why it matters: Connecting to a public sewer needs a Section 106 approval from your water authority.
Underground services check recommended before excavation. Use a CAT scanner or contact utility providers.
Why it matters: Gas, electric, water and telecoms cables are often shallower than expected — HSE guidance HSG47 mandates a safe-digging process.
If ignored: Striking a live service can cause serious injury, supply outages affecting the whole street, and personal liability for repair costs.
Matched to your spec. Partner links — we may earn a small commission if you buy, at no cost to you.
Essentials for this job
MOT Type 3 (permeable sub-base) — bulk bag
Building Materials Nationwide
Open-graded sub-base for SuDS-compliant permeable driveways and patios.
See options at Building Materials NationwideGuide price: £35–£60 / tonne
Indicative · reviewed May 2026
Clean stone 20 mm (drainage) — bulk bag
Building Materials Nationwide
Single-size clean stone for French drains, soakaways and pipe bedding.
See options at Building Materials Nationwide
Quantities include a ~10% waste allowance. Guide prices are indicative UK ranges (materials only, inc. VAT) — always confirm with the supplier before ordering.
Prefer to hire a pro?
Compare quotes from vetted local trades using this exact spec.
Ad · Some links are sponsored. We may earn a small commission at no extra cost to you. Suppliers are chosen for fit, not commission.
This app provides general UK guidance and material estimates only. It is not legal, planning, engineering or building-control advice. Always confirm requirements with your local planning authority, building control, utility providers, manufacturers or qualified professionals.