The guide
Cable trench sand bedding
A buried cable goes in a bed of compacted cable sand, is covered with more sand packed in by hand, then marked with warning tape and backfilled. How deep each layer is depends on the network operator and the voltage, so below are the operators’ own figures, with sources.
Last checked 2 October 2026. Always work to your own drawings and spec.
Step by step
- 01
Dig and trim
Dig to the depth and width on the drawings. Take out stones, flints and anything sharp from the bottom and sides.
- 02
Bed
Spread cable sand along the full width of the trench and compact it, so the cable never sits on stones or rubble.
- 03
Lay
Lay the cables or ducts on the bedding, with the spacing the spec gives.
- 04
Blind
Cover the cables with more sand, packed in by hand around the cables and joints so nothing is damaged.
- 05
Mark
Lay warning tape or cable tiles above the sand so the next person digging knows the cable is there.
- 06
Backfill
Fill to ground level in layers, compacting as you go, and reinstate the surface.
- 1BackfillDug-out soil or imported fill, as the job specifies.
- 2Warning tape or tilesMarks the cable for whoever digs here next.
- 3BlindingCable sand packed over and around the cable, by hand.
- 4Cable or ductLaid on the bedding, never on stones or rubble.
- 5BeddingA compacted layer of cable sand across the full trench width.
What the network operators ask for
Each operator sets its own rules for cables that will join its network. These are from the operators’ own documents. For every operator, area by area, see the areas we deliver to.
Northern Powergrid
North East, Yorkshire, northern Lincolnshire
- Low voltage, 11 kV and 20 kV: lay on the trench bottom only if it is smooth and stone free; otherwise dig 75 mm deeper and bed on smooth material such as sand. Blind with stone-free soil, selected sand or limestone dust to 75 mm over the top cable or duct, hand rammed.
- 33 kV to 132 kV: a 75 mm bed of selected sand or cement-bound sand, and blinding of the same to 75 mm over the top cable or duct.
- Special backfill around cables or ducts must be to ENA TS 97-1.
UK Power Networks
London, South East, East of England
- All bedding compacted to 75 mm across the full trench width.
- Blinding compacted to 100 mm over the cable.
- Low voltage and 11 kV: sand bedding at the bottom of the trench.
- 33 kV to 132 kV: a cement-bound sand bed to ENA TS 97-1 unless the rating calculations show it is not needed, and blinding with cement-bound sand.
SP Electricity North West
North West England (formerly Electricity North West)
- Surround material above, below and around the cables or ducts, at least 100 mm thick over the top for low voltage and 11 kV.
- Cement-bound materials are not used around low voltage and 11 kV cables unless approved.
- Minimum depth to the top of a low voltage cable: 0.45 m under footways, 0.60 m under roads, 0.90 m in good agricultural land.
Source: ES400E4, issue 12, June 2024
National Grid Electricity Distribution
East and West Midlands, South Wales, South West England (formerly Western Power Distribution)
- Bedding and blinding in crushed limestone or granite dust, 3 mm to dust, rather than sand.
- Blinded by 75 mm of the same over the cable or duct, before the warning tape.
Source: ST: CA6A/7, June 2021
NIE Networks
Northern Ireland
- Typical trenches: 1,000 mm deep by 400 mm wide across roads, 1,100 mm deep in farmland, 550 mm deep elsewhere.
- At least 50 mm of fine, compacted bedding and blinding, such as quarry dust or a similar soft material.
- The customer supplies the bedding, blinding and backfill.
Source: Connection specification for low voltage to multiple properties
Getting the sand right
Use clean, fine cable sand with no stones, clay lumps or rubble. On network work it usually has to meet ENA TS 97-1, with test results. Very dry sand is hard to compact, so dampen it if it arrives bone dry, and compact the bedding across the full width.
Work out how much you need with the cable sand calculator, which takes the ducts off. More on the sand itself in what cable sand is.
Questions
How deep should the sand be under a cable?
It depends on the network operator and the voltage. Northern Powergrid and UK Power Networks both work to a 75 mm compacted bed where sand bedding is needed, and NIE Networks to at least 50 mm. Your drawings and the operator’s rules for your area decide.
How much sand goes over the cable?
Northern Powergrid asks for 75 mm over the top cable or duct, and UK Power Networks’ 2015 rules for 100 mm, compacted. Take it from your spec.
Should cable sand be compacted?
Yes. Compact the bedding with a vibrating plate across the full width, and pack the blinding by hand around the cables and joints so nothing is damaged. Very dry sand compacts badly, so it may need dampening.
Can I backfill with the dug-out soil?
Above the sand and warning tape, usually yes, if it is free of large stones and the spec allows it. The sand around the cable itself should be clean cable sand or whatever the spec names.
Do these rules apply to a garden cable?
No. These are network operators’ rules for their own cables. A cable on your side of the meter, such as one to a garden office, follows the wiring regulations, so ask your electrician for the depth and protection.
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Bedding sand for your trench
Tell us how much, the site postcode and when. Usually next day on mainland Britain, from a single bulk bag.