Summary

Most domestic EV charger installations are straightforward: a wall-mounted charger fitted close to the consumer unit with a short first-fix cable run. But a meaningful minority — detached garages, charging posts positioned on a driveway away from the house, or properties where the consumer unit sits on the opposite side of the building from where the car is parked — need a buried SWA (steel wire armoured) cable run, and that is a groundworks job as much as an electrical one. Pricing this correctly matters because groundworks cost scales with ground type and surface finish, not with cable length alone, and getting it wrong either prices the installer out of the job or eats the entire margin on reinstatement.

The core pricing driver is what sits above the cable route, not the cable itself. A 10m run through a lawn is a half-day job with a spade and a narrow trencher. The same 10m run through a block-paved driveway requires lifting and storing the blocks, cutting a trench through the sub-base, laying the duct, backfilling to the correct compaction, and relaying the blocks to match the existing pattern — several times the labour and a material cost for sub-base reinstatement that the lawn job doesn't have.

This guide covers groundworks pricing specifically; for the electrical side of the installation (charger unit, consumer unit work, DNO notification) see ev charger pricing guide and domestic ev charger installation process.

Key Facts

Quick Reference Table

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Route Type Length Trenching Cost Notes
Lawn/border, short run 5m £175-£375 Hand-dig, turf reinstatement
Lawn/border, longer run 15m £525-£1,125 Mini-digger viable if access allows
Block paving, short run 5m £400-£750 Block lift/store/relay included
Block paving, longer run 15m £1,200-£2,250 More blocks to lift/store; higher labour
Tarmac driveway 5m £500-£900 Disc cut, cold-lay patch reinstatement
Tarmac driveway 15m £1,500-£2,700 Larger reinstatement area
Concrete driveway 5m £550-£950 Breaking out + concrete reinstatement
Mixed route (lawn + paving crossing) 10m total £600-£1,400 Priced per metre by surface type crossed
Public footpath crossing varies £800-£2,500+ Street works licence + reinstatement to highway authority spec

Detailed Guidance

Surveying the route before quoting

The single biggest cause of underquoted EV charger groundworks is pricing from a verbal description rather than a site visit. Before quoting, walk the actual route and note: total length, surface type at each section (lawn, border, paving, tarmac, concrete, gravel), any existing services likely to be crossed (run a CAT scan if there's any doubt), access for a mini-digger if the run is long, and whether the route crosses any area subject to vehicle loading. A route that looks like "15m across the garden" on a phone call can turn out to be 15m of which 4m crosses a block-paved patio — price each surface type separately.

Trenching process — soft ground

  1. Mark out the route and confirm no services present via CAT/Genny scan.
  2. Excavate to minimum 450-600mm depth, width sufficient for cable/duct plus hand clearance (typically 150-200mm wide).
  3. Lay 50mm of soft sand or sieved soil bedding at the trench base.
  4. Lay the SWA cable (or duct containing the cable) with gentle bends respecting minimum bend radius.
  5. Lay cable marker tape approximately 150mm above the cable.
  6. Backfill in layers, compacting as you go, reserving topsoil/turf for final reinstatement.
  7. Re-lay turf or reseed as agreed with the customer.

Trenching process — hard standing (block paving)

  1. Mark out the route and confirm no services present.
  2. Lift blocks along the route, keeping them in order where a pattern must be matched, and store safely.
  3. Excavate through the sub-base to the required depth.
  4. Lay bedding, cable/duct, and marker tape as per soft-ground method.
  5. Backfill and compact the sub-base layer (Type 1 MOT or equivalent) to match the original specification — under-compaction here causes a visible dip in the paving months later, a common comeback.
  6. Relay the sand bedding layer and refit the blocks, re-compacting with a plate vibrator and re-sanding joints.

Trenching process — tarmac or concrete

  1. Mark out and confirm no services present.
  2. Cut the surface cleanly with a disc cutter along the trench line to avoid ragged breakout edges.
  3. Break out and excavate to the required depth.
  4. Lay bedding, cable/duct, and marker tape.
  5. Backfill and compact the sub-base.
  6. Reinstate the surface: cold-lay tarmac patch (cheaper, faster, visible colour difference) or hot-lay/professional resurface (better match, higher cost, often subcontracted to a surfacing specialist); for concrete, pour and finish to match existing texture, allowing appropriate cure time before the area takes traffic.

Pricing the reinstatement standard explicitly

Always specify in the written quote exactly what reinstatement standard is included — "cold-lay tarmac patch, colour may not exactly match existing surface" is a very different promise to the customer than "full resurface to match." Disputes over reinstatement quality are one of the most common post-completion complaints on this job type, and a clear written scope avoids them.

Worked example — detached garage, mixed route

Job: 7kW charger on a detached garage, 12m run from the house consumer unit — 4m across a lawn, 5m across block-paved driveway, 3m across a short section of tarmac at the garage apron.

Frequently Asked Questions

Can I avoid groundworks cost by running the cable overhead instead of underground?

In some cases, yes — an overhead SWA run between buildings is permitted where the span, height clearance and support points are appropriate, and it avoids trenching cost entirely. However, overhead runs are rarely acceptable where the span crosses a driveway (vehicle height clearance, visual impact) or where the customer wants a tidy finish, so underground remains the default for most detached garage and driveway charger installs.

Do I need a street works licence to trench across a public footpath to reach a garage?

Yes, if the route crosses land outside the property's curtilage — a public footpath or verge — a street works licence (sometimes called a section 50 licence) from the local highway authority is required before digging, along with reinstatement to the authority's specification, which is typically a higher standard (and cost) than private driveway reinstatement. Always check this at quoting stage, as the licence process can add several weeks' lead time.

How do I avoid under-quoting the reinstatement on block paving?

Walk the route and count roughly how many blocks will need to be lifted, and check whether the existing blocks are a common pattern/colour likely to be relaid cleanly, or an older/discontinued style where exact joint-line matching will take longer. Always price reinstatement as a separate line so a harder-than-expected relay doesn't eat into the trenching margin.

Is 450mm trench depth always sufficient, or does it depend on the surface above?

450-600mm is the typical minimum for garden ground; increase to 600-750mm under any area subject to vehicle loading such as a driveway or parking area, and consider additional mechanical protection (a paving slab or duct) above the cable on vehicle-loaded routes. Always refer to BS 7671 Section 722 guidance and the cable manufacturer's installation instructions for the specific cable being used.

Regulations & Standards