Screw pile underpinning
Steel helical piles screwed into the ground to a tested depth, then connected to the structure with brackets or a beam.
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- 20 year remedial warranty
- Diagnostics to remedial work
What it is
Screw piles are steel shafts with one or more helices welded near the tip. A torque motor drives them in until the design resistance is reached. The depth and capacity are confirmed in real time from the torque reading, which is one reason engineers like them.
Because there is no excavation and no concrete to cure, screw piles can carry load almost immediately after installation. That is unusual in foundation repair and is the main reason they get specified for time-critical jobs.
Galvanised steel shafts and helices are typically 75–150mm in diameter for residential underpinning. Brackets connect the pile head to the existing footing, or a small reinforced concrete beam ties multiple piles together.
When it's used
Screw piles fit lighter structures and time-critical jobs: porches, conservatories, single-storey extensions, garden rooms, and remedial work where the property cannot tolerate weeks of disruption. They are the right answer where there is no room to store and pour concrete, where soft alluvial or made-up ground sits above a competent layer that the helices can find, and where the load needs to come on almost immediately. We also use them as preventative foundations for new extensions on tricky ground, because the torque reading confirms capacity in real time and removes a lot of the guesswork that comes with pouring concrete into a hole and hoping.
Screw piles are not a universal answer. Dense gravels, cobbles, and old building foundations stop the helices, and obstructions are common in urban back gardens. Heavier loads, three-storey terraces and above, usually push the engineer toward mini piles instead. Insurer familiarity is improving but still patchy, so on insurance-led work it is worth checking the loss adjuster will accept the method before specifying it.
How the work runs
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1. Torque test pile
A trial pile installed first to confirm depth and capacity.
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2. Production piles
Remaining piles installed to matching torque values.
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3. Connection
Brackets or a small capping beam tie the piles to the wall or slab.
Pros and cons
Pros
- Immediate load capacity, no concrete cure time
- Minimal spoil and very little disruption
- Real-time capacity verification from torque
- Compact equipment, low vibration
- Can be removed if ever needed (rare but useful for temporary works)
Cons
- Limited to lighter loads in most residential applications
- Cannot penetrate dense gravels or obstructions
- Less familiar to some loss adjusters than concrete methods
- Requires clear soil profile from investigation
How it compares
Every method we offer at a glance.
| Method | Time on site | Reaches | Disruption | Best for |
|---|---|---|---|---|
| Beam and base | 2 to 6 weeks | Up to 4m via deeper bases | High, large pits with significant excavation | Variable ground, bay windows, redistributing loads |
| Foam injection | 1 day for most jobs | Treats soil and slabs to 3m | Minimal, drilled ports only | Slab re-levelling, void fill, conservatory bases |
| Mass concrete | 2 to 6 weeks per elevation | Up to 3m hand-dug | High, open excavation and significant spoil | Shallow failures on traditional ground, insurance claims |
| Mini piled | 1 to 3 weeks on site | 10–15m, sometimes more | Medium, compact rigs and internal floor lifts | Deep bearing layers, made-up ground, restricted access |
| Resin injection | 1 day for most jobs | Treats soil to 3–4m via ports | Minimal, small ports and no spoil | Granular soils, intact foundations, voids and density loss |
| Screw pile | 2 to 5 days | 5–10m typical | Low, no excavation and no concrete cure | Lighter loads, time-critical jobs, conservatories |
Suitability
Copes well with soft alluvial ground, loose fill, and lighter residential loads up to about two storeys. Struggles with dense gravels, buried obstructions, and heavier loads that need either larger helices or a switch to mini piles. The diagnostic questions an engineer will ask first: do trial torque readings give the design capacity at a sensible depth, and is the soil profile clear enough to be confident about what each pile is biting into?
Common questions
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