SPT Standard Penetration Test in Edinburgh

Edinburgh sits on a mix of glacial till, raised beach deposits, and soft clays. In our experience, the N-values from the SPT Standard Penetration Test tell you exactly how that ground will behave under load. We run the test to BS EN 1997-2, using a standard 63.5 kg hammer dropped 760 mm. The sampler is driven 450 mm, and we record blows for each 150 mm increment. That first 150 mm is a seating drive, and the sum of the next two gives the N-value. Before you pour concrete, you need those numbers. For shallow foundations we often pair the SPT with a placa de carga to verify modulus directly at formation level.

The SPT N-value from Edinburgh's glacial till is your most direct indicator of bearing capacity and liquefaction resistance.

Scope of work in Edinburgh

A typical project in Edinburgh might be a five-storey residential block in the New Town, where the upper soils are made ground over dense till. The SPT Standard Penetration Test is our go-to tool there. We follow BS EN ISO 22476-3 for the split-barrel sampler and record energy efficiency with a calibrated hammer. The rig reaches refusal at around 50 blows per 300 mm in the till, and we log the soil type from the recovered sample. For deeper investigations, like the ones for foundations in the old volcanic necks below the Castle Rock, we complement the SPT with ensayo cpt to get continuous profiles in the softer layers. The test is straightforward, quick, and gives you a direct measure of relative density or consistency.

SPT Standard Penetration Test in Edinburgh

Parameter	Typical value
Hammer weight	63.5 kg
Drop height	760 mm
Sampler type	Split-barrel, 50.8 mm OD, 35 mm ID
Seating drive	150 mm
Test drive	300 mm (2 increments of 150 mm)
N-value	Sum of blows in last 300 mm
Energy ratio target	60% (calibrated hammer)
Refusal criterion	50 blows for any 150 mm increment

Typical technical challenges in Edinburgh

Edinburgh lies about 55 degrees north, with a population over 500,000. The city is not in a high seismic zone, but the British Geological Survey records small events every few years. The real risk here is variable ground: made ground over soft clays, peat in the Meadows area, and boulders in the till. An SPT Standard Penetration Test catches that variability. A single low N-value in a borehole can mean a change in foundation design, from pads to piles. Missing a weak zone in the soft clay under Leith could cost far more than the test itself.

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Applicable standards: BS EN 1997-2:2007 (Eurocode 7 – Ground investigation and testing), BS 5930:2015 (Code of practice for ground investigations), BS EN ISO 22476-3 (Standard Test Method for SPT), AASHTO T-206 (Standard Method of Test for SPT)

Our services

We offer a full range of SPT-based services tailored to Edinburgh's geology. Each includes field logging, sample recovery, and a certified report.

Borehole SPT with Continuous Sampling

We drill and perform SPT at 1.5 m intervals in each borehole. Samples are recovered for classification and laboratory testing. Ideal for residential and commercial sites.

SPT in Made Ground and Fill

Targeted SPT in old landfill, railway embankments, or historic fill areas. We assess compaction and identify potential voids or soft spots before foundation design.

SPT for Pile Design Parameters

N-values are correlated with shaft friction and end-bearing resistance for driven and bored piles. We provide site-specific correlations based on Edinburgh's till and clay formations.

SPT with Energy Measurement

We use an instrumented hammer to measure actual energy transfer. This gives corrected N60 values, essential for liquefaction assessment and high-spec designs under Eurocode 7.

FAQ

How much does an SPT cost in Edinburgh?

A standard SPT test in a single borehole, including sampling and a basic field report, ranges between £440 and £550. Costs vary with depth, number of tests, and site access conditions. We provide a fixed quote after reviewing the project scope.

What N-value should I expect in Edinburgh's glacial till?

In the dense glacial till found across central Edinburgh and the suburbs, N-values typically range from 30 to 50 blows per 300 mm. In the softer clays under Leith and the Water of Leith floodplain, expect N-values between 5 and 15. Made ground can vary from 2 to over 40 depending on compaction and composition.

Can I use SPT results for liquefaction assessment in Edinburgh?

Yes, but the risk is low. You need corrected N60 values and energy measurements to apply the Youd-Idriss (2001) method. In Edinburgh, only loose saturated sands in the old river terraces or reclaimed dock areas would trigger a liquefaction check. We include the necessary corrections in our report.