Bath’s hillside setting means ground conditions can shift from stable limestone to soft alluvium within the length of a single terrace row. We see it regularly—a Victorian basement conversion on the slopes of Lansdown demands a completely different foundation approach than a new build down by the Avon floodplain. The cone penetration test provides a continuous vertical profile of the soil, logging tip resistance and sleeve friction in real time, which is especially useful where access is tight and traditional boreholes are impractical. Combining CPT data with lab-based grain size analysis helps our team distinguish between the weathered clays of the Charmouth Mudstone and the more competent Great Oolite limestone, ensuring bearing capacity calculations are based on actual stratigraphy, not just regional assumptions.
A single CPT sounding can replace multiple boreholes when the goal is continuous stratigraphy and undrained shear strength in soft clays.
Service characteristics in Bath
Live process video
Critical ground factors in Bath
A four-storey apartment block on Beechen Cliff started with a desk study that assumed uniform limestone bedrock. The CPT soundings told a different story. At 4.5 metres, the cone recorded a sudden drop in tip resistance, revealing a lens of saturated, loose silt that the original borehole logs had missed entirely. Without that continuous profile, the piled foundation design would have underestimated settlement by a factor of three, and the lower ground floor would have been exposed to differential movement within the first two winters. In Bath’s layered geology—where Jurassic clays and limestones alternate unpredictably—relying solely on widely spaced boreholes is a gamble. The cone penetration test captures the thin, weak seams that dictate how a structure will actually behave over time.
Our services
Our Bath-based CPT service covers the full investigation cycle, from initial site walkover to final factual report. Each sounding is calibrated daily and processed using software that outputs soil behaviour type charts in line with Robertson (1990) classification.
Piezocone (CPTu) Testing
Measures pore water pressure during penetration to assess consolidation characteristics and detect thin drainage layers within the Lias Clay.
Seismic CPT (SCPTu)
Adds a geophone array to record shear wave velocity, enabling direct calculation of small-strain stiffness for settlement and seismic site classification.
Dissipation Testing
Monitors pore pressure decay at a fixed depth, providing in-situ coefficient of consolidation data essential for predicting settlement rates in soft alluvium.
Factual and Interpretative Reports
Delivers processed CPT logs, soil behaviour type plots, and derived geotechnical parameters correlated with laboratory index testing results.
Quick answers
How much does a CPT test cost in Bath?
For sites around Bath, CPT testing typically ranges from £110 to £220 per sounding, depending on depth, rig access, and whether piezocone or seismic modules are required. Mobilisation is charged separately, and we provide a fixed quote after reviewing the site location and ground conditions.
Why choose CPT over traditional boreholes in Bath?
CPT gives a continuous, high-resolution record of soil resistance and pore pressure, making it far better at detecting thin weak layers that a standard borehole might miss. In Bath’s interbedded Jurassic strata, this detail is critical for safe foundation design, and the rig’s small footprint allows testing on narrow terraces where a drilling lorry cannot reach.
Can CPT penetrate the limestone bedrock common in Bath?
The reference range for this service in Bath is £110 - £220. The final price depends on the project scope and volume.
How long does a CPT investigation take on site?
A single CPT sounding to 15 metres typically takes 30 to 45 minutes. A full day on site in Bath can usually complete four to six soundings, including setup and calibration, depending on access constraints and the need for dissipation tests.