SPT (Standard Penetration Test) in Ashford – BS 5930 Compliant

For a single borehole to 10 metres depth with SPT at standard intervals, budget between £430 and £680. The final cost depends on access, traffic management if working on a public road, and the number of samples requiring laboratory testing. A campaign of three to four boreholes typically reduces the per-metre rate.

BS 5930 does not prescribe a fixed number; it depends on the site’s geotechnical category and the uniformity of the ground. For a Category 2 structure on Ashford’s variable Weald Clay and Hythe Beds, we usually recommend a minimum of three boreholes spaced to capture lateral changes.

The raw SPT N-value is the blow count recorded in the field. N60 corrects that raw number to 60% of the theoretical hammer energy, accounting for rod length, borehole diameter, and sampler type. Our automatic trip hammers are calibrated for energy ratio, and we report both raw N and N60 on the borehole log so the structural engineer can select appropriate design parameters.

Yes, but it depends on headroom and access width. We have compact tracked rigs that fit through a standard door opening when required. For very restricted spaces, we may recommend a CPT instead, which uses a smaller rig footprint and still provides continuous penetration resistance.

Fieldwork for a typical three-borehole campaign in Ashford takes one to two days. Laboratory testing adds five working days. The final factual report, including borehole logs, N-values, and laboratory results, is delivered within ten working days of completing fieldwork.