Standard Penetration Test (SPT) in Ipswich: Reliable Subsurface Data for Your Project

For a single-detached house site in Ipswich, a programme of two SPT boreholes to 10 metres depth typically falls between £420 and £690 per borehole, depending on access conditions, casing requirements, and whether you need factual or interpretative reporting. Sites in the alluvial zones near the Gipping — where we often encounter soft ground requiring full casing through the upper 4–5 metres — tend toward the upper end of that range. We supply a fixed-price proposal after reviewing the site location and any existing ground information you can share.

For a two-storey extension on the Anglian till that covers much of north and east Ipswich, we generally recommend boreholes to 8–10 metres. If you are on the river terrace gravels or made ground near the town centre, we may suggest going to 12–15 metres because the variable thickness of the alluvium can hide compressible layers at depth. The key is to reach a stratum where N-values consistently exceed 15 and the soil description confirms a competent bearing material — usually the till or the underlying Crag Sand.

Yes, we apply both energy and overburden corrections in line with BS EN 1997-2 and the recommendations in BS 5930. Each of our SPT hammers is calibrated annually using an instrumented rod to measure the actual energy delivered; the resulting energy ratio is reported on every borehole log. Overburden correction follows the Liao and Whitman (1986) method as endorsed by the UK specification for ground investigation. You receive both raw N-values and corrected N60 values in the final report.

Fieldwork for a typical two-borehole programme takes one to two days on site, assuming reasonable access and no buried obstructions. Laboratory classification testing on the recovered samples is normally completed within five working days. The factual report — including borehole logs, SPT N-value plots, and laboratory results — is usually delivered within ten working days of the rig leaving site. If you need an interpretative report with foundation recommendations, add another five working days.