Most of the structural problems we encounter across Basildon start with a poor understanding of the soil's particle size distribution. It sounds simple, but getting grain size analysis wrong can lead to heave in clay, settlement under granular fill, or failed drainage layers. We run both dry sieving for coarse fractions and the hydrometer method for silts and clays, giving you a complete grading curve from 75 mm down to 2 microns. This dual approach is essential when working on the London Clay and Thanet Sand formations that underlie much of the borough. A proper grain size analysis report lets your engineer classify the material confidently and specify the right earthworks or foundation solution first time. For foundation design in cohesive soils near the Thames corridor, combining this test with atterberg limits gives a clear picture of plasticity and shrink-swell potential.
A 2-micron reading from the hydrometer test is often the deciding factor between a standard spread footing and a piled solution in Basildon's clay soils.
Methodology applied in Basildon
Risks and considerations in Basildon
Basildon's clay soils pose a particular challenge: they can look uniform in the hand but contain variable silt and sand seams that completely alter permeability and strength. We have seen several projects near the town centre where contractors assumed a well-graded granular fill based on visual inspection alone, only to discover excess fines during lab testing—leading to rejected material and costly re-excavation. A full grain size analysis removes that guesswork. The hydrometer portion is especially critical for assessing frost susceptibility and drainage characteristics in the upper 500 mm of formation. BS 5930 and Eurocode 7 both require particle size distribution as a fundamental descriptor for every ground investigation. Skipping the hydrometer step on fine-grained soils from the London Clay means you are missing half the story—and potentially exposing the structure to differential movement over time.
Our services
Our laboratory in the South East processes samples from across Basildon, from the industrial estates on the A127 corridor to residential developments in Laindon and Pitsea. Each service package includes a full grading curve, coefficient of uniformity and curvature, and a plain-English interpretation for your design team.
Combined Sieve and Hydrometer Package
The standard full-range analysis for cohesive and mixed soils. Covers coarse gravel down to clay-size particles. Delivered as a single PSF report with all BS 1377 worksheets attached.
Rapid Sand Grading for Concrete Aggregates
Dry sieve analysis only, focused on the 63 mm to 63 µm range. Ideal for checking compliance with BS 882 aggregate grading limits on tight construction schedules.
Hydrometer-Only Analysis for Fine Soils
Sedimentation analysis for clays and silts where the coarse fraction is negligible. Useful for assessing the drainage potential of pond liners, landfill caps, and attenuation features.
Common questions
How much sample material do you need for a combined sieve and hydrometer test?
For a typical Basildon clay or mixed soil, we need about 1 kg of material passing a 20 mm sieve. If the soil contains gravel or cobbles, we may need up to 25 kg to run the full coarse sieve stack. Our lab can advise after seeing a photo of the sample bag.
What does a grain size analysis cost for a small residential project?
A combined sieve and hydrometer test typically ranges from £70 to £160 depending on the number of size fractions and whether you need a rush turnaround. Single sieve-only runs for aggregates start at the lower end of that range.
How long does the hydrometer part of the test actually take?
The sedimentation readings run over a minimum 24-hour period, because the finest clay particles settle very slowly. After the final reading, we dry the suspension, weigh the residue, and calculate the full grading curve. Standard reporting is 3 to 5 working days from sample receipt.
Can I use a grading curve from a nearby site instead of testing my own plot?
We strongly advise against it. Basildon's superficial geology changes dramatically over short distances—Head deposits, brickearth, and terrace gravels can all appear within the same postcode. A grading curve from 100 metres away may not represent your formation, and your building control inspector will almost certainly require site-specific data.