Bognor Regis grew from a small fishing hamlet into a seaside resort after Sir Richard Hotham’s 18th-century vision, and that rapid expansion across the West Sussex coastal plain left a legacy of variable made ground and soft marine clays beneath much of the town. Designing a durable pavement here means dealing with that legacy head-on. The subgrade near the seafront often carries high moisture content, and seasonal groundwater fluctuations along the Aldwick and Felpham stretches push the need for precise CBR calibration. We approach each project by first mapping the soil profile, then layering the asphalt, base, and sub-base so the pavement flexes without rutting. For anyone handling a car park extension near the Butlin’s perimeter or a new access road off the A29, skipping that step leads to premature cracking. A CBR road assessment provides the stiffness baseline, and our team cross-checks it with in-situ permeability tests when drainage is the controlling factor.
A 15 mm adjustment in asphalt thickness, backed by proper CBR data, can cut tensile strain at the base layer by 30 percent in Bognor Regis’ variable coastal subgrades.
Site-specific factors
Bognor Regis sits on the boundary between the South Downs chalk and the low-lying coastal plain, so a single project can straddle two completely different subgrade behaviours within a hundred metres. The eastern half of the town, closer to Felpham, tends toward silty sands that drain reasonably well, while the central and western zones, particularly around the Aldingbourne Rife corridor, hold soft alluvial clays that lose strength rapidly when wet. That contrast creates a risk that is easy to miss during a dry summer site investigation. A pavement designed on August CBR values can be dangerously under-strength by February. We counter this by running soaked CBR tests as standard and by applying equilibrium suction models where the water table is within two metres of formation. The other risk is construction traffic. On weak ground, even a few passes of a loaded tipper truck before the capping layer is placed can remould the subgrade and halve its design stiffness. Sequencing the earthworks around the tide and the season matters here as much as the layer coefficients do.
Relevant standards
DMRB CD 225 – Design of new pavement foundations, BS EN 13285:2018 – Unbound mixtures. Specifications, BS 1377-4:1990 – Soils for civil engineering purposes. Compaction-related tests, BS 598-110:1998 – Sampling and examination of bituminous mixtures, MCHW Series 800 – Road pavements. Unbound, cement and other hydraulically bound mixtures
Common questions
What is the typical cost range for flexible pavement design on a Bognor Regis project?
For a medium-scale commercial or residential access road in the Bognor Regis area, the design package including site investigation, CBR profiling, and layer optimisation typically falls between £1,160 and £4,290, depending on the linear metres of pavement, the number of exploratory holes required, and whether FWD verification is included.
How does the coastal climate in Bognor Regis affect flexible pavement performance?
Salt spray accelerates binder oxidation in the surface course, so we specify polymer-modified bitumen for roads within about 500 metres of the seafront. High winter groundwater also means the subgrade rarely dries out fully; we use soaked CBR values as the design basis to avoid overestimating stiffness.
Do you follow DMRB or local West Sussex County Council standards?
We design to the DMRB CD 225 framework, which is the national standard adopted by West Sussex County Council for adopted highways. For private roads and car parks, we can apply the same methodology with adjusted design traffic, ensuring the pavement is solid but not unnecessarily thick.
How do you design pavements on the soft clay soils found in parts of Bognor Regis?
Where the subgrade CBR drops below 2 percent, we introduce a capping layer of stabilised material or thicker Type 1 sub-base to create a working platform and spread traffic loads. We also model the equilibrium moisture condition to predict long-term strength, rather than relying on a single snapshot CBR test.
