The difference between designing a pavement in the Moseley clay and the sandy gravels of Sutton Coldfield is night and day. Birmingham's glacial till, with its variable boulder content, demands a site-specific approach rather than standard catalogue solutions. For a distributor road in Kingstanding, the subgrade CBR might be 2.5%; for a cul-de-sac in Edgbaston on Mercia Mudstone, it could hit 5% or more. That is why flexible pavement design in Birmingham always starts with a proper ground investigation — not assumptions. We combine CBR testing with soil classification to get the design right from day one.
Designing a pavement without knowing the subgrade CBR is like building a house without a foundation survey.
Scope of work in Birmingham
- traffic classification and ESA calculation per DMRB
- subgrade CBR determination from laboratory soaked CBR tests
- pavement layer thickness design using analytical or empirical methods
- drainage and frost protection check
Live process video
Critical ground factors in Birmingham
Birmingham sits on one of the largest accumulations of glacial till in the UK — up to 30 metres thick in parts of Harborne. This material can be highly variable in strength, with pockets of sand and gravel that cause differential settlement under the pavement. Without a thorough flexible pavement design that accounts for this variability, you risk cracking at the surface and premature rutting. Our laboratory team tests at least three CBR samples per formation layer to capture the spread. That is standard practice here, not exceptional.
Our services
We offer a complete suite of pavement-related services to support your project from ground investigation through to design review.
Site Investigation & CBR Testing
Full ground investigation including trial pits, window sampling, and laboratory soaked CBR tests on remoulded or undisturbed samples.
Traffic & ESA Analysis
Classification of traffic flows and calculation of equivalent standard axles (ESA) for the design life, following DMRB guidance.
Pavement Structural Design
Empirical and analytical design of flexible pavement layers — from sub-base to surface course — using recognised UK methods.
Drainage & Frost Assessment
Evaluation of pavement drainage requirements and frost susceptibility of subgrade and sub-base materials.
Q&A
How is flexible pavement design different for Birmingham's clay soils?
Birmingham's glacial till and Mercia Mudstone clays can have low soaked CBR values (often below 3%). That means thicker granular sub-base layers or a capping layer may be needed. Our designs always include a soaked CBR test to reflect worst-case conditions, not just natural moisture content.
What is the typical cost range for a flexible pavement design in Birmingham?
For a standard project — including site investigation, laboratory CBR tests, and full design report — the cost typically falls between £1,210 and £3,830. The final price depends on the number of test locations, traffic complexity, and whether drainage assessment is included.
Which British standards apply to flexible pavement design?
The main ones are Eurocode 7 (BS EN 1997-1:2004) for geotechnical design, DMRB CD 225 for pavement foundations, and BS 5930:2015 for site investigation. We also follow the CBR test method per BS EN 13286-47.
How many CBR tests are needed for a typical road project?
For a small residential road (up to 300 m), we recommend at least three CBR tests — one per 100 m of centreline. For larger distributor roads or industrial pavements, one test per 50 m is common. The number increases if the subgrade is variable, which it often is in Birmingham.