Freephone: 0800 074 0442
Cheshire: 01565 734 111
Bolton / Wigan: 01942 722 629
What’s under your feet decides your foundations — and the concrete you pour into them. A plain-English guide to the ground beneath Greater Manchester, Cheshire and Warrington, built from the published geology.
The North West sits on some of the most varied — and most awkward — ground in the country. Shallow coal workings under the Pennine fringe, deep peat in the mosses, soft alluvium along the river valleys, and the dissolving rock-salt beneath the Cheshire plain all change how a footing has to be dug and what concrete belongs in it. This Atlas pulls that scattered geology together, area by area, so you can see what to expect before you break ground.
We’ve built it from the authoritative published sources — the British Geological Survey’s Greater Manchester ground model, its geological memoirs, the Mining Remediation Authority’s coal data, and peer-reviewed research — and cited them throughout. We supply concrete across this whole region every day, so we see how the ground behaves in practice as well as on the map.
Much of Wigan, Bolton, Oldham, Tameside and eastern Stockport sits over the Lancashire Coalfield, where shallow abandoned workings can mean a Coal Authority mining search and, sometimes, grouting or piling through worked seams.
The river valleys and the great mosses — Chat Moss, Carrington — carry soft alluvium and deep peat that the BGS rates “generally unsuitable for most foundation types.” Here footings go deeper, or the load goes onto a raft or piles.
The Cheshire plain hides dissolving rock-salt that has swallowed whole streets; the old industrial river corridors hide made ground that can be chemically aggressive to concrete. Both change the mix you should order.
When George Stephenson drove the Liverpool & Manchester Railway across Chat Moss in 1830, the peat was so soft it swallowed everything tipped into it. His answer was to float the line on a raft of hurdles and brushwood rather than try to reach firm ground — the first great demonstration of the exact problem Greater Manchester’s soft ground still poses today. The materials have changed; the principle hasn’t. When the ground won’t carry the load, you spread it, or you go through it. Knowing which before you dig is what this Atlas is for.
The Atlas is grouped by the ground itself, not by council boundary, because geology doesn’t stop at a border. Find the zone your site sits in:
Triassic sandstone and mudstone, glacial till, and the dissolving rock-salt beneath Northwich, Winsford and Middlewich. Covers the Cheshire East and Knutsford-area towns.
Read the guide →Soft floodplain alluvium, buried channels, peat and made ground through Stockport, Trafford and south Warrington. Where a high water table shapes every footing.
Read the guide →Wigan, Bolton, Oldham, Bury, Rochdale, Salford and Tameside — shallow coal workings, mine entries, and when you need a Coal Mining Risk Assessment.
Read the guide →Chat Moss, Carrington and Risley — deep compressible peat and the piled and raft foundations that cope with it.
Read the guide →Glossop, New Mills, Whaley Bridge and Marple — gritstone, shallow variable rockhead, landslip ground and soft valley bottoms.
Read the guide →Every ground type points to a foundation response. This is the logic engineers work through — the Atlas zone guides tell you which situation you’re most likely in for a given area.
| Ground | What it means | Typical foundation response |
|---|---|---|
| Firm sandstone / stiff till at shallow depth | Good bearing near the surface | Strip or trench-fill footings usually adequate |
| Variable or water-bearing glacial till | Bearing depends on sand/silt lenses & water | Wider strip, local dewatering, sometimes a raft |
| Soft alluvium on a floodplain | Low bearing, settles under load | Deeper trench-fill, raft, or piles |
| Peat | Very soft, highly compressible | Remove, or pile through to firm ground |
| Shallow coal workings / salt-affected ground | Risk of collapse or subsidence | Mining/brine search, grouting, piling or jackable design |
Ground chemistry matters as much as ground strength. Where old industrial fill, gypsum-bearing Mercia Mudstone or brine-affected ground is present, buried concrete can be attacked by sulfates. Under BS 8500 and BRE Special Digest 1, a ground investigation measures the sulfate and pH, assigns a Design Sulfate Class and an ACEC class, and that sets the concrete’s DC class — which may call for sulfate-resisting cement. On clean, tested natural ground an ordinary designated foundation mix is often fine; on brownfield or aggressive ground you’ll need a higher DC-class foundation concrete.
You don’t have to work this out alone. Tell us the class your ground investigation gives you and we’ll supply the matching mix — including sulfate-resisting options — mixed fresh on site.
Geology and old mine workings aren’t the only things under a plot that change what you build. In some areas the ground gives off radon, a natural radioactive gas the building regs ask the floor slab to hold back; along the rivers, flood risk drives raised floor levels and flood-resilient slabs. Both change how the concrete floor goes in.
Where radon affects the North West (mainly the Peak/Pennine fringe), what the regs (BR 211) require, and how the radon barrier and sump change the slab.
Read the guide →The EA flood zones along the Mersey, Irwell, Goyt, Bollin, Weaver and Dane — and how raised floor levels and flood-resilient concrete change the slab you pour.
Read the guide →• See our ready-mix for foundations & footings
• Work out how much you need with the concrete calculators
• Awkward access on a soft or tight site? Concrete pumping and volumetric mixing earn their keep here
• Find your town in the areas we cover
Because the ground sets two things: how the foundation is built (strip, raft or piled) and what concrete can survive in it. Soft or peaty ground changes the foundation; chemically aggressive or brownfield ground changes the concrete mix. Getting both right from the start avoids cracking, settlement and costly remedial work.
No — and nothing regional can. It tells you what the ground in your area is likely to be and what to test for. Your actual foundation design and concrete class come from a site-specific ground investigation. Treat the Atlas as the questions to ask your engineer, not the answers.
It can. Made ground from former industry may carry elevated sulfates and variable pH, which raises the concrete’s required DC class under BS 8500 / BRE Special Digest 1 and may call for sulfate-resisting cement. A chemical soil test decides it — send us the class and we’ll match the mix.
We’re a concrete supplier, not a structural engineer, so the foundation design and soil testing are your engineer’s job. What we bring is local knowledge of how this ground behaves and the right mix to the class your investigation specifies — supplied fresh, barrowed or pumped wherever it needs to go.
Sources: British Geological Survey, Geological ground model for planning and development for Greater Manchester (Open Report OR/20/033); BGS geological memoirs and the Mercia Mudstone Group engineering-geology guidance; A.H. Cooper (2020), Geological hazards from salt mining, brine extraction and natural salt dissolution in the UK, Geological Society Engineering Geology Special Publication 29; Mining Remediation Authority (formerly the Coal Authority) coal-mining data (Open Government Licence v3); BS 8500-1 and BRE Special Digest 1. General guidance only — not a substitute for a site-specific ground investigation.
Foundations, footings, rafts and slabs across Greater Manchester, Cheshire & Warrington — supplied to the spec your job needs.