Concrete for Foundations and Footings
Strip footings, trench fill, reinforced rafts, awkward ground — the right foundation mix, batched fresh at the trench and metered as it pours. From 0.5m³, no part-load penalty.
Which Concrete for Foundations?
For unreinforced strip or trench-fill foundations in normal ground, the answer is straightforward: C8/10 — what builders call GEN1. It's a general-purpose foundation strength, and we batch an equivalent designed mix to the strength and durability requirements of BS 8500 / BS EN 206. Don't pay for a stronger grade than the job needs; for a plain footing in decent ground, this is the mix.
Strip foundations vs trench fill
The strength is the same for both — what changes is the consistence. Strip foundations take a standard S3 mix. Trench fill is ordered at S4: a high-slump, almost self-compacting consistence that flows along the trench, finds its own level and fills against the excavated faces without a fight. On a trench-fill pour the concrete does most of the work — which is exactly the point.
One thing we won't do is "loosen it up" with a hose on site. Unauthorised added water invalidates the performance of the mix and weakens it. Because we batch on site, we set the workability properly at the point of mixing instead — if you want it to flow, it's designed to flow.
Reinforced foundations
Anything with embedded metal counts as reinforced — and GEN-type mixes are for unreinforced work only. Reinforced foundations step up to C25/30 at S3 consistence — what the trade calls 30-newton concrete. See our C25 concrete page for the detail, or concrete grades explained for the full family tree.
Sulfate and brownfield ground
Some ground attacks ordinary concrete. Sulphates can be a factor on former industrial land — and parts of Birmingham and the Black Country sit on made ground from their industrial past. This is never judged by eye: it's triggered by a ground investigation on sulfate clays, pyrite or brownfield made ground.
The report's DC class maps directly to an FND-equivalent designed mix (DC-2 → FND2, and so on). All FND-class mixes are C25/30 strength — the difference is durability against the ground, not load-bearing grunt. Send us the report page and we'll spec the mix from it.
How Much Concrete Do Foundations Need?
Total trench length × width × depth, all in metres. Worked example: a 12m run of 600mm-wide trench dug to 1m deep is 12 × 0.6 × 1.0 = 7.2m³ — with 5–10% contingency, order 7.75–8m³.
Two pieces of hard-won advice. First, measure the trench as dug, not as drawn — trenches rarely come out of the ground as neat as they went onto paper. Second, add that 5–10% anyway: soft spots, bulges and over-dig all eat concrete.
With a drum supplier, getting this wrong costs money in both directions. With us it's relaxed: we carry more material than the estimate, batch at the trench, and the meter records what's poured. Run your numbers through our concrete calculator — it does the trench maths, the contingency and the mix suggestion in one go.
Getting It Into the Trench
Foundation pours are quick when the access is planned. Direct discharge runs at roughly 1m³ a minute, so even a full extension footing goes in fast — and an S4 trench-fill mix flows along the trench rather than needing to be dragged.
The truck needs about 3m of clear width and ground that takes a heavy lorry — tell us about soft verges, covers and drives and we plan around them. Our volumetric trucks carry extension chutes reaching around 5m, which covers a lot of set-back trenches that would beat a standard drum mixer's 2.4–2.75m reach.
When the chute can't get there: wheelbarrowing works for small volumes — reckon on about 20 barrow loads per m³, at 100kg-plus a barrow, with at least one barrow and one able adult per cubic metre to keep pace. Beyond a couple of cubic metres of barrowing, a pump wins: it moves around 1m³ a minute, and a line pump reaches hundreds of metres horizontally. We arrange concrete pump hire and the concrete in one phone call — the decision is about access and volume, so describe the site and we'll tell you straight whether you need one.
Building Control and the Pour
Foundations get inspected before they're poured — building control (or your approved inspector) wants to see the open excavation and sign it off first. That's a general point of process, not legal advice: your builder or inspector confirms the requirements for your job.
What it means for ordering is simple: book the concrete for after the sign-off, not before. Same-day slots are often available, so a trench passed in the morning can usually be poured the same day rather than standing open collecting rainwater.
And if the inspector asks for deeper once the ground is open — it happens — volumetric supply takes the drama out of it. We batch what the final dig needs and you pay the metered volume. Every load comes with a batch ticket recording the mix and strength class, consistence, batch time and metered volume, so what went into your foundations is documented.
Foundation Concrete Prices
| Foundation mix | Use | Guide price per m³ |
|---|---|---|
| C8/10 (GEN1-equivalent), S3 or S4 | Unreinforced strip & trench-fill foundations, normal ground | from £99 |
| C25 (C25/30), S3 | Reinforced foundations | from £110 |
| FND-equivalent designed mix (C25/30 strength) | Sulfate ground, to your soil report's DC class | quoted per spec |
All prices per m³, +VAT (add 20%), guide prices — confirmed when you book. So the 7.2m³ trench-fill example above is roughly £713–£792 +VAT of concrete, metered as it pours. Full pricing, including pumping and small loads, is in our ready mix concrete prices guide.
Foundation Concrete FAQs
What grade of concrete is used for house foundations?
For unreinforced strip or trench-fill foundations in normal ground, a C8/10 mix — what builders call GEN1 — is the standard. If the foundation contains any embedded steel it counts as reinforced and steps up to C25/30. If a soil report flags aggressive ground, a sulfate-resisting designed mix to the report's DC class is needed instead.
What is the difference between strip foundations and trench fill?
Strip foundations use a relatively thin band of concrete at the bottom of the trench with masonry built up off it; trench fill fills most of the trench with concrete instead. The strength is the same — C8/10 in normal ground — but trench fill is ordered at S4 consistence: a high-slump mix that flows into place and is almost self-compacting.
Do I need sulfate-resisting concrete for foundations in Birmingham?
Only a ground investigation can tell you. Sulphates can be a factor on former industrial land in parts of Birmingham and the Black Country, where they can attack ordinary concrete. If your ground report specifies a DC class, we batch an FND-equivalent designed mix to match it — it's never judged by eye.
My drawings say GEN1 — can you supply it?
What builders call GEN1 is a C8/10-strength general-purpose mix — we batch an equivalent designed mix to the strength and durability requirements of BS 8500 / BS EN 206. Designated names like GEN1 may only be used by producers holding third-party certification. If your spec strictly requires certified designated concrete — NHBC specs do, for example — tell us and we'll say so plainly and advise.
How much concrete do foundations need?
Total trench length × width × depth, all in metres. A 12m run of 600mm-wide trench at 1m deep is 12 × 0.6 × 1.0 = 7.2m³ — order 7.75–8m³ with contingency. Measure as dug, not as drawn, and check your numbers with our concrete calculator.
What if building control changes the depth on the day?
It happens — the inspector sees the ground open and asks for deeper. With volumetric supply it isn't a crisis: the truck carries more material than the estimate, batches on site, and you pay for the metered volume that's actually poured. No anxious re-ordering, no part-load fees for a top-up.
Footings Ready to Pour?
Tell us the trench dimensions and the ground, and we'll confirm the mix, the volume and the price in one call. Batched at your trench, metered as it pours.