Excavate and concrete strip foundations: calculator for UK builders
Answer the measurements this calculation needs and JobBosh works out the materials with wastage and pack rounding, the labour hours by role, the plant, the waste and the site needs - then prices them from your own figures, a supplier's quotation or a dated price you record. Free, no account needed to start.
What it works out
- Material: Ready-mix concrete GEN1/GEN3 (foundation grade to spec)
- Plant: Mini-digger hire (1.5 t) incl. delivery/collection
- Labour: Excavate trenches (machine + banksman); Place and level concrete
- Waste: Excavated spoil to remove (grab lorry)
The questions it asks
| Question | Unit / choices | Required? | Help |
|---|---|---|---|
| Trench length | m | required | |
| Trench width | m | optional - default 0.6 (labelled assumed) | |
| Trench depth | m | optional - default 1.0 (labelled assumed) | To the engineer's / building control depth; 1.0 m is common, clay and trees go deeper. |
| Concrete depth | m | optional - default 0.6 (labelled assumed) | |
| Spoil disposal | one of: grab lorry, skips, keep on site | optional - default grab_lorry (labelled assumed) | |
| Can a mini-digger reach the trench? | yes / no | optional - default yes (labelled assumed) |
The norms behind it, with their sources
Coverage, productivity and wastage defaults you can edit; each carries where it comes from and is shown as assumed until your own benchmark replaces it.
| Norm | Value | Source | Tier |
|---|---|---|---|
| Excavated soil bulks by ~30 % | 1.3 x | trade practice (clay 30-40 %) | assumed |
| Mini-digger excavation per m3 incl. driver | 0.5 hr/m3 | trade practice | assumed |
| Hand dig per m3 | 3 hr/m3 | trade practice | assumed |
| Place and level concrete per m3 (ready-mix, barrowed) | 0.8 hr/m3 | trade practice | assumed |
A worked example
Answers used: Trench length 4 m; Trench width 0.6 m; Trench depth 1.0 m; Concrete depth 0.6 m; Spoil disposal grab lorry; Can a mini-digger reach the trench? yes. These are the recipe's own quantities for those answers - the prices are yours, the supplier's or a quotation's, never a figure typed on a web page.
| Kind | Line | Quantity | How it is worked out |
|---|---|---|---|
| material | Ready-mix concrete GEN1/GEN3 (foundation grade to spec) | 1.51 m3 7 x m3 - delivered in 0.25 m3 steps | 4 x 0.6 x 0.6 m +5 % |
| plant | Mini-digger hire (1.5 t) incl. delivery/collection | 1 hire-day | 2.40 m3 x 0.5 h/m3 / 8 h days |
| labour | Excavate trenches (machine + banksman) | 2.4 hr | 2.40 m3 x 0.5 h/m3 x 2 people |
| labour | Place and level concrete | 1.15 hr | 1.44 m3 x 0.8 h/m3 |
| waste | Excavated spoil to remove (grab lorry) | 3.12 m3 | 2.40 m3 x 1.3 bulking |
Labour on this example: about 3.55 hours across the roles; at your rates it becomes money.
Site questions this work raises: Site access and neighbours, Parking and traffic, Utilities and welfare, Waste, Commercial and contract.
Specialists or hire it may need, drafted as enquiries from the job's facts: Grab lorry / muck-away, Ready-mix concrete.
Building control inspects the trench before the pour: programme the inspection.
Deeper trenches (over 1.2 m) need support: the engineer's call.
Then what
Price the lines from your crew rates and your material prices (each with its source and date), answer the site questions (parking, skip, welfare, power, water, protection), let JobBosh draft the supplier enquiries you approve, and issue a branded quotation your customer accepts on a secure link. Guest work is kept for 14 days; a free account keeps it for good.