Ground-bearing concrete slab (hardcore, DPM, insulation, concrete): 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 (GEN3 / RC to spec); MOT type 1 hardcore; Sand blinding 50 mm; 1200-gauge DPM + tape; PIR floor insulation 100 mm; A142 mesh reinforcement
- Plant: Plate compactor hire
- Labour: Dig out, hardcore, blind, DPM, insulation; Place, tamp and float
- Waste: Reduce-level spoil (bulked)
The questions it asks
| Question | Unit / choices | Required? | Help |
|---|---|---|---|
| Slab area | m2 | required | |
| Concrete thickness | mm | optional - default 150 (labelled assumed) | |
| Hardcore thickness | mm | optional - default 150 (labelled assumed) | |
| Insulation under the slab? | yes / no | optional - default yes (labelled assumed) | |
| Reduce-level dig depth | mm | optional - default 350 (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 |
|---|---|---|---|
| MOT type 1 compacted | 2.1 t/m3 | typical | assumed |
| Dig out, hardcore, blind, DPM per m2 | 0.4 hr/m2 | trade practice | assumed |
| Place, tamp and float per m2 | 0.25 hr/m2 | trade practice | assumed |
A worked example
Answers used: Slab area 20 m2; Concrete thickness 150 mm; Hardcore thickness 150 mm; Insulation under the slab? yes; Reduce-level dig depth 350 mm. 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 (GEN3 / RC to spec) | 3.15 m3 13 x m3 - 0.25 m3 steps | 20 m2 x 150 mm |
| material | MOT type 1 hardcore | 6.62 t 8 x bag - bulk bags ~850 kg (or loose by the tonne) | 20 m2 x 150 mm x 2.1 t/m3 |
| material | Sand blinding 50 mm | 1.6 t 2 x bag - bulk bags | 20 m2 x 50 mm |
| material | 1200-gauge DPM + tape | 23 m2 1 x roll - 4 x 25 m rolls | 20 m2 +15 % laps |
| material | PIR floor insulation 100 mm | 21 m2 8 x sheet - 2.88 m2 boards | 20 m2 |
| material | A142 mesh reinforcement | 22 m2 2 x sheet - 4.8 x 2.4 m sheets | 20 m2 +10 % laps |
| plant | Plate compactor hire | 1 hire-day | 1 day per ~40 m2 |
| labour | Dig out, hardcore, blind, DPM, insulation | 8 hr | 20 m2 x 0.4 h/m2 |
| labour | Place, tamp and float | 5 hr | 20 m2 x 0.25 h/m2 |
| waste | Reduce-level spoil (bulked) | 9.1 m3 | 20 m2 x 350 mm x 1.3 |
Labour on this example: about 13 hours across the roles; at your rates it becomes money.
Site questions this work raises: Site access and neighbours, Waste, Parking and traffic, Utilities and welfare.
Specialists or hire it may need, drafted as enquiries from the job's facts: Grab lorry / muck-away, Ready-mix concrete, Materials (merchant) delivery.
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.
Start a ground-bearing concrete slab (hardcore, dpm, insulation, concrete) job now