Below-ground drainage run (110 mm) with inspection chambers: 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: 110 mm underground drainage pipe; Couplers, bends, junctions, rocker pipes; 450 mm plastic inspection chambers + covers; Pea gravel 10 mm
- Plant: Mini-digger hire
- Labour: Excavate, lay and backfill
- Waste: Surplus spoil (bulked)
The questions it asks
| Question | Unit / choices | Required? | Help |
|---|---|---|---|
| Drain run length | m | required | |
| Inspection chambers | nr | optional - default 1 (labelled assumed) | |
| Average invert depth | m | optional - default 0.9 (labelled assumed) | |
| Surface to reinstate | one of: soil, paving, tarmac, concrete | optional - default soil (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 |
|---|---|---|---|
| Pea gravel bed and surround per metre | 0.25 t/m | 150 mm bed + 150 mm surround in a 450 mm trench | assumed |
| Excavate, lay, surround, backfill per metre (machine) | 1.2 hr/m | trade practice | assumed |
| Set a plastic inspection chamber | 3 hr | trade practice | assumed |
A worked example
Answers used: Drain run length 4 m; Inspection chambers 1 nr; Average invert depth 0.9 m; Surface to reinstate soil. 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 | 110 mm underground drainage pipe | 4.2 m 2 x length - 3 m lengths | 4 m |
| material | Couplers, bends, junctions, rocker pipes | 5.33 nr 6 x nr - each | 4/3 + 4 |
| material | 450 mm plastic inspection chambers + covers | 1 nr 1 x nr - each | 1 |
| material | Pea gravel 10 mm | 1 t 2 x bag - bulk bags | 4 m x 0.25 t/m |
| plant | Mini-digger hire | 1 hire-day | hire-days = dig days |
| labour | Excavate, lay and backfill | 7.8 hr | 4 m x 1.2 h + 1 x 3 h |
| waste | Surplus spoil (bulked) | 0.84 m3 | 4 m x 0.45 m x 0.9 m x 40 % surplus x 1.3 |
Labour on this example: about 7.8 hours across the roles; at your rates it becomes money.
Site questions this work raises: Site access and neighbours, Waste, Utilities and welfare, Commercial and contract.
Specialists or hire it may need, drafted as enquiries from the job's facts: Grab lorry / muck-away, Plant hire.
Connections to a public sewer need the water company's consent; building control inspects before backfill.
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 below-ground drainage run (110 mm) with inspection chambers job now