The as-built nobody can draw
Your drainage gang has laid the foul and surface water on a housing phase: pipe runs, manholes, inspection chambers, plot connections. The pipe layer or engineer took levels as they went, in a notebook and on a print in the van. Now the housebuilder wants as-built drawings, and the water company will want them for adoption. The notebook has most of the levels. A few runs were changed on site to avoid a service. The print with the changes marked on it got wet.
Someone ends up re-surveying manholes and lifting covers to measure depths, weeks after the work was done.
Why as-laid records go missing
Levels are recorded because the gang needs them to lay the pipe to fall. Recording them for someone else, in a form a drawing can use, is a separate job with no immediate reward. Changes on site are made for good reasons and remembered, not written. The paper record lives in a van until it is needed.
- Invert and cover levels are written in notebooks.
- Changes to runs and manhole positions are marked on paper prints.
- Pipe material, size and length are not recorded per run.
- Plot connection positions are not measured and recorded.
- The as-built is produced weeks later from whatever survives.
What missing records cost
Re-surveying manholes and runs to produce drawings you should already have. Delays to the housebuilder's handover and to adoption, which can hold up money. Disputes about whether the drainage was laid as designed, with no record to show what was done and why it changed. And a poor impression with the engineer and the water company, who see a lot of late as-built packs.
As-laid recording we build
- The design drainage layout is loaded, with each run and manhole referenced as on the drawing.
- As each run is laid, the pipe layer or engineer selects it on a phone or tablet and records invert levels at each end, pipe material, diameter and length, bedding type and any change from design, with a reason.
- Each manhole or chamber gets its cover and invert levels, depth, size, connections and a photo inside and out.
- Plot connections and junctions are recorded with position and level.
- Readings are compared with design levels and gradients as they are entered, and differences beyond your tolerance are flagged straight away.
- Where you use a GPS rover or total station, readings can be imported instead of typed.
- The as-laid data is exported in the format your engineer or surveyor uses to produce the as-built drawing, with a schedule of manholes and runs.
| Recorded item | Captured | Used for |
|---|---|---|
| Run invert levels | Each end, as laid | Gradient check and as-built |
| Pipe details | Material, size, length | As-built schedule |
| Manhole details | Cover, inverts, depth, photos | Manhole schedule |
| Changes from design | With reason and photo | Explaining the as-built |
| Plot connections | Position and level | Housebuilder and adoption |
Design tolerances and what counts as acceptable are set by the engineer and the adopting body. We record against them; we do not set them.
As-builts from the day's work
The as-built record exists as the drainage goes in, not weeks later. Changes on site are explained at the time. Your engineer or surveyor produces the drawing from data rather than from a damp notebook. The housebuilder and the water company get their information sooner. And if a level is out, it is flagged while the trench is still open.
Are your drainage records like this?
- Levels live in a notebook in the van.
- Changes on site are marked on paper prints.
- You have re-surveyed manholes to produce as-builts.
- As-built drawings hold up handover or adoption.
- Out-of-tolerance levels are found after backfilling.