In short
Choose a weighbridge with four decisions that set with the concrete: surface or pit by soil and water table; a length that fits your longest whole vehicle; a capacity from the heaviest load that actually crosses, with margin; and its position on site. Also specify a data output at purchase.
Four decisions are made once, before the concrete is poured, and none of them can be changed afterwards without demolition. They deserve a week of thought, because they will govern how you work for ten years.
1 — Surface or pit?
A surface (above-ground) weighbridge sits on top of the ground and needs ramps at each end. Its civil works are simpler and cheaper, access to the cells and cabling for maintenance is easy, and drainage is natural because it is not in a pit.
A pit weighbridge sits flush with the ground. No ramps, so it saves considerable space and lets vehicles approach from any direction — decisive on a tight site or where trucks enter from two sides. But its civil works cost more, it needs effective drainage and ventilation, and maintenance underneath is harder.
Rule of thumb: if you have room for ramps, surface is cheaper and easier over a full life. If your water table is high, a pit deserves serious study — water under the deck is the fastest way to destroy load cells.
2 — Length
The basic rule: the whole vehicle must stand on the deck — every axle and the trailer. Anything off the deck means a wrong weight, and it is also the best-known route to manipulation, as covered in the article on stopping fraud.
Measure the longest vehicle you actually handle — not the average — and add a sensible margin for imperfect positioning. Then ask one question: is it likely you will handle longer trailers within five years? Extending the length later means, in practice, a new weighbridge.
Axle weighing is a separate matter: some sites need axle loads for regulatory reasons, which imposes its own requirements. Settle that before you buy, not after.
3 — Maximum capacity
Choose capacity from the heaviest load that actually crosses — including the occasionally overloaded truck — not from the heaviest legally permitted one. Then leave a safety margin above it.
Repeated overloading rarely breaks a weighbridge outright, but it pushes it out of adjustment and shortens cell life — so you pay in repeated calibrations and unstable readings rather than in an obvious failure.
4 — Where it sits on site
The most neglected decision, and the one you feel daily:
- A straight approach and exit. Vehicles should arrive straight and leave straight; turning on the deck damages surfaces and ruins positioning.
- Waiting space. Without it, trucks queue in the road — or sit on the deck while the ticket is prepared, blocking the next weighing.
- A view from the control room. The operator must see the whole deck, or a camera that covers it.
- Proximity to the gate. The closer weighing sits to the natural entry and exit path, the less manoeuvring — and the less room to work around the procedure.
- Drainage. Rain and wash water must run away from the bridge, not pool beneath it.
A fifth decision, usually made too late
How will the reading get from the scale into your books? This is normally deferred until after installation, an indicator without a data output gets bought, and manual copying becomes a fact of life for years.
Specifying a data output at purchase costs very little. Adding it later — or living without it — does not. The detail is in the article on connecting a weighbridge to a computer.
A short checklist before signing
- Did you measure the longest actual vehicle, not the average?
- Did you size capacity from the heaviest load that really crosses, with margin?
- Do you know the soil and water table before choosing surface or pit?
- Is there a straight approach, waiting space, and a view of the deck?
- Does the indicator have a data output?