A spreadsheet can add every row correctly and still produce the wrong estimate. The problem may sit in what was measured, what was left out or what the rates assume. None of those errors necessarily causes a formula warning.
Our estimate-review exercise uses eight rows. Two repeat the same excavation, one concrete quantity has the wrong unit, a supply-and-install item has no material, a manual excavation output is implausible, a waste factor is misapplied and one extension is wrong. One row is sound.
The purpose is not to find as many faults as possible. It is to distinguish a supported concern from a correct item and explain the correction clearly enough for another person to act on it.
| Signal | Question |
|---|---|
| Repeated excavation quantity | Distinct work or the same scope twice? |
| m² quantity with a rate per m³ | Where is the thickness conversion? |
| Supply and install with no material | Is supply priced elsewhere? |
| Unexpectedly high manual output | What method and crew support it? |
| A 3% factor gives only 3% of the cost | Was 0.03 used instead of 1.03? |
| 100 × £32 shown as £320 | Has the extension lost a factor of ten? |
The practice estimate contains these six issue types. Two lines describe the same duplicated excavation scope.
Begin with the scope
The excavation appears twice at 1,200 m³. Both extensions can be correct, but that does not make both quantities legitimate. Check drawing references, location and description before deleting anything. Repeated descriptions can also represent separate work in different areas.
In this exercise the duplication is explicit, so both rows should be classified as a duplicate line. Retain one valid quantity record and remove the repeated cost. Do not solve the problem by halving both quantities: that disguises the scope rather than clarifying it.
Treat units as part of the description
A concrete item measured in square metres cannot use a rate per cubic metre without a thickness conversion. It may be a labelling error, or the quantity itself may be wrong. Establish which one before accepting a revised total.
Similarly, “supply and install” prompts a check for both supply and installation cost. A zero material component is not automatically an error if material is priced elsewhere. In the exercise it is missing. In a real estimate, follow the reference before adding an allowance and creating duplication.
Ask whether the output is plausible
The manual excavation row states 800 m³ per hour. Its rate can be calculated, but the scenario provides no method or crew that supports such production. Challenge the assumption rather than polishing the resulting decimals.
- Reconcile scope
- Confirm quantities and units
- Challenge resource assumptions
- Check arithmetic
- Record actions
Correct formulas cannot prove that the scope is complete.
Productivity review is especially useful when a rate seems surprisingly attractive. Confirm the volume state, time basis, equipment, access and working conditions. A rate copied from another project may be accurate for that project and unsuitable for this one.
Separate an allowance from the whole quantity
A 3% purchasing addition uses a factor of 1.03. A factor of 0.03 prices only the additional portion. This is a conceptual mistake that a spreadsheet happily carries through later calculations.
The extension error is direct: 100 m² at £32 per m² is £3,200, not £320. Independent recalculation catches it. A subtotal check may reveal that a package is unexpectedly low, but it will not explain why until the underlying row is inspected.
Leave a useful review record
Record the item, concern, evidence and action needed. “Rate seems low” is a starting observation. “Confirm whether crew output includes access delays and identify the source of the production assumption” gives someone a task they can close.
The sound blinding row should remain classified as no issue. Good review is not a contest to mark every line. It is a controlled examination of whether the estimate represents the stated work, with a clear trail from question to resolution.