1. Why the same element yields different quantities
Three reasons, all of them legitimate, and the third has the greatest effect. It concerns the measurement rules.
| Reason | Question |
|---|---|
| Openings | whether window and door openings are deducted from the wall area, and above what size |
| Overlaps | whether the meeting of wall and ceiling is counted to one or the other |
| Extent of the work | whether preparation, cleaning and removal belong within the line |
The third is also the least often written down. None of them is wrong: the assumptions are simply different, and the problem arises when the assumptions differ and nobody knows it.
2. Four typical disagreements
They recur from project to project, and the fourth is particularly expensive in reconstruction. Quantities are least clear there.
| Disagreement | Content |
|---|---|
| Finishes at openings | whether the internal faces of openings belong within the wall area |
| The boundary of foundation and ground | where excavation ends and foundation work begins |
| Penetrations for building services | whose work covers forming and making good the opening |
| Temporary works | whether scaffolding, covering and temporary heating are a separate line or inside the prices |
In reconstruction, temporary works may be a substantial part of the cost. All four are resolved by one sentence in the base document, where that sentence exists.
3. What to agree
Four things fit on a single page. Whether openings are deducted and above what area. How overlaps and boundary zones are treated. What belongs within the line besides the main work, that is preparation, clearing and removal. And where the boundaries of the positions lie, that is which work belongs in which line.
The fourth is bound up with the classification, as covered by the article on a common classification: where the classification is common and the names are not changed, most boundary questions are already resolved. Classification and measurement rule go together.
4. Why it is rarely done
Three reasons, and the first is the most deceptive. Experienced parties assume the rules are known in any case. Writing the rules down seems superfluous until a dispute arises. And the dispute arises only during construction, when agreement is already difficult.
Two experienced parties may be experienced in different practice, and with international parties the difference is more likely still, since measurement conventions differ from country to country. The professional recommendation follows directly: write the rules out precisely when it seems everyone knows them anyway.
5. What happens when there is no rule
Three consequences, and the third is the most unfair. Tenders are not comparable even though the structure is the same. A dispute over quantity arises during construction, which is always more expensive than a prior agreement. And the resolution of the dispute depends on bargaining power, not on a rule.
The third can be avoided entirely, and the reason fits in one sentence: a rule agreed beforehand protects both parties. A rule agreed afterwards protects the stronger one.
Summary and four practical rules
A quantity depends on the measurement rule, and three legitimate reasons give the same element a different quantity: the treatment of openings, overlaps, and the extent of the work. Four typical disagreements recur from project to project, and temporary works are a particularly expensive case in reconstruction, yet all four are resolved by one sentence in the base document. Writing the rules down seems superfluous until a dispute arises, and two experienced parties may be experienced in different practice.
Four rules: write the measurement rules out even when they seem obvious. State what belongs within the line besides the main work. Treat temporary works separately, especially in reconstruction. Agree the rules before inviting tenders, not during a dispute.
This article offers professional orientation as at the date of verification. It replaces neither a quotation nor the assessment of a competent specialist.