The three conditions
They are cumulative.
A common basis. Every contractor received the same package, with the same items, the same quantities and the same requirements.
An identical scope. The bids cover the same works, with no unflagged exclusion or addition.
The same information. Queries and answers were circulated to all, as the article on queries and corrections explains.
If a single one of these conditions is missing, the comparison no longer measures price but difference of scope.
| Condition | What it requires | Consequence if absent |
|---|---|---|
| Same scope | An identical schedule for all | Distorted comparison |
| Same assumptions | Common quantities and units | Unexplainable variances |
| Same conditions | Identical time limits and clauses | Prices not comparable |
Why it is built beforehand
Three reasons, explaining this guide's insistence on the upstream phase. Comparability is built before tendering, not after.
The common schedule is what aligns the items. Without it, each contractor structures its quotation its own way, and the lines do not correspond.
The common description is what aligns the content. Without it, two contractors price different works under the same heading.
Common circulation is what aligns the information. Without it, some contractors price with data the others do not have.
These three alignments are the product of the package, not of the analyst's skill.
The case of unsolicited quotations
A frequent situation in private work and rarely addressed. It arises when contractors alter the price schedule.
A client who simply requests quotations, with no common package, receives documents structured differently.
Those quotations are not comparable, even though each carries a total.
Each contractor has defined its own scope, according to its understanding of the need and its commercial habits.
Comparing the totals then amounts to comparing three different projects, which has no economic meaning.
This is precisely the situation the schedule exists to avoid, as the article on measurement and the price schedule recalls.
What can still be salvaged
Four steps, where comparability was not built upstream. They restore a basis for comparison.
Draw up a mapping table, aligning the items of each quotation.
Identify works present in one and absent from another, and price them separately.
Request additions for the missing works, so as to reconstitute a common scope.
Give up comparing where differences of scope are too great, and re-tender on a common basis.
The fourth step is often the most economical, even if it looks expensive in time.
What comparability does not guarantee
Two limits.
It does not guarantee quality of execution, which turns on criteria other than price.
It does not guarantee the contractor's reliability, which is assessed separately.
Comparing comparable prices is a necessary condition of a good choice, not a sufficient one.
What this means for a professional
Four rules.
Build comparability into the package, not into the analysis table.
Refuse to compare unsolicited quotations without first bringing them to a common basis.
Price the differences of scope rather than ignoring them.
Recommend re-tendering where comparison is structurally impossible.
This article sets out a method of professional orientation. It reproduces no content from normative documents.