In a construction bid you price every line of the bill of quantities. But the work you are contracting for is described elsewhere: in the technical specification and in the drawings. When the documents do not agree, someone pays the difference — and if nobody flagged it in time, it is often the bidder.
Three documents that must agree
- The specification says how the work is built: the contract clauses and the technical requirements for each item — materials, classes, testing, tolerances.
- The drawings say where and how much: the geometry the quantities come from.
- The bill of quantities says what gets paid for: each item, its unit and its quantity, with a price to be filled in.
A serious bid reads all three together. A price built on the bill alone trusts that whoever wrote it read the other two without error.
Where they usually diverge
- A specified requirement with no item in the bill. The specification calls for a test, a membrane, a treatment — and there is no line to price it.
- An item with no specification. The bill asks for “thermal insulation” and no document states thickness or material.
- Descriptions that do not match. Concrete class, wall thickness or window type say one thing in the bill and another in the specification or the drawings.
- Quantities that do not match the drawings — a design revision that never reached the bill, a floor measured twice, an element forgotten.
- Work “deemed included” that nobody measured. A description saying “including everything necessary” pushes into the price whatever the other documents failed to say.
- Lump sums where measurement was possible. A lump sum cannot be checked against the drawings, nor compared between bids.
In Portuguese public works, there is a deadline to say so
In Portuguese public tenders, the Public Contracts Code puts the three documents on the same table and sets a deadline to check them.
- The specification carries the detailed design and the bill of quantities. The law requires “a complete list of all types of work needed to build the project, and the corresponding bill of quantities” (article 43(4)).
- The bid prices that list: it must include “a list of unit prices for every type of work foreseen in the detailed design” (article 57(2)).
- Errors and omissions must be raised in the first third of the bidding period, in a list identifying them “expressly and unequivocally” (article 50(1)). The client rules on it by the end of the second third; anything not expressly accepted counts as rejected (article 50(5)).
- What went unsaid is paid half and half. The contractor bears half the cost of the extra work needed to make good errors and omissions it should have caught at bidding stage — except those it did list and the client did not accept (article 378(3)). Those only detectable at site handover must be claimed within 60 days (article 378(4)).
In a tender, checking the bill is not diligence: it decides who pays for what is missing from it.
In private work, it is in the contract — or nowhere
Private work has no timed errors-and-omissions stage like a public tender. What protects the bidder is what gets written down before the price is fixed: the questions, in writing, with the exact reference — bill item, drawing number, specification clause; the answers, attached to the bid; and, in the contract, which document prevails when they disagree and how work that none of them foresaw gets paid.
How to check, step by step
- Bill against specification, item by item. Every item needs its specification; every specified requirement needs its item.
- Bill against drawings, in the chapters that carry the price. You do not have to re-measure everything: re-measure the heaviest chapters and compare.
- Every discrepancy in a list, with the references of the documents involved and the difference found.
- The list goes out in writing, on time — within the procedural deadline in public work; before the price is fixed in private work.
- Whatever stays unanswered goes into the bid as a stated assumption, spelled out.
When the design comes in Revit or IFC
If the design was produced in a BIM model, step 2 changes in kind: instead of measuring by hand again, you take a second bill from the model itself, each quantity tied to the elements that produced it. The comparison with the tender bill becomes line by line, and each difference points at a specific element — which is what you can actually write in a list of errors and omissions.