Where contradictions usually sit
A specification and a set of drawings are rarely written by the same person at the same time, so they drift apart, especially when there are revisions in between. The examples below are illustrative, but every estimator recognises the pattern.
| Type | Example | Where to look |
|---|---|---|
| Material | The specification asks for spruce, the elevation names thermally modified timber. | Façade chapter against elevations and materials schedule |
| Dimension | Batten spacing of 600 mm in the specification, 400 mm on the detail. | Specification against detail drawings |
| Quantity | The bill of quantities says 120 m² of façade, your take-off gives 135 m². | Bill against your own take-off or the model |
| Finish | Sills in RAL 7016 in the specification, RAL 9007 on the elevation. | Specification against colour schedule and elevations |
| Scope boundary between trades | The façade specification says scaffolding by others, the roofing specification says included. | General provisions against every work package |
| Revision | The specification refers to revision B, the drawing in the package is revision C. | Revision register and drawing title blocks |
How to find them systematically
Reading carefully is not enough, because you see what you expect to see. Taking off is itself a check: only when you pull a quantity from both sources do you see that they differ. A fixed order helps:
- For each element (front façade, side façade, roof edge, say), list material, size, colour, fixing and finish.
- Note the revision and date of every document so you know which is newer.
- Go through the sources and fill in your list, with clause and page.
- Compare the quantities in the schedule with your own take-off.
- Look at the boundaries between work packages: who supplies the sill, the roof edge, the scaffolding?
- Also look for what is stated nowhere. A missing detail is not a contradiction, but it is a question.
Distinguish a true contradiction from two values that can both be right: a minimum joint of 8 mm and one of 10 mm can coexist. Raising questions takes time, so keep your list sharp.
Recording and asking during the clarification round
Keep one line per finding: number, subject, source 1 (document, clause, page), source 2, what differs, your question, the answer and the date. Later you can show what your price rested on.
How to word the question
- Name both sources with clause and page or sheet.
- Describe what differs, without interpreting it.
- Ask for a choice: "Which of the two applies for pricing?"
- Bear in mind that answers are often shared with all tenderers. Do not give away your pricing strategy, and check the procedure in the tender documents.
Watch the question deadline: anything that arrives afterwards often goes unanswered. Start your list early.
If the answer does not come
If no answer comes, or it comes too late, you can include a reservation in your tender or keep a provisional sum. Whether that is allowed is set out in the tender documents, because some clients do not accept reservations. In any case, record which variant you priced and why, so a colleague or your director can find it later.
What it costs when you miss one
The amount depends on what differs and on your contract. An example with made-up figures: 150 m² of façade and a price gap of 18 euros per m² between two materials is 2,700 euros on one item. If you price the cheaper variant and the dearer one turns out to apply, you carry the difference unless you made a reservation or there is a variations clause. A missed scope boundary affects whole items, such as scaffolding. How to test subcontractor quotes against this is covered in Comparing subcontractor quotes.
What does the contract say?
Under UAV 2012, paragraph 2, sub-paragraph 4, contradictory parts of the specification are ranked: a newer written or drawn document prevails over an older one, a description prevails over a drawing and a special provision prevails over a general one. If that does not settle it, the contradiction is interpreted against the party who had the documents drawn up. Sub-paragraph 5 obliges the contractor to warn the client's supervisor of an evident contradiction.
This summarises the sources below. The contract documents of your project may deviate from UAV 2012 or may not apply it at all, so check the order of precedence in your own contract documents. This is not legal advice.
How Modou helps
Modou lays the specification, drawings and model side by side and flags where they contradict each other, with both sources shown. He does not pick a source himself; you do, and your reason is recorded. Modou notes questions for the architect, but you send them yourself. Read how it works or start with your project.
Read next
- Calculating net façade area: openings, reveals and cutting loss
- Comparing subcontractor quotes: scope first, then price