AI ESTIMATING · M&E
Short answer: Make every quantity in your takeoff point to its drawing sheet and revision from the start. When an addendum arrives, log which sheets it replaces, compare old and new revisions, and re-count only the lines that trace back to changed sheets. Everything else stays as it was, and you finish with a change list you can check before closing.
Why do addenda take so long to price?
It's a familiar week. You've finished the takeoff for a Level 1 to Level 5 office block, the BQ is half priced, and the main contractor issues Addendum 2 three days before the closing date. It includes revised lighting layouts for two floors, a new DB schedule and an updated FCU layout.
The slow part isn't the new drawings. It's not knowing which of your existing quantities they affect. If your takeoff doesn't record where each number came from, the safe option is to re-count everything on the affected disciplines. That's how a one-page addendum turns into two lost days.
What should I do first when an addendum arrives?
Before you open a single drawing, log what's arrived. A simple addendum register stops the most common mistake, which is pricing from a sheet that's been superseded.
| Addendum | Sheet | Old rev | New rev | Affects |
|---|---|---|---|---|
| Add. 2 | E-12 Lighting layout L2 | B | C | Lighting points, emergency lights |
| Add. 2 | E-31 DB schedule | A | B | DBs, submains |
| Add. 2 | M-03 FCU layout L3 | A | B | FCUs, refrigerant piping, condensate |
| Add. 2 | Spec clause, cable type | n/a | Revised | Cable descriptions, rates |
Include specification and BQ changes as well as drawings. A changed cable type in the specification can affect every line of your power BQ without a single drawing changing.
How do I find what changed between drawing revisions?
Start with what the consultant tells you, then check it.
- Revision clouds and the revision table. Most consultants cloud the changes and add a note to the title block. Read the note first.
- Don't rely on clouds alone. Clouds get missed, and sometimes a whole sheet is reissued with no clouds at all. Compare the old and new sheets side by side for anything unclouded.
- Check knock-on sheets. A moved DB on the layout may change submain lengths on the riser diagram. A relocated condensing unit on the roof plan changes refrigerant runs on the FCU layout.
- Write the changes down as a short list per sheet: "L2 east wing, 6 downlights added", "DB-2B moved to grid C4".
How do I update the BQ without re-counting everything?
This only works if each line of your takeoff already records its source sheet and revision. If it does, the method is straightforward:
- Filter your takeoff by sheet. Pull every line that traces to a revised sheet. On the example above, that's lines from E-12, E-31 and M-03, plus anything hit by the spec change.
- Re-count only those lines. Count from the new revision and record the new revision against each line.
- Leave untouched lines alone. If a line traces to a sheet that hasn't changed, its quantity stands.
- Check knock-on lines. Submains, containment and piping that run between areas often trace to more than one sheet.
- Produce a change list. Old quantity, new quantity, difference, and the sheet that caused it.
- Re-price only the changed lines with your own rates, and update the BQ total.
The change list is worth keeping. It gives your estimator something specific to check, and it gives you something to point to if the main contractor later queries why your price moved between submissions.
Can AI compare drawing revisions for me?
Yes, and it's one of the more useful things a properly set-up AI can do. Given the old and new revisions of a sheet, it can list what appears to have changed, re-count the affected items and produce the change list with sheet references.
Two cautions. First, it still needs your estimator to check the change list, because a small symbol moved on a dense sheet is easy for anyone to miss, AI included. Second, it only saves time if the original takeoff was built with sheet and revision on every line. A chatbot asked to "update my BQ for Addendum 2" with no traceable takeoff behind it has to start again, just as a person would.
In a UkurBQ setup, revised sheets are compared, changed lines are listed with the reason, and anything unclear, such as a change that isn't clouded, is marked for your estimator to check.
What if an addendum arrives very close to closing?
- Prioritise by value. Deal first with changes to high-value items: DBs, submains, chillers or VRF condensing units, inverters on solar jobs.
- Ask early. If the addendum is unclear, send the query to the main contractor straight away. Answers take time.
- Note assumptions. If you can't resolve something before closing, state your assumption in your submission rather than guessing silently.
- Acknowledge the addendum. Make sure your submission acknowledges every addendum received, as the tender documents require.
- Re-send supplier RFQs only for items whose quantity or specification changed.
FAQ
Do I need special software to track addenda?
No. A register in Excel and a takeoff where every line records its sheet and revision is enough to start. The discipline matters more than the tool.
What if the consultant doesn't cloud the changes?
Compare the full sheet against the previous revision. Unclouded changes are common enough that it's worth checking every reissued sheet, not only the clouded areas.
Should I re-count the whole floor to be safe?
Only if your takeoff can't tell you which lines came from which sheet. If it can, re-count the affected lines and check the knock-on items.
How do I show the main contractor what changed in my price?
Keep the change list with old and new quantities and the sheet behind each change. It makes queries quick to answer.
Try it on a tender you've already priced
Send one past tender. We return a draft BQ with every quantity traced to its sheet, so you can compare it with your own. Free, under NDA.
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