How to read an addendum before you bid

An addendum is a change or clarification to the bid documents that the owner or consultant issues before bids close. It is numbered and dated, goes to everyone who took out the documents, and becomes part of the contract. For a sub, one addendum can move a wall type, add a floor of footings, or push the closing date. Missing one is how a bid ends up priced on drawings that no longer exist.

What an addendum contains

• A cover and a list of changes — by specification section and by drawing, each item numbered.
• Answers to bidders' questions — often the most useful part: clarifications that change scope without a new drawing.
• Revised or added specification sections, sometimes whole, sometimes as changed paragraphs.
• Revised or added drawings, reissued with a new revision in the title block.
• Changes to the instructions to bidders — a new closing date, site visit, or bid form.

Reading it, in order

1. Check you have them all. Addenda are numbered. If you have 1, 2 and 4, find 3 before anything else.
2. Read the list of changes first. Mark every item that touches your trade, including answers to questions.
3. Check the dates and the bid form. A moved closing or a replaced bid form is easy to miss inside an addendum about ceilings.
4. Open each revised sheet. Look for revision clouds and the delta symbol with the revision number, then the revision block in the title block. Clouds are drawn by hand and are sometimes missed, so compare the sheet itself where the change matters.
5. Read later addenda over earlier ones. Addendum 3 can undo part of Addendum 1.
6. Update the specifications too. A changed board type or concrete strength in the spec changes the price even when no drawing moved.

Carrying it into the takeoff

• Replace the sheets, don't layer them. Measure from the current revision only, and keep the superseded sheet for reference.
• Re-measure only what changed — but check that walls, footings or openings off the clouded area were not renumbered or retagged.
• Note each change against your quantities: “Add. 2, item 7: P3 now to deck — board +180 SF.” If the bid is questioned, that note is the answer.
• Watch schedule changes. A revised partition, footing or opening schedule changes every instance of that mark on every sheet, not just the clouded one.
• Acknowledge every addendum on the bid form, by number. Many forms make an unacknowledged addendum grounds to reject the bid.

After close

Changes after bids close are handled differently — by negotiation, a post-bid addendum to the bidders still in the running, or a change once the contract is signed. The same reading applies: find every change, and price only what it touched.

Doing it on the drawings

When you upload a revised set to PreConstruct AI, it compares the text on each sheet with the set it replaces, matched by sheet number, and reads only the sheets that changed. It lists what was added and removed and any quantity that moved, each linked to the sheet, and flags takeoff lines from changed sheets until you check them. It compares the text on the sheets, so a change drawn without any change to the words needs your eye too.