What an addendum can change
The architect or the owner issues addenda during the bid period. Each one has a number and a date. An addendum can be one page or several hundred.
- The bid date, time or place.
- A spec section: new text, deleted text or a full replacement.
- A drawing sheet: a revised sheet or a small sketch.
- The list of acceptable manufacturers, after substitution requests.
- Answers to bidder questions.
- Alternates, allowances or the bid form itself.
Why addenda matter to a takeoff
An addendum can add an item, remove an item or change a count. A revised gym plan can move a divider curtain or delete a scoreboard. If the takeoff was done before the addendum came out, the takeoff is now wrong. Late addenda cause many bid errors.
How to handle addenda
- Check the plan room for new addenda until the bid closes.
- Read every addendum in full, not only the pages that name your section.
- Mark each change on your copy of the spec and the sheets.
- Update the takeoff and write down which addendum caused each change.
- Acknowledge each addendum by number on the bid form or in your proposal.
Addendum, bulletin and change order
An addendum changes the documents before the contract is signed. After the contract is signed, changes come by other documents. Names vary by architect. Bulletin, supplemental instruction, proposal request and change order are common. Only an addendum is part of the bid.
If you miss one
Many bid forms require you to list each addendum. On public work, a bid that does not acknowledge an addendum can be rejected. The rule depends on the owner and the state. Read the instructions to bidders.
Takeoff Tool reads the bid packet for one trade, including the addenda you add to the upload.
Bid documents · Updated 11 Nov 2026