(pronounced uh-DEN-dum) Don’t feel “dum” if you don’t know this word. (That’s what we’re here for.) In the A&D world, an addendum is a change (or many changes that occur all at the same time) to a set of construction documents (drawings plus specifications) after they are already issued for bidding. Why would you ever need an addendum? Numerous reasons:

1) If a mistake(s) was made in the set of documents.
2) If the client changes the parameters of the project at the last minute.
3) If a code official makes a last minute ruling on a code compliance issue.
4) If the bidding contractors find significant gaps in / problems with / questions of the documents that need to be fixed / amended / tweaked.

After the addendum – or addenda, if there end up being more than one – is issued, then contractors can complete the bidding process, and the bid can be rewarded. All of the changes then become part of the completed drawing package that is used for construction.