I (well, a contractor) added a new addition to my house, and the floor creaks when I walk on it. I crawled under the addition and identified the problem.
On each footing, there is a steel bracket that connects the footing to the beam it supports. The bracket is connected tightly with screws. At the site of the noise, there is a small gap (~3/8 in.) between the footing and the beam. In other words, the beam is floating slightly above the footing. Thus, this particular bracket makes a creaking noise when the beam moves.
The bracket doesn't move visibly... it just creaks.
I tried to fix the problem by stuffing shims into the gap, but it didn't really work. Depending on the temperature, the noise gets better or worse sometimes.
Any suggestions? Is it safe for me to DIY this? If I remove or replace the bracket, will the resulting beam movement cause damage to walls or windows?
Edit: Here's a photo from my latest repair attempt: https://imgur.com/a/KQkkpbY